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  • 1995-1999  (50)
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  • Inorganic Chemistry  (1.277)
  • Gas chromatography
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Materialart
Erscheinungszeitraum
  • 2020-2023
  • 1995-1999  (50)
  • 1980-1984  (793)
  • 1920-1924  (573)
Jahr
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    The isoprostanes: Unique bioactive products of lipid peroxidation (1998)
    Springer
    Journal of biomedical science 5 (1998), S. 415-420 
    Details
    ISSN: 1423-0127
    Schlagwort(e): Isoprostanes ; Oxidative stress ; Lipid peroxidation ; Gas chromatography ; Mass spectrometry ; Human disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The development of a specific, reliable and noninvasive method for measuring oxidative stress in humans is essential for establishing the role of free radicals in human diseases. Currently, accurate techniques to assess oxidant injury in vivo are extremely limited although a number of approaches are being investigated. Of these, the measurement of specific products of nonenzymatic lipid peroxidation, the F2-isoprostanes (F2-IsoPs), appears to be a more accurate marker of oxidative stress in vivo in humans than other available methods. The purpose of this brief review is to acquaint the reader with the IsoPs from a biochemical perspective and to provide information regarding the utility of quantifying these compounds as indicators of oxidant stress.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02255929
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  • 2
    Digitale Medien
    Digitale Medien
    Quantitative determination of carbohydrates in orange juice by gas chromatography (1998)
    Springer
    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 206 (1998), S. 48-51 
    Details
    ISSN: 1431-4630
    Schlagwort(e): Key words Carbohydrates ; Myo-inositol ; Orange juice quality ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract  A gas chromatographic method using a capillary column is described for the quantitative analysis of fructose, glucose, sucrose and myo-inositol in orange juice. The method is evaluated for precision and recovery using phenyl-β-glucoside as an internal standard. The results support the suitability of the method. Carbohydrates (fructose, glucose, sucrose and myo-inositol) were determined in different kinds of orange juice. The determination of carbohydrate composition and ratios of the carbohydrate constituents provide a method to assess orange juice quality, especially the myo-inositol content and myo-inositol/fructose ratio. These new indices, which were found to be lower in samples made from concentrates, provide information on the quality and genuineness of orange juice.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002170050212
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  • 3
    Digitale Medien
    Digitale Medien
    Amounts of conjugated linoleic acid (CLA) in German foods and evaluation of daily intake (1998)
    Springer
    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 206 (1998), S. 77-82 
    Details
    ISSN: 1431-4630
    Schlagwort(e): Key words Anticarcinogen ; CLA ; Conjugated linoleic acid ; Daily intake ; Foods ; Gas chromatography ; Lipids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract  The quantities of the biologically active isomer of conjugated linoleic acid (CLA) – C18:2 c9t11 – in 139 German foods were analysed by capillary gas chromatography (results are given as a % of all identified fatty acid methyl esters). The CLA content ranged from 0.40% (Gouda) to 1.70% (Jurassic cheese, Old Emmentaler) in dairy products, from 0.11% (rabbit) to 1.20% (lamb) in meat, and from 0.01% (pike-perch) to 0.09% (carp) in fish. CLA could be detected in neither vegetable fats or oils nor in margarines (CLA 〈0.01%). Crisps, chocolates, cakes and pastries, and other foods have only a negligible CLA content. The average estimated CLA intake in Germany was calculated to be 0.35g CLA/day for women and 0.43g CLA/day for men.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002170050218
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  • 4
    Digitale Medien
    Digitale Medien
    Comparison of gas chromatographic methods for analysis of butyric acid in milk fat and fats containing milk fat (1998)
    Springer
    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 206 (1998), S. 213-216 
    Details
    ISSN: 1431-4630
    Schlagwort(e): Key words Milk fat ; Mixed fat ; Milk fat content ; Butyric acid ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract  The analysis of butyric acid (C4) is of importance for the determination of the proportion of milk fat in mixed fats. Three gas chromatographic methods were compared with regard to their precision for the measurement of C4, i.e. analysis of butyric acid methyl ester after trans-esterification of fat by sodium methylate (method A) or trimethyl sulphonium hydroxide (method B), as well as analysis of free butyric acid (method C), using an internal standard with each method. The examination of 30 milk fats which varied greatly in terms of their C4 content, using methods A, B and C, resulted in mean values of C4 of 3.42 g/100 g fat, 3.71 g/100 g fat and 3.06 g/100 g fat, respectively. The value determined using method B seemed too high, and this may have been due to the presence of co-eluting artefacts, whereas the value determined using method C was clearly too low, and can probably be attributed to losses during sample preparation. The standard deviation (SD) of 0.015 obtained from repeated analyses using method A was quite good. Results obtained using methods B and C had SDs of 0.029 and 0.074, respectively. Different levels of free fatty acids did not affect the results obtained using method A. When method A was checked by analysis of the reference fat, CRM 164, the C4 level determined was found to deviate from the certified C4 content of 3.49 (± 0.06) g/100 g fat by only 0.05 g C4/fat 100 g. Thus method A proved the most suitable for the determination of the proportion of milk fat in mixed fats by analysis of butyric acid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002170050245
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  • 5
    Digitale Medien
    Digitale Medien
    Changes in free monosaccharides during storage of some UHT milks: a preliminary study (1998)
    Springer
    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 207 (1998), S. 180-181 
    Details
    ISSN: 1431-4630
    Schlagwort(e): Key words UHT milk ; Storage ; Monosaccharides ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract  Changes in the free monosaccharide fraction and non-casein nitrogen during the 3-month storage of five batches of commercial UHT milk were studied. Batches with high residual proteolytic activity showed a considerable increase in galactose, N–acetyl glucosamine and N–acetyl galactosamine levels during the storage period, whereas their glucose and myo-inositol contents remained unaltered. In batches with slight or negligible proteolytic activity no changes in the free monosaccharide fraction were observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002170050315
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  • 6
    Digitale Medien
    Digitale Medien
    Application of a new method for analysis of exhaled gas in critically ill patients (1998)
    Springer
    Intensive care medicine 24 (1998), S. 415-421 
    Details
    ISSN: 1432-1238
    Schlagwort(e): Key words Acetone ; Gas chromatography ; Isoprene ; Lipid peroxidation ; Microwave desorption ; N-pentane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Objective: Application of a new method for analysis of exhaled gas in critically ill patients. Design: Open study. Setting: Surgical intensive care unit of an university hospital. Patients: Thirty-seven consecutive, critically ill, mechanically ventilated patients. Interventions: None. Measurements and results: Chemical analysis of the patient's exhaled gas was based upon substance adsorption and concentration onto activated charcoal, microwave desorption and gas chromatographic separation. Patients with acute respiratory distress syndrome (ARDS) exhaled less isoprene than those without ARDS [9.8 (8.2–21.6) vs 21.8 (13.9–41.4) nmol/m2 per min [median (95 % confidence interval)], p = 0.04]. In patients who developed pulmonary infection, pentane elimination increased from 0.4 (0.0–5.4) to 2.7 (0.6–6.1, p = 0.05) nmol/m2 per min and isoprene elimination decreased from 5.2 (0–33) to 5.0 (0–17, p = 0.05) nmol/m2 per min, resulting in a significant increase in pentane/isoprene ratio from 0.1 (0–0.3) to 0.4 (0–15, p = 0.007) when compared to patients without pulmonary infection. Conclusions: The new method allows quantitative analysis of human gas samples with low substance concentrations and is well suited for clinical studies which involve the investigation of metabolic processes in the lung and the body.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s001340050589
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  • 7
    Digitale Medien
    Digitale Medien
    Large-volume PTV injection: Comparison of direct water injection and in-vial extraction for GC analysis of triazines (1998)
    Springer
    Chromatographia 47 (1998), S. 35-41 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Programmed-temperature vaporization (PTV) ; Large-volume injection ; Direct water injection ; Triazines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The potential of large-volume PTV injection was studied for the analysis of triazine herbicides in water samples. Direct water injection and in-vial extraction were described and compared. Detection limits were between 0.01–0.02 μg L−1 and relative standard deviations were 〈9%. Both methods are suitable for the analysis of triazines at ppt-level, although in-vial extraction is favourable for water samples with relatively large amounts of matrix components.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466783
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  • 8
    Digitale Medien
    Digitale Medien
    Development of gas chromatographic method for determination of cholesterol oxides in meat products (1998)
    Springer
    Chromatographia 47 (1998), S. 42-48 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Cholesterol oxides ; Cholesterol oxidation products (COPs) ; Meat products
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method of extraction, purification and gas chromatographic analysis of five cholesterol oxidation products (COPs) (7β-hydroxycholesterol, 5α, 6α-epoxycholesterol, 25-hydroxycholesterol, 7-ketocholesterol and cholestane-3β, 5α, 6β-triol) has been developed. The method is aimed at the determination of COPs in meat and meat products, in particular dry sausages, where large differences in the content of cholesterol and its oxidation derivatives may occur. Linearity of response of trimethylsilyl ethers was defined. The minimum concentration tested was 2.5 μg g−1 in the injected solution. The main feature of the present work is the addition of a purification step of unsaponifiables by SPE on silica cartridges. Extraction recoveries of COP standard mixtures, performed with or without the SPE step, are evaluated. The introduction of the clean-up step results in high purity samples without further losses in the entire process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466784
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  • 9
    Digitale Medien
    Digitale Medien
    Fast determination of VOCs in workplace air by solid-phase extraction and gas chromatography-mass spectrometry (1998)
    Springer
    Chromatographia 47 (1998), S. 57-62 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Solid-phase extraction ; Graphitized carbon black ; Volatile organic compounds ; Workplace air
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A fast, simple, and reliable method is presented for the determination of atmospheric semi-volatile organic pollutants at μg m−3 levels. The method has been used to monitor potentially carcinogenic toxic compounds to which workers are exposed in workplaces, and to measure the same compounds in outdoor air.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466786
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  • 10
    Digitale Medien
    Digitale Medien
    Interaction studies of vinychloride with liquid foods by gas chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 63-71 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Liquid foods ; Food packaging materials ; Vinylchloride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The interaction of vinylchloride (VC) with liquid foods, such as water, olive oil and honey, was studied using the relatively new technique of Reversed-Flow Gas Chromatography (RFGC). The RFGC method permits the calculation of the VC diffusion coefficient in the liquid phase (water, oil and honey) and the determination of the partition coefficient of VC between the liquid and the carrier gas, as well as the determination of the Henry's constant of VC in the liquid food. From the variation of the above parameters with temperature, thermodynamic parameters (free and excess free energies, enthalpies, entropies and activity coefficients) were calculated for the adsorption of VC by liquid foods. These are discussed in comparison with the same parameters calculated from empirical equations or determined experimentally by other techniques.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466787
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  • 11
    Digitale Medien
    Digitale Medien
    Fundamental relationships in gas chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 570-574 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Compressibility correction factor ; Specific retention volume
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The exact definition of the compressibility correction factor,j, has been extensively discussed in recent literature. In this work, it is shown that this compressibility correction factor has several different interpretations; however, the simplest and most useful meaning involves a correction from the experimentally accessible pressure at the outlet of a column to the average pressure in the column. Also, an unconventional definition of the retention volume of a solute in terms of the sample size and the equilibrium concentration of the solute in the mobile phase is presented. This retention volume definition is presented as an alternative to the common definition ofV R as the volume of carrier gas which passes through the column in a period of time called the retention time. In this discussion, it is emphasized that the temeprature dependence of the specific retention volume is determined by the thermodynamics of the phase distribution process for the solute and not by an equation-of-state for the carrier gas. Finally, the conventional correction of the specific retention volume by a factor of 273/T c can be used to correct a volume of carrier gas to a pseudo-standard state of 273 K and the average pressure in the column; however, this corrected specific retention volume has no relation to the specific retention volume that would be experimentally obtained at this standard state temperature and pressure. compressibility correction factor, and specific retention volume, were examined with regard to the physical interpretation, exact definition and appropriate standard states to be applied to these commonly reported chromatographic parameters. Such arcane discussions are beneficial to the health of science but may lead to confusion among potential and practicing chromatographers. In order to prevent or at least help ameliorate this problem, the following discussion presents a somewhat unorthodox interpretation of the questioned terms along with a pseudo-physical explanation of the so-called retention volume which is ubiquitous throughout the chromatographic literature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467497
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  • 12
    Digitale Medien
    Digitale Medien
    Determination of chlorobenzenes in environmental samples using solid phase microextraction, thermal desorption and analysis by gas chromatography coupled to FID, ECD, MSD, IRD detectors (1998)
    Springer
    Chromatographia 48 (1998), S. 74-80 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; SPME ; Soil and groundwater samples ; Chlorobenzenes ; Thermal desorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A complex method was developed for the determination of chlorobenzenes in soil and groundwater samples. Samples were taken at two sites in Baranya county, where a mixture of chlorobenzene waste was deposited, causing severe contamination in the environment. Clean-up of these sites demands modern and reliable analytical methods. Several sample preparation techniques were used, such as solid phase microextraction (SPME), supercritical fluid extraction (SFE), and a recently developed thermal desorption method. The applicability of various sample preparation methods was compared by measuring recovery percentages, relative standard deviations and by investigating the matrix dependency of these values. Gas chromatography was used for quantitative determination of chlorobenzenes, using MS, IR, FID and ECD detection techniques. Detection levels were as low as 1 ppt in water, and 10 ppt in soil samples. Chlorobenzene concentration was in the range 1 ppt-1 ppm in water and 100 ppb-100 ppm in soil samples. Identification and calibration of these compounds were performed by quantitative standards. This complex analytical method can be used for rapid and precise quantitative and qualitative determination of chlorobenzenes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467520
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  • 13
    Digitale Medien
    Digitale Medien
    Quantitative analysis of apolar polysiloxane phases in large-bore capillary columns (1998)
    Springer
    Chromatographia 47 (1998), S. 305-308 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Silicone phases ; Film thickness ; Large-bore capillary columns
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A technique is described for determination of the amount of bonded phase in commercial columns. It is adapted to the determination of the real nature and the thickness of a siloxane bonded film. Ten-centimeter samples of column are used. The method is tested for large-bore capillary columns. Applications to kinetic studies are suggested.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466536
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  • 14
    Digitale Medien
    Digitale Medien
    On-line sample treatment—capillary gas chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 313-345 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Sample pretreatment ; Coupling on-line to capillary GC ; Robotization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Sample pretreatment is often the bottleneck of a tracelevel analytical procedure. In order to increase performance, increasing attention is therefore being devoted to combining sample pretreatment on-line with the separation technique that has to be used. In the present review, a variety of procedures in use today for sample treatment coupled on-line to capillary gas chromatography (GC) is briefly discussed. Special attention is devoted to coupled-column techniques such as SPE-GC and LC-GC (SPE, solid-phase extraction; LC, column liquid chromatography) which are topics of much current interest, also because of their frequent use in so-called hyphenated systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466538
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  • 15
    Digitale Medien
    Digitale Medien
    Capillary gas chromatography of urinary steroids of terbutaline-treated asthmatic children (1998)
    Springer
    Chromatographia 48 (1998), S. 163-165 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Solid-phase extraction ; Urinary steroids ; Terbutaline treatment ; Asthmatic children
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Steroid metabolites have been measured by capillary gas chromatography in the urine of 38 children aged 3–6 years. The children comprised three groups: those with asthma being treated with Terbutaline (13), children with asthma but not undergoing treatment (17), and control children in hospital but free from endocrine diseases (8). There were significant (P〈0.05) differences between the amounts of steroids excreted by the different groups of children. Terbutaline therapy led to elevated levels of tetrahydrocortisone, androstenediol, 11-ketopregnanetriol and a reduced ratio of androgen to cortisol metabolites compared with those for untreated asthmatic children. We assume that Terbutaline does not have a steroid-like mechanism of action but acts by modification of the activity of several adrenocortical enzymes. We suggest a hypothesis whereby the antiasthmatic effect of Terbutaline could not only be a connected with its well-known mechanism of action, but it might be explained as a result of the modification of the production of certain glucocorticoids and androgen hormones.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467536
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  • 16
    Digitale Medien
    Digitale Medien
    Separation of positional isomers on polymeric calix[4]arene-siloxane stationary phases in capillary GC (1998)
    Springer
    Chromatographia 48 (1998), S. 422-426 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Calix[4]arene-tetramethyldisiloxane stationary phases ; Geometric and positional isomer separations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Poly(p-tert-butyldimethoxydipropyloxycalix[4]arene-tetramethyldisiloxane) (TBCX-TMDS) and poly(dimethoxydipropyloxycalix[4]arene-tetramethyl-disiloxane) (CX-TMDS), have been prepared and used as stationary phases for isothermal capillary gas chromatographic separations of positional isomers. Retention factors and separation factors for the isomers were measured. The isomers investigated were well-resolved on the two phases. Retention of all the solutes investigated is greater on TBCX-TMDS than on CX-TMDS, probably because of extra dispersive interactions of the solutes with thetert-butyl groups of the phase. Separation factors for closely-eluting isomer pairs are similar on the two phases. This seems to indicate either that the solutes are retained by non-inclusion processes or that if the isomer molecules do enter the cavity of the calixarene, i.e. the solute is retained by inclusion, thetert-butyl groups do not play a role in discriminating between the isomers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467714
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  • 17
    Digitale Medien
    Digitale Medien
    Determination of triethanolamine in air samples by gas chromatography-mass spectrometry (1998)
    Springer
    Chromatographia 48 (1998), S. 443-449 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Gas chromatography-mass spectrometry ; Triethanolamine in air
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Low amounts of triethanolamine, collected in ORBO 53 tubes during air sampling, required the development of a very sensitive method for determination. After desorption and silylation reaction with trimethylsilyl imidazole/trimethyl chlorosilane, the derivative was analyzed by gas chromatography-mass spectrometry on an Ultra 2 silica capillary column in single ion monitoring mode (retention time: about 6 min). The method has a detection limit of 1–2 pg with a desorption efficiency of about 81%. Linearity of response was ascertained in the ranges 10–100 ng and 100–1000 ng. Short-term method validation was carried out by intra- and inter-day assays on three amounts for each reference calibration curve. All results satisfied the pre-defined acceptance criteria. In general, the whole procedure was easily performed and was appropriate for our needs. Breakthrough volume was appropriate for our needs. Breakthrough volume was determined on authentic samples and was about 40–60 L, using a flow rate of 1 L·min−1. The amounts of triethanolamine found in the samples ranged from 150 to 250 ng (about 2.5–4.2 μg·m−3).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467718
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  • 18
    Digitale Medien
    Digitale Medien
    Monitoring of optical isomers of chiral alcohols and derivatives by chiral gas chromatography. Effect of derivatization on the enantio-differentiation (1998)
    Springer
    Chromatographia 48 (1998), S. 81-85 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Chiral separation ; Alcohols ; Diols ; Trimethylsilylation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Gas chromatographic chiral separation of several chiral 2-and 3-alkanols and diols was studied both in their free hydroxyl and in their trimethylsilyl ether forms. First, the derivatization procedure was verified through the identification of the trimethylsilyl ethers formed on the basis of their mass spectra and optimized to obtain quantitative reaction. The optimized procedure was applied to the trimethylsilylation of racemic mixtures of various hydroxyl compounds. The silylation was found to be highly effective in the improvement of the separation of the individual enantiomers. The major advantages of the derivatization process can be summarized as: (i) excellent baseline separation of the enantiomers of the silyl ethers was achieved in contrast to the parent OH-containing compounds, (ii) the sensitivity of detection highly increased, (iii) the separations do not show any significant concentration dependence and finally (iv) the analysis time needed decreased significantly.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467521
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  • 19
    Digitale Medien
    Digitale Medien
    Data correlation in on-line solid-phase extraction-gas chromatography-atomic emission/mass spectrometric detection of unknown microcontaminants (1998)
    Springer
    Chromatographia 48 (1998), S. 273-283 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Atomic emission and MS detection ; Solid-phase extraction ; Aqueous samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A procedure is described for the (non-target) screening of hetero-atom-containing compounds in tap and waste water by correlating data obtained by gas chromatography (GC) using atomic emission (AED) and mass selective (MS) detection. Solid-phase extraction (SPE) was coupled on-line to both GC systems to enable the determination of microcontaminants at the 0.02–1 μg L−1 level in 7–50 mL of aqueous sample. The screening was limited to compounds present in at least one heteroatom-selective GC-AED trace above a predetermined concentration level. These compounds were identified by their partial formulae (AED) and the corresponding mass spectra, which were obtained from the GC-MS chromatogram via the retention index concept. The potential of the approach was demonstrated by the identification of target compounds as well as all unknowns present in tap and waste water above the predetermined threshold of 0.05 μg L−1 (tap water) or 0.5 μg L−1 (waste water).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467683
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  • 20
    Digitale Medien
    Digitale Medien
    Crown ether capped cyclodextrin used as stationary phase for capillary gas chromatography (1998)
    Springer
    Chromatographia 48 (1998), S. 817-822 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Crown ether capped cyclodextrin ; Chiral separations ; Isomer separations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The solution of a new synthesized compound, mono-6-(1'-benzo-aza-15-crown-5)-2, 3, 6- permethyl-β-cyclodextrin, in the moderately polar polysiloxane OV-1701 was coated onto fused silica capillary column. The chromatographic characteristics including column efficiency, polarity and selectivity were studied. Excellent selectivity for the separation of enantiomers and positional isomers was obtained. The results show that the combined effect between the special caves of β-cyclodextrin and crown ether plays a significant role in the separation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467654
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  • 21
    Digitale Medien
    Digitale Medien
    Gas chromatography with UV-vis molecular absorption spectrometry detection: Data acquisition and treatment when using a diode-array spectrophotometer (1998)
    Springer
    Chromatographia 48 (1998), S. 535-541 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; UV-Vis detection ; Gas phase absorption spectrometry ; Alcohols
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary This article describes a theoretical/practical study of the parameters which affect the chromatograms obtained when using a molecular diode-array spectrometer as the detector in gas chromatography. The objective is to offer some rules which permit the identification of the optimum signal/noise relation. To achieve this, we study the effect of the different parameters which affect the noise and how to reduce their impact, as well as alternatives for increasing the signal. All the options tested can be applied by correctly programming the spectrometer with BASIC programs, within reach of any use who has even a small understanding of programming. Finally, we consider the effect that the selection of the acquisition conditions may have on the chromatographic resolution. All the studies are carried out using a mixture of alcohols and phenols.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466646
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  • 22
    Digitale Medien
    Digitale Medien
    Synthesis of a new liquid crystal, 4-[(4-chlorobenzyl)oxy]-4′-cyanoazobenzene and its use as stationary phase in gas-chromatography (1998)
    Springer
    Chromatographia 48 (1998), S. 427-430 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Liquid crystal stationary phase ; Packed columns
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The separation ofm-, p-, o- xylenes andm-, p- ethyltoluenes was studied on a packed column with 2,5% of 4-[(4-chlorobenzyl)oxy]-4′-cyanoazobenzene (CBOCA) on Chromosorb W HP 100–120 mesh. The synthesis and study of the mesomorphic behaviour of CBOCA are presented. Temperature range for the separation ofm-, p-, o- xylenes (in this order of elution) is 125–85°C, at cooling. The best separation was achieved at about 90°C. The separation temperature domain ofm-ethyltoluene fromp- ethyltoluene is 160–85°C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467715
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  • 23
    Digitale Medien
    Digitale Medien
    Derivatization of aromatic amines with bromine for improved gas chromatographic determination (1998)
    Springer
    Chromatographia 48 (1998), S. 436-442 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Water analysis ; Derivatization with bromine ; Aromatic amines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary For improved determination of aromatic amines by gas chromatography and detection with an electron capture detector (GC-ECD) a derivatization method based on the bromination of the aromatic ring in an acetic acid medium was developed. In general, all free ortho and para-positions relative to the amino group undergo electrophilic substitution. Separation of at least 30 compounds in a single chromatographic run in 30 min is possible. With this method, 56 aromatic amines were studied and only in 6 cases were no derivatives obtained. Quantitation limits determined from calibration data are 1.2–40 μg L−1 for a 100 mL sample and an injection volume of 1 μL. Previous experiments suggest that both sample and injection volume may be increased to lower the quantitation limit.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467717
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  • 24
    Digitale Medien
    Digitale Medien
    Effect of organic matter content in the trace analysis of triazines in various types of soils with GC-NPD (1998)
    Springer
    Chromatographia 48 (1998), S. 450-456 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Soil samples ; Microwave-assisted solvent extraction ; Nitrogen detection ; Triazine herbicides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Recent work demonstrated that the combination of microwave assisted solvent extraction (MASE) and capillary gas chromatography with selective nitrogen detection (GC-NPD) is a viable approach for the efficient determination of triazine herbicides in soils. However, for soils with a high organic matter content or the injection of more concentrated extracts to obtain lower LOD's the performance of gas chromatographic analysis of uncleaned extracts is hampered. This results in both a decrease of the chromatographic response of analytes and a decrease in the life time of the column due to coextracted matrix substances. The effect of various types of soils on the chromatographic analysis of triazine herbicides was studied. It appeared that for the investigated samples with an organic matter content below 5% processing of uncleaned extracts is possible. Samples with a higher organic matter content required a cleanup step. A rapid procedure on 100 mg silica cartridges has been developed using solvents compatible with the MASE extracts and the instrumental analysis. Beside the testing with different standard soils, about 120 samples of an ongoing monitoring program involving three different types of soil (organic matter content: 3–37%) were analysed. The selected compounds atrazine, desethylatrazine, desisopropyl-atrazine and simazine could be assayed in the various soil types to a level of at least 2 μg kg−1. For soil samples with a high organic matter content (〉5%), the rapid cleanup procedure allowed the trace analysis of the triazines and considerably increased the life time of the capillary column. Recoveries at levels from 2 to 50 μg kg−1 ranged from 70 to 100% with RSDs ranging from 5.1 to 9.5%. Confirmation of positive samples was carried out by gas chromatography mass spectrometry.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467719
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  • 25
    Digitale Medien
    Digitale Medien
    Identification and semi-quantitative determination of a migration contaminant from beverage carton packages into mineral water by on-line solid phase extraction gas chromatography-mass spectrometry (SPE-GC-MS) (1998)
    Springer
    Chromatographia 48 (1998), S. 581-583 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; On-line SPE-GC-MS ; Beverage carton packages ; Contaminant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An unknown migration contaminant was found in a number of mineral water samples contained in beverage carton packages. This compound was isolated by a fully automatic solid phase extraction system and identified by means of GC-MS as 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) [126-86-3], which is used as a surfactant in water-based printing inks and migrates during the production of the beverage carton material into the inner polyethylene film and subsequently into the product. The determined concentrations of TMDD ranged up to more than 50 μg L−1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466653
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  • 26
    Digitale Medien
    Digitale Medien
    Direct solid-phase microextraction combined with gas and liquid chromatography for the determination of lidocaine in human urine (1998)
    Springer
    Chromatographia 47 (1998), S. 678-684 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Column liquid chromatography ; Solid-phase microextraction ; Local anaesthetic lidocaine ; Optimisation of extraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Solid-phase microextraction (SPME) has been combined with gas chromatography (GC) and liquid chromatography (LC) for the determination of lidocaine in human urine. A polydimethylsiloxane (PDMS) coated fibre was directly immersed into buffered urine. Extraction conditions such as time, pH, ionic strength, temperature, and agitation were optimised. The extracted lidocaine was thermally desorbed in a split/splitless injector for analysis with a GC-FID system or desorbed with liquid in a specially designed SPME-LC interface for analysis with an LC-UV system. After optimisation the method developed was evaluated and validated. Extraction yields of 22% were obtained in about 45 min. The reproducibility of the method is 〈5% (relative standard deviation). For five-times diluted urine, linear ranges were found from 5–1000 and 25–1000 ng·mL−1 for SPME-GC and SPME-LC, with detection limits of 5 ng·mL−1 for SPME-GC and 25 ng·mL−1 for SPME-LC. SPME can be used as a simple sample pretreatment method for the determination of lidocaine in urine by GC and LC.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467453
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  • 27
    Digitale Medien
    Digitale Medien
    Investigation on five novel substituted β-cyclodextrins used as GC stationary phases (1998)
    Springer
    Chromatographia 47 (1998), S. 557-564 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Stationary phases ; β-Cyclodextrin derivatives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Five β-cyclodextrin derivatives, heptakis[2,6-di-O-pentyl-3-O-(4-nitrobenzyl)-β-CD (CD-I), heptakis [2,6-di-O-pentyl-3-O-(5-hexenyl)]-β-CD (CD-II), heptakis-(2, 6-di-O-cinnamyl-3-O-methyl)-β-CD (CD-III), heptakis-(2, 6-di-O-cinnamyl-3-O-acetyl)-β-CD (CD-IV) and heptakis(2, 6-di-O-cinnamyl-3-O-trifluoroacetyl)-β-CD (CD-V), were synthesized and coated on fused-silica capillary coluns. Their chromatographic characteristics were tested and compared with heptakis (2,3,6-tri-O-pentyl)-β-CD (CD-VI) and heptakis (2,6-di-O-pentyl-3-O-trifluoroacetyl)-β-CD (CD-VII). It was found that the size, polarity, and aromatic property of the substituted group at the 3-position of heptakis (2,6-di-O-pentyl)-β-cyclodextrins greatly influenced their chromatographic properties and separation ability. The introduction of aromatic group or a group containing a double-bond may bring π-π interactions between the host and guest molecules, and therefore increased the separation ability of the β-CDs for substituted benzene isomers. Introduction of cinnamyl groups in to the 2,6-3-position of β-CD has a significant effect on the chromatographic properties of the stationary phases(CD-III-CD-V).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467495
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  • 28
    Digitale Medien
    Digitale Medien
    Determination of heats of vaporization and gibbs free energies of alkylbenzenes on GC stationary phases of different polarity (1998)
    Springer
    Chromatographia 48 (1998), S. 89-94 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Heats of vaporization ; Gibbs free energies ; Kováts retention indices ; Alkylbenzenes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary In our paper we propose a new method for the determination of heats of vaporization (ΔH vap(i)) and the Gibbs free energies of vaporization (Δμp(i)) for individually selected alkylbenzenes, chromatographed on stationary phases of low and medium polarity. The method is based on a new thermodynamic description of the Kováts retention index (I (i)) making use of Trouton's rule. In fact, we attribute physical significance to two empirical relationships, well known from the literature. We can describe thermodynamically the magnitude ofI (i) using two relations, each of them potentially useful for further determination of δH vap(i) and Δμp(i). A comparison was made of the results obtained with the use of our new approach and of those already existing in the literature attained in a completely different way. The comparison suggests that the calculated δH vap(i) and Δμp(i) values are thermodynamically acceptable and hence correct, and the data suit into the series of similar values determined on stationary phases of different polarity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467523
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  • 29
    Digitale Medien
    Digitale Medien
    Separation of polychlorinated biphenyls from chlorinated pesticides using aminopropyl bonded-phase cartridge and determination by GC-ECD (1998)
    Springer
    Chromatographia 48 (1998), S. 293-298 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Solid phase extraction ; Polychlorobiphenyls ; Clorinated pesticides ; Organochlorine separation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Gas chromatography of polychlorinated biphenyls and chlorinated pesticides in water samples is carried out after adsorption from a 25–500 mL sample, on a cartridge containing 100 mg aminopropyl-bonded porous silica. The clean-up step in which the PCBs and chlorinated pesticides are separated in different eluates is achieved by passing 25 mL of 40% aqueous methanol through the NH2 Sep-Pak cartridge. The PCBs are desorbed with 500 μL ethylacetate, which is concentrated and analysis by GC-ECD. The average recovery, at 1 ppb is 〉97% with a standard deviation 〈2. The limits of detection are 0.1 ng μL−1 and 5 pg μL−1 respectively for Cl3-PCB and Cl8-PCB congeners. In the separation of PCBs from the chlorinated pesticides tested in this work, only the Aldrin is adsorbed for 60% with the PCBs by the NH2 Sep-Pak cartridge. The method described is rapid, simple and reproducible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467685
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  • 30
    Digitale Medien
    Digitale Medien
    Characterisation of GC stationary phases in multilinear retention model (1998)
    Springer
    Chromatographia 48 (1998), S. 728-738 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Stationary phases ; Prototypical phases ; Retention model ; Retention value ; Dipolarity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Stationary phases are characterised in a multilinear retention model by retention data of a set of selected prototypical substances. Prototypical stationary phases confirm the application of prototypical substances in the retention model. For comparison, 27 stationary phases are characterized with solute descriptors of the solvation model. New adjusted substance factors are calculated for 33 selected compounds for a new characterization of GC stationary phases in the extended retention model with retention values, calculated from retention indices and b-values of the n-alkane equation. Substance dipolarityD N-factors are separated from πN, the adjusted dipolarity-polarisability. New substance factors give satisfying correlation results and new explanatory factors as phase descriptors for 27 stationary phases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467640
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  • 31
    Digitale Medien
    Digitale Medien
    Precision of milk fat quantitation in mixed fats by analysis of butyric acid (1998)
    Springer
    Chromatographia 48 (1998), S. 758-762 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Butyric acid ; Milk fat content ; Mixed fats
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Quantitation of the milk fat content in mixed fats is of interest in food analysis. It can be achieved by calculation from the butyric acid (C4) content in the mixed fat and a mean C4 content for pure milk fats. Alternatively, instead of applying a C4 mean value, the C4 content in the actual milk fat can be used if this reference sample is available. A recently improved analytical method based on gas chromatography of butyric acid methyl ester using an internal standard has been applied to determine the milk fat content in mixtures with beef tallow, lard, soybean oil, olive oil, sunflower oil, palm kernel oil and palm oil ranging from 1 to 90% milk fat content. Within the whole range of mixtures, mean absolute deviations between the determined and the actual milk fat content were below 0.5% and the maximum absolute deviation was not more than 1.0% when using the reference sample. The overall mean absolute deviation was 0.04% for milk fat contents of 1 to 10% and 0.28% for milk fat contents of 10 to 90%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467644
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  • 32
    Digitale Medien
    Digitale Medien
    Determination of acids in Brazilian sugar cane spirits and other alcoholic beverages by HRGC-SPE (1998)
    Springer
    Chromatographia 48 (1998), S. 751-757 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Solid phase extraction ; Brazilian sugar cane spirit ; Lower fatty acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A gas chromatographic method for the analysis of seventeen acids in a water/ethanol matrix is described. The diluted samples were first concentrated by solid phase extraction. Nonanoic acid was the internal standard. A good separation profile was obtained for all compounds, including the isomers: n and iso-butyric acids, n and isovaleric acids and n and iso-caproic acids. The method is fast, sensitive (20–30 μg L−1) and has a good reproducibility (4–7 %). The recovery was in the range of 94%–116% for the medium chain acids (C7-C16). This method allowed the identification of fourteen acids in caninhas and other spirits. The total acid content and the profile of the exportation type caninhas are similar to the ones obtained for several international beverages.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467643
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  • 33
    Digitale Medien
    Digitale Medien
    Gas chromatography with UV-vis molecular absorption spectrometry detection: Increasing sensitivity of the determination of alcohols and phenols by derivatization (1998)
    Springer
    Chromatographia 48 (1998), S. 542-547 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; UV-Vis detection ; Gas phase absorption spectrometry ; Derivatization ; Alcohols and phenols
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method is proposed for the determination of alcohols and phenols based on their derivatization to benzoates and gas chromatography-gas phase molecular absorption spectrometry. All parameters affecting the derivatization reaction, such as the solvent, basic medium, benzoyl chloride and stirring time, were optimized. Chromatographic and instrumental conditions were also studied. Finally, a calibration study was performed and the results were compared to that obtained by the direct determination of the compounds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466647
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  • 34
    Digitale Medien
    Digitale Medien
    Gas chromatography analysis of organophosphorous pesticides in plant samples (1998)
    Springer
    Chromatographia 48 (1998), S. 156-157 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Gel permeation chromatography ; Organophosphorous pesticides ; Plant samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The work presents a GC method for the determination of six organophosphorous pesticide residues in cabbage. Chopped cabbage was blended with acetone, then extracted with the mixture of n-hexane:methylene chloride (1:1). The extract was purified on a GPC column packed with BioBeads SX-3 gel. The pesticides were eluted with the mixture of methylene chloride:cyclohexane (1:1) at the flow rate of 0.5 mL min−1. After concentrating the extract was analysed by GC. Nearly 100 samples of cabbage were analysed; trace residues of dimethoate (about 0.05 ppm) were found in 10 samples. The average recoveries of the pesticides were above 80% with a relative standard deviation mostly less than 10%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467534
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  • 35
    Digitale Medien
    Digitale Medien
    Gas chromatographic determination of major sterols in edible oils and fats using solid-phase extraction in sample preparation (1998)
    Springer
    Chromatographia 48 (1998), S. 745-750 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Solid-phase extraction ; Rapeseed oil ; Sterols
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A capillary gas chromatographic method is described for the determination of major plant sterols and cholesterol in edible oils and fats. In the sample preparation procedure reversed-phase, solid-phase extraction with C18 adsorbent was used to extract the unsaponifiable matter and for sample cleanup after saponification. Sterols were quantitated as their trimethylsilylether derivatives using an internal standard method (betulin). The method was validated by recovery tests and analysis of two reference materials representing vegetable oil mixture and milk fat matrices. Average recoveries of spiked cholesterol and cholesterol acetate in rapeseed oil were 103±4% (n=12) and 101±3% (n=10), respectively. The sterol values determined in the reference materials were found to be in a good agreement with their given certified or indicative values. Applied to edible oils and fats, plant sterols and cholesterol at levels〉20 mg kg−1 could be accuratively quantitated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467642
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  • 36
    Digitale Medien
    Digitale Medien
    Headspace gas chromatography analysis of toxic contaminants in ethoxylated alcohols and alkylamines (1998)
    Springer
    Chromatographia 48 (1998), S. 299-304 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Headspace sampling ; Ethoxylated alcohols ; Ethoxylated alkylamines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Headspace-gas chromatography was used to determine the contents of toxic 1,4-dioxane, ethylene oxide and ethylene glycol in ethoxylated alcohols and alkylamines, and in commercial cosmetics and washing products. A Permaphase PEG capillary column was used for the determination of 1,4-dioxane and ethylene oxide and a DB-17 column for ethylene glycol determination. Dimethylformamide was used as the solvent in the determination of 1,4-dioxane and ethylene oxide, and undecanol in the case of ethylene glycol. The detection limits for ethylene oxide, 1,4-dioxane and ethylene glycol are 1,2 and 10 μg·g−1, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467686
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  • 37
    Digitale Medien
    Digitale Medien
    Calix[4]arene derivatives as stationary phases for capillary gas chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 689-694 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Stationary phases ; Calix[4]arene derivatives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Two new kinds of calix[4]arene derivatives, 5,11,17,23-tetra-tert-butyl-25,27-bis(isopropylcarbamoyl-methoxy)-26,28-diundecenyloxy calix[4]arene (C[4]A) and 25,27-dibutoxy-5,11,17,23-tetra-tert-butyl-26,28-diundecenyloxy calix[4]arene (C[4]B), have been synthesized for use as stationary phases in capillary gas chromatography with OV1701. These stationary phases demonstrate high column efficiencies, wide operating temperature ranges, good thermal stability and excellent selectivity for aromatic isomers, especially phenol compounds. Their inclusion properties are also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467455
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  • 38
    Digitale Medien
    Digitale Medien
    Comparison of methods for prediction of the retention data of aromatic hydrocarbons on UCON LB 550X and on polydimethylsiloxane (1998)
    Springer
    Chromatographia 47 (1998), S. 721-723 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Correlation equation ; Alkylbenzenes ; Naphthalenes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A detailed statistical analysis is presented for comparing the validity of selected literature-recommended equations with the unified retention index concept for calculating the retention indexes of alkylbenzenes on UCON LB 550X and naphthalenes on polydimethylsiloxane. Comparison with literature sources shows that the unified retention index provides the smallest residual error for a set of aromatic hydrocarbons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467460
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  • 39
    Digitale Medien
    Digitale Medien
    Quantitative analysis of residual synthetic polystyrene adsorbent in drugs by curie-point pyrolysis gas chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 203-208 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Pyrolysis GC ; Residual polystyrene ; Streptomycin ; Vitamin B1
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Residual synthetic adsorbent, cross-linked polystyrene, used in drug purification has been analyzed quantitatively by Curie-point pyrolysis gas chromatography. The peaks of intact polystyrene adsorbent in the pyrogram were used as key peaks for quantitative measurement of residues of the adsorbent in vitamin B1 and streptomycin sulfate. It was shown that them-ethylstyrene orp-ethylstyrene peaks in the pyrolyzates were suitable for determination of polystyrene adsorbent content. The levels of residual adsorbent in the drugs were found to be 〈0.1 %, the value stipulated by the International Conference on Harmonization (ICH). In quantitative evaluation of an adsorbent content of 0.1 % the precision was 3.6 % and 2.7 % for vitamin B1 and streptomycin sulfate, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466582
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  • 40
    Digitale Medien
    Digitale Medien
    Retention indices of alkenes and the corresponding epoxides on a capillary column coated with cyanopropyl methyl silicone phase (1998)
    Springer
    Chromatographia 47 (1998), S. 230-233 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Alkenes ; Epoxides ; Retention index
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Retention indices or five 1-alkenes, seven branched alkenes and five cycloalkenes and the corresponding epoxides were determined at two temperatures on a fused-silica capillary column coated with cyanopropyl methyl siloxane to interpret their chromatographic behaviour. The standard deviation was 0.2 index units.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466587
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  • 41
    Digitale Medien
    Digitale Medien
    Determination of safrole in differentAsarum species by headspace gas chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 685-688 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Headspace sampling ; Safrole ; Asarum species
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The development of a headspace GC method (HS-GC) to determine the safrole content in differentAsarum species from China and Europe, using eugenol as internal standard, is presented in this paper. The best results could be achieved by thermostating the samples at 100°C for 30.0 min, adding 10 μL of water to each sample. Optimum pressurisation and injection time showed to be 3.0 min and 12 s, respectively. GC separation was performed on an SE-54 column. The HS-GC results for safrole were in good agreement with those obtained by direct GC analysis of the dichloromethane (DCM) plant extracts. The investigated Asarum samples showed great deviations concerning the safrole content even within the sameAsarum species, e.g.Asarum himalaicum from Sichuan contained 0.0051% of this compound, the same species from the province of Hebei 0.53%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467454
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  • 42
    Digitale Medien
    Digitale Medien
    Gas chromatographic analysis of phthalate esters in plastic toys (1998)
    Springer
    Chromatographia 47 (1998), S. 724-726 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Phthalate esters ; PVC ; Plastic toys
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method for the analysis of 10 phthalate esters in plastic toys is described. The samples are soxhlet extracted in dichloromethane and phthalate esters in the extract are analysed by GC. Detection limits of dimethyl phthalate, diethyl phthalate, dibutyl phthalate, bis(2-ethylhexyl) phthalate, di-n-octyl phathalate, di-n-nonyl phthalate, benzyl butyl phthalate and benzyl octyl phthalate were approximately 5 ppm. The detection limits of diisononyl phthalate and diisodecyl phthalate, which are mixtures of several isomers, were approximately 200ppm. Analysis of 17 plastic toys revealed that only PVC-toys contained phthalate esters. Bis(2-ethylhexyl) phthalate, diisononyl phthalate and diisodecyl phthalate in concentrations up to 40% were present in the PVC-toys.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467461
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  • 43
    Digitale Medien
    Digitale Medien
    Analysis of cyanide in blood by headspace solid-phase microextraction (SPME) and capillary gas chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 209-214 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Solid-phase microextraction ; Headspace sampling ; Cyanide in blood
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Cyanide can be extracted from whole blood samples by headspace solid-phase microextraction (SPME) with a Carbowax/divinylbenzene-coated fiber. During heating a vial of a whole blood sample containing cyanide and acetonitrile as internal standard (IS) at 50°C in the presence of Na2SO4, a Carbowax/divinylbenzene-coated SPME fiber was exposed in the headspace of the vial for 45 min to allow adsorption of cyanide and IS. The fiber needle was then injected into a capillary gas chromatography (GC) instrument equipped with nitrogen-phosphorus detection. The headspace SPME-GC with a Supel-Q PLOT fused silica capillary column gave large peaks for cyanide and IS; almost no interfering peaks appeared. Recoveries of cyanide dnd IS from human whole blood were 3.02–4.06% and 0.21%, respectively. The calibration curve for cyanide added to human blood showed excellent linearity in the range of 0.04–4.0 μg mL−1; the detection limit was about 0.02 μg mL−1. The coefficients of intra-day and inter-day variation were not greater than 7.1 and 9.2%. Good correlation (r 2=0.999) was found between the present SPME-GC method and the conventional microdiffusion colorimetric method. Data on determination of cyanide in rat blood after intraperitoneal administration are also presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466583
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  • 44
    Digitale Medien
    Digitale Medien
    Synergistic effects in mixed gas chromatographic stationary phases consisting of dibenzo-18-crown-6 and MPBHpB (1998)
    Springer
    Chromatographia 47 (1998), S. 575-578 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Mixed stationary phases ; Dibenzo-18-crown-6 ether ; MPBHpB ; Synergistic effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The synergistic effect is investigated in mixed gas chromatographic stationary phases containing dibenzo-18-crown-6 +MPBHpB [o-methyl-p-phenylene-bis-(p-heptoxy benzoate)], [o-methyl-p-phenylene-bis-(p-heptoxy benzoate)], with benzene/cyclohexane, cyclokexanes, phenols, alcohols and aniline derivatives as sample compounds pairs. Some of the separations reveal positive or negative synergistic effect. This effect depends on the temperature, the mixing ratio and the linear velocity of the carrier gas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467498
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  • 45
    Digitale Medien
    Digitale Medien
    Sulfuric acid pretreatment for the simultaneous GC screening of organochlorine and organophosphorus pesticides in herbal essential oils (1998)
    Springer
    Chromatographia 47 (1998), S. 587-592 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Organochlorine and organophosphorus pesticides ; Herbal medicine ; Essential oils ; Sulfuric acid treatment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A rapid and new clean-up method utilizing sulfuric acid treatment is demonstrated to identify and quantify the level of organochlorine (OC) and organophosphorus (OP) pesticide residue concentrations in herbal essential oils by gas chromatography (GC). Essential oils fortified with pesticides, that are extracted from herbs by steam distillation are partitioned with 65% acetonitrile/water(v/v) and treated with sulfuric acid at different reaction times and sulfuric acid concentrations. Optimal conditions, to avoid interference from essential oils in gas chromatographic analysis, is 17% (v/v) of a mixed phase ratio of sulfuric acid to organic solvent (hexane/ethyl ether=9∶1, v/v) and a reaction time of 30s. The response of the flame ionization detector (FID) is linear for all pesticides determined. Recovery of pesticides from fortified herbs studied are in the range of 75% to 111% (RSD, 4% to 11%) for OC, and 72% to 116% (RSD, 2% to 11%) for OP. Although sulfuric acid treatment destroys carbamate and some organophosphorus pesticides, this method has efficiently reduced matrix interference and provides a rapid, economical clean-up method with excellent linear data having low coefficients of variation for the GC analyses of BHC isomers, DDD, DDE, DDT, chlorothalonil, chloropyrifos, tetradifon, fenitrothion, malathion, and parathion in matrices of herbal essential oils.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467500
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  • 46
    Digitale Medien
    Digitale Medien
    Enantiomeric separation of unusual secondary aromatic amino acids (1998)
    Springer
    Chromatographia 48 (1998), S. 53-58 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Gas chromatography ; Enantiomeric separation ; Chiral derivatization ; Unusual secondary aromatic amino acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary High-performance liquid chromatographic and gas chromatographic methods were developed for the separation of unusual secondary aromatic amino acids. Amino acids containing 1,2,3,4-tetrahydroisoquinoline, 1,2,3,4-tetrahydronorharmane-1-carboxylic acid and 1,2,3,4-tetrahydro-3-carboxy-2-carboline moieties were synthetized in racemic or chiral forms. The high-performance liquid chromatography was carried out either on a teicoplanin-containing chiral stationary phase or on an achiral C18 column. In the latter case the diastereomers of the amino acids formed by precolumn derivatization with the chiral reagents 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate or 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide were separated. The gas chromatographic analyses were based on separation on a Chirasil-L-Val column.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467516
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  • 47
    Digitale Medien
    Digitale Medien
    Urinary steroid analysis of women with effluvium (1998)
    Springer
    Chromatographia 48 (1998), S. 86-88 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Solid phase extraction ; Methoxime-silyl derivate ; Urinary steroids ; Women with effluvium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Urinary steroid metabolites were measured by capillary gas chromatography in 25 women (aged 33.3±12.0 years) with effluvium and 16 control healthy laboratory workers women (aged 34.6±8.4 years). There was significant elevation in the level of a number of steroids and steroid metabolites. The elevation of most steroid metabolites refers to the increased steroid secretion of the adrenal and the high cortisol metabolites levels may be do to stress in some of the patients with effluvium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467522
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  • 48
    Digitale Medien
    Digitale Medien
    Enantioseparation of the compounds of technical toxaphene (CTTs) on 35% heptakis (6-O-tert-butyldimethylsilyl-2,3-di-O-Methyl)-β-cyclodextrin in OV1701 (1998)
    Springer
    Chromatographia 47 (1998), S. 565-569 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Chiral stationary phases ; Enantioseparation ; Toxaphene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The separation of the enantiomers of the compounds of technical toxaphene (CTTs) on heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin (β-TBDM) has been studied by gas chromatography with electron-capture detection (GC-ECD). Enantiomers of eight of the nine CTTs under investigation were separated on this chiral stationary phase. Separations of the enantioners of CTTs have hitherto been achieved ontert-butyldimethylsilylated β-cyclodextrin (β-BSCD). The chiral resolution values and separation factors of the CTTs on β-TBDM have been compared with those obtained on β-BSCD. Although several components coeluted, enantioselective determination of three CTTs was possible in an extract of seal blubber. For each CTT the first-eluting enantiomer was enantioenriched. Enantioselective accumulation of2-endo, 3-exo,5-endo,6-exo,-8,8,9,10-octachlorobornane (B8-1412) in biota has been established for the first time.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467496
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  • 49
    Digitale Medien
    Digitale Medien
    Determination of triacylglycerol composition of idiazabal cheese (1998)
    Springer
    Chromatographia 47 (1998), S. 579-586 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Column liquid chromatography ; Ewe's cheese ; Triacylglycerols
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Triacylglycerols from Idiazabal cheese fat were analysed by high-performance liquid chromatography (LC) with a non-linear gradient of acetone in acetonitrile and a light-scattering detector. Molecular species of triacylglycerols were predicted by a simple and a multiple linear regression analysis of logk of the LC peaks and molecular variables such as equivalent carbon number of the possible triacylglycerol, chain length and number of double bonds of each fatty acid of the triacylglycerol. Predicted results were confirmed by gas chromatographic analysis of the fatty acids in the LC peaks. The main triacylglycerols of Idiazabal cheese fat contained butyric acid, butyroyl-dipalmitin, butyroyl-myristoyl-palmitin and butyroyl-palmitoyl-olein. The most abundant triacylglycerols were those with even partition numbers of 36, 34 and 38.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467499
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  • 50
    Digitale Medien
    Digitale Medien
    Charge-transfer interactions between nucleophilic compounds and chromatographic packings containing chemically bonded Cu(II) complexes (1998)
    Springer
    Chromatographia 48 (1998), S. 284-292 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Metal complexes ; Chemically bonded phases ; Thermodynamic parameters ; Specific interactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Results are presented of studies of packings containing copper (II) acetylacetonate (acac), hexafluoroacetylacetonate (hfac), and chloride, chemically bonded via β-dik-etonate groups. The retention parameters retention factor (k) specific retention volume (V g), and molecular retention index (M e) were measured and used to calculate the thermodynamic parameters free energy of adsorption (ΔG a) heat of adsorption (−ΔH a), and entropy of adsorption (ΔS a). These parameters enable, characterization of specific interactions between aromatic and cyclic hydrocarbons, ethers and thioethers and metal complexes chemically bonded, to a silica surface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467684
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  • 51
    Digitale Medien
    Digitale Medien
    Effects of pargyline and SKF-525A on brain N,N-dimethyltryptamine concentrations and hyperactivity in mice (1981)
    Springer
    Psychopharmacology 75 (1981), S. 179-183 
    Details
    ISSN: 1432-2072
    Schlagwort(e): DMT ; Gas chromatography ; Hyperactivity ; Pargyline ; SKF-525A ; Mice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Mice pretreated with the monoamine oxidase inhibitor pargyline showed a dose-dependent increase in hyperactivity for up to 2 h following injections of N,N-dimethyltryptamine (DMT: 0.5–8.0 mg/kg). Hyperactivity was related to a linear increase in whole brain concentrations of DMT as measured by a new sensitive gas chromatographic assay. The duration of this behaviour paralleled the concentration of DMT in the brain from 15–120 min. However, at 15 min, there was no significant difference in brain DMT concentrations between mice receiving pargyline and those given distilled water at the two dose levels of DMT studied (2.0 and 8.0 mg/kg). Pre-treatment with the microsomal enzyme inhibitor SKF-525A, alone or in combination with pargyline, had no effect on the DMT-induced behaviour or on the brain levels of DMT.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00432184
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  • 52
    Digitale Medien
    Digitale Medien
    Measurement of the urinary metabolites of n-hexane, cyclohexane and their isomers by gas chromatography (1981)
    Springer
    International archives of occupational and environmental health 48 (1981), S. 99-106 
    Details
    ISSN: 1432-1246
    Schlagwort(e): Urine analysis metabolites ; Gas chromatography ; Hexane ; Cyclohexane ; Biological monitoring
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A gas chromatographic method for analyzing the urinary metabolites of n-hexane (2-hexanol, 2,5-hexanedione, 2,5-dimethylfuran and γ-valerolactone), of 2-methylpentane (2-methyl-2-pentanol), of 3-methylpentane (3-methyl-2-pentanol), and of cyclohexane (cyclohexanol) was developed. Processing of urine and the gas chromatographic conditions are described. The recovery rate of all hexane metabolites, except 2,5-dimethylfuran, ranged between 92 and 100%. The variation coefficient of metabolites determination was between 1.5 and 5%, apart from 2,5-dimethylfuran determination for which the variation coefficient was 15%. The detection limits ranged between 0.2 and 0.7 mg/1 and between 0.05 and 0.1 mg/1 when a packed or capillary column was used. Results obtained from a packed and capillary column are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00405936
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  • 53
    Digitale Medien
    Digitale Medien
    Internal standardization in the head space analysis of organic solvents in blood (1981)
    Springer
    International archives of occupational and environmental health 49 (1981), S. 115-123 
    Details
    ISSN: 1432-1246
    Schlagwort(e): Blood analysis of solvents ; Gas chromatography ; Head space ; Toxicokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The determination of toluene, benzene, ethylbenzene and trichloro-ethylene in blood by means of a gas chromatographic head space technique is presented. Internal standards are added to the blood samples in the form of water solutions of volatile hydrocarbons in proportion 2:1. This enables application of the internal standard within the broad range of concentrations and in addition increases significantly the concentrations of investigated compounds in the gas phase of incubation vessel. Elaborated methods were applied for determinations of ethylbenzene in blood samples collected after experimental inhalation exposure and for evaluation of the rate of disappearance of benzene, toluene and trichloro-ethylene from blood after acute accidental or suicidal intoxications.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00377664
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  • 54
    Digitale Medien
    Digitale Medien
    Occupational exposure to hexachlorocyclohexane (1981)
    Springer
    International archives of occupational and environmental health 48 (1981), S. 319-324 
    Details
    ISSN: 1432-1246
    Schlagwort(e): Chlorophenols ; Gas chromatography ; Hexachlorocyclohexane ; Metabolites
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A sensitive and specific gas chromatographic method is described for the simultaneous determination of ten chlorinated phenols that appear in the urine of persons exposed to hexachlorocyclohexane (HCH). The phenolic compounds in the urinary samples are hydrolysed in an acidic medium and derivatised with acetic anhydride. This sample treatment permits routine application. The stationary phase (8% DC 200 on Chromosorb G AW-DMCS possesses a high separating capability for the acetic esters of the chlorophenols. The detection limits lie between 4.9 and 18.6 μg/l and allow determinations even in the environmentally interesting concentration range. The recoveries determined using aqueous standards range between 87 and 119% and the relative standard deviations are between 4.4 and 10.1%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00378679
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  • 55
    Digitale Medien
    Digitale Medien
    3-methoxytyramine: Its suitability as an indicator of synaptic dopamine release (1981)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 315 (1981), S. 219-225 
    Details
    ISSN: 1432-1912
    Schlagwort(e): 3-Methoxytyramine ; Haloperidol ; Dopamine release ; Dopamine agonists ; Gas chromatography ; Mass Spectrometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The value of 3-methoxytyramine (3-MT) as an indicator of impulse-related dopamine (DA) release has been assessed in rat corpus striatum. Moreover, the turnover of 3-MT was estimated by measuring its disappearance rate after COMT inhibition. Quantitation of 3-MT and DA was performed by gas chromatography/mass spectrometry (selected ion monitoring). Haloperidol in doses between 0.05 and 3 mg/kg p.o. did not increase endogenous 3-MT levels at any time up to 24 h after its administration, whereas it dose-dependently increased homovanillic acid and 3,4-dihydroxyphenylacetic acid. However, in doses above 0.1 mg/kg p.o., it enhanced the accumulation of 3-MT in clorgyline-pretreated animals. Conversely, baclofen in doses of 2 mg/kg i.p. and above decreased endogeneous 3-MT levels, but reduced the accumulation of this amine only poorly at 20 mg/kg i.p. in clorgyline-pretreated rats. A number of dopamine agonists, apomorphine (0.5 mg/kg i.v.), dipropyl-ADTN (0.03 mg/kg i.v.), but not bromocriptine (1 mg/kg i.v.) reduced endogenous 3-MT levels 10 min after administration by approximately 50%. The DA releasing agents d-amphetamine and methylphenidate showed different effects: the former increased endogenous 3-MT greatly, whereas the latter was without effect. The difference is likely to be related to the MAO inhibitory properties of amphetamine. 3-MT disappeared rapidly after COMT inhibition with 50 mg/kg i.v. tropolone (half-life of the initial disappearance about 1 min). The curve flattened off after 5–10 min. Turnover was calculated to be about 7 nmol/g/h, which corresponds to about a third of the turnover of DA. Our results suggest that an important part of DA metabolism occurs through 3-MT and that this amine is very effectively deaminated by MAO-A, so effectively indeed that increased formation does not increase its endogeneous levels. It appears, therefore, that 3-MT is not suitable as an indicator of increased DA release. However, it seems to have some value for an assessment of lowered DA release.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00499838
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  • 56
    Digitale Medien
    Digitale Medien
    Chemically modified teflon wall-coated open tubular columns for gas chromatography (1981)
    Springer
    Chromatographia 14 (1981), S. 19-22 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Teflon columns ; Chemically modified teflon ; Gas chromatography ; Capillary columns
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Wall-coated open tubular columns prepared from chemically modified teflon tubing have been developed for gas chromatography. Chemical reaction of the inner walls of teflon tubing allows bonding of an adhesive layer on which a variety of stationary phaes can be coated. Test mixtures of alkanes and alcohols were used to investigate the chromatographic properties of these columns and the stability and mixing of the adhesive and stationary phae layers. the results in dicate that mixing of the layers is negligible and that the column is stable for a long period of time.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262057
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  • 57
    Digitale Medien
    Digitale Medien
    Die Herstellung von Glas-Kapillarsäulen für die Gas-Chromatographie (1981)
    Springer
    Chromatographia 14 (1981), S. 55-66 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Capillary columns, glass ; Gas chromatography ; Column preparation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Kapillar-Gas-Chromatographie ist heute das sich am stärksten entwickelnde Gebiet der Gas-Chromatographie. Es gibt viele komplexe, neue Fragestellungen in der Analytik, welche den Einsatz spezieller Kapillarsäulen erfordem. Glücklicherweise gibt es aber auch eine große Zahl von Herstellungsverfahren für Kapillarsäulen, welche — noch mehr als bei der Herstellung von gepackten Säulen — eine Anpassung an die gestellten Aufgaben ermöglichen. In diesem Artikel werden die Herstellungsverfahren für Kapillarsäulen zusammengestellt und Anregungen gegeben, wie aufgaben-orientierte Säulen erreicht werden.
    Notizen: Summary Glass capillary column chromatography is the most rapidly growing part of gas chromatography. There are many complex new analytical tasks and they require special capillary columns, Fortunately there is a wide range of column preparation methods available, and they make the preparation of glass capillary columns a more varied job than that of packed columns. In this paper these methods are reviewed and suggestions are given for making task-oriented columns.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262064
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  • 58
    Digitale Medien
    Digitale Medien
    Gas chromatographic analysis of phenylurea herbicides following catalytic hydrolysis on silica gel (1981)
    Springer
    Chromatographia 14 (1981), S. 579-586 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Urea herbicides ; Catalytic hydrolysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method is described for the rapid catalytic hydrolysis of phenylurea herbicides on silica gel at elevated temperatures. After derivatisation of the anilines produced with heptafluorobutyric acid anhydride final analysis is done on a gas chromatograph equipped with an electroncapture detector. Detection limits are in the 1–5 picogram range. The method has successfully been applied to residue analysis of water samples at the 1 ppb level. The determination of free anilines present in water samples and the potential of various techniques to be used to discriminate between free anilines and parent herbicides are also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262887
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  • 59
    Digitale Medien
    Digitale Medien
    Gas chromatographic analysis of water phenolic pollutants using acid-washed graphitised carbon black (1981)
    Springer
    Chromatographia 14 (1981), S. 86-88 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Graphitised carbon black ; Phenols ; Water pllutants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The fractionation of eleven phenols which may be contaminants in drinking water has been accomplished by using acid-washed graphitised carbon black modified with trimesic acid and PEG 20 M.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02279517
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  • 60
    Digitale Medien
    Digitale Medien
    Novel applications for headspace gas chromatography (1981)
    Springer
    Chromatographia 14 (1981), S. 447-451 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Headspace analysis ; Gas chromatography ; Residual analysis of polyethylene terephthalate ; Acetylene reduction assay ; Ethylene evolution in germinating seed ; Acetaldehyde generation in polyester resin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary New application areas for headspace gas chromatography in agricultural and polymer degradation research are described. Specific examples are drawn from the various forms of headspace analysis with emphasis on the automated static equilibrium method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02263531
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  • 61
    Digitale Medien
    Digitale Medien
    Bausteine von Oligosacchariden, XXIX. Synthese des Trisaccharids aus N-Acetylglucosamin, Galactose und Rhamnose einer O-determinanten Kette von Escherichia Coli (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3079-3101 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Building units for Oligosaccharides, XXIX. Synthesis of a Trisaccharide Chain of N-Acetylglucosamine, Galactose and Rhamnose of an O-Determinant from Escherichia coli. Dependence of Stereoselectivity of the α-Glycoside Synthesis on the Reactivity of the PyranosylhalideThe mercury salt catalysed reaction of substituted α-D-galactosyl halides with the reactive 4-OH groups of the rhamnosides 18 and 19 were studied. The order of reactivity of the halides increases with the following substituents: O-acetyl 〈 O-glucosyl 〈 O-benzyl. The order of selectivity, towards the α-glycoside, was the reverse. The selectivity can be improved by either decreasing the reactivity of the glycosyl halide, in the case of highly reactive hydroxyl groups, or by decreasing the nucleophilicity of the hydroxyl groups, in the case of highly reactive halides. Various trisaccharides, like 58 which represents the repeating-unit of the lipopolysaccharide from Escherichia coli O 75, were synthesized from N-acetylglucosamine, galactose and rhamnose.
    Notizen: Die Quecksilbersalz-katalysierte α-Glycosidsynthese von gemischt substituierten α-D-Galactosylhalogeniden mit den reaktiven 4-OH-Gruppen der Rhamnoside 18 und 19 wird untersucht. Die Reaktivität der Halogenide nimmt bei Anwesenheit der folgenden Substituenten zu: O-Acetyl 〈 O-Glycosyl 〈 O-Benzyl. Parallel dazu nehmen die Selektivität und der Anteil and α-Glycosid ab. Notwendige Selektivitätsverbesserungen können bei zu reaktiven OH-Gruppen durch Verminderung der Reaktivität des Glycosylhalogenids, bei zu reaktiven Glycosylhalogeniden durch Verminderung der Reaktivität der OH-Gruppe erzielt werden. Verschiedene Trisaccharideinheiten aus N-Acetylglucosamin, Galactose und Rhamnose werden synthetisiert, wobei 58 einer Teil-struktur der repeating-unit der O-Determinante des Lipopolysaccharids aus Escherichia coli O 75 entspricht.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811140915
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  • 62
    Digitale Medien
    Digitale Medien
    Bausteine von Oligosacchariden, XXXI. Synthese der Repeating-Unit der O-spezifischen Kette des Lipopolysaccharides des Bakteriums Escherichia coli O 75 (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3115-3125 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Building Units for Oligosaccharides, XXXI. Synthesis of the Repeating-Unit of the O-Specific Chain of the Lipopolysaccharide from Escherichia coli O 75Reaction of the trisaccharidehalide-block 12 with the benzyl rhamnoside 13 gave a tetrasaccharide which, after complete removal of the protecting groups, yielded the branched tetrasaccharid 1 (see german summary). This represents the repeating-unit of the O-specific chain of the lipopolysaccharide from Escherichia coli O 75. A simular reaction between the block 12 and the 8-ethoxycarbonyloctyl rhamnoside 19 leads to the tetrasaccharide 20 which contains a suitable spacer-unit for coupling with a protein to give a synthetic antigen.
    Notizen: Durch eine Synthese, bei der der Trisaccharidhalogenid-Block 12 verwendet wird, läßt sich nach vollständiger Entblockierung das verzweigte Tetrasaccharid erhalten, das die repeating-unit der O-spezifischen Kette des Bakteriums Escherichia coli O 75 darstellt. Durch Verknüpfung des Blocks 12 mit dem Rhamnosid 19, einem Glycosid des 8-Ethoxycarbonyloctanols, wurde das spacer-haltige Tetrasaccharid 20 synthetisiert. Dieses ist ein Hapten, das zur Anknüpfung an ein Protein und somit zur Gewinnung eines synthetischen Antigens geeignet ist.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811140917
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  • 63
    Digitale Medien
    Digitale Medien
    Substituierte einkernige Carbonyleisendihydride (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3549-3557 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Substituted Mononucleus Carbonyliron HydridesSubstitution of H2Fe(CO)4 by ligands like L = As(C6H5)3, Sb(C6H5)3 and P(OC6H5)3 in 1:1 ratio leads to fac monosubstituted compounds H2Fe(CO)3L. A 1:2 ratio results in the isolation of disubstituted complexes H2Fe(CO)2L2, L = P(OCH2)3CC2H5, P(OC6H5)3. The structure of H2Fe(CO)3As(C6H5)3 Was elucidated by X-ray analysis.
    Notizen: Substitution von H2Fe(CO)4 mit Liganden L = As(C6H5)3, Sb(C6H5)3 und P(OC6H5)3 im Molverhältnis 1:1 Führt zu fac-Monosubstitutionsverbindungen H2Fe(CO)3L. Im Verhältnis 1:2 können trans-Disubstitutionskomplexe H2Fe(CO)2L2, L = P(OCH2)3CC2H5, P(OC6H5)3, erhalten werden. Von H2Fe(CO)3As(C6H5)3 wurde eine Röntgenstrukturanalyse ausgeführt.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141108
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  • 64
    Digitale Medien
    Digitale Medien
    Reaktivität des Silaethens Me2Si=C(SiMe3)2: Thermolyse von (Me3Si)2(Me2XSi)CLi (X z. B. (PhO)2PO2) in Anwesenheit von Silaethen-Fängern (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3518-3532 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Reactivity of the Silaethene Me2Si=C(SiMe3)2: Thermolysis of (Me3Si)2(Me2XSi)CLi (X e. g. (PhO)2PO2) in the Presence of Silaethene Trapping ReagentsSilaethene Me2Si=C(SiMe32 (1), generated as a reaction intermediate by the thermal elimination of LiX from Me2XSi—CLi(SiMe3)2, combines with the reactants a-b (e. g. Me3Si—Cl, Me3Si—OMe) with insertion in the a-b bond, with a = b-c-H (e. g. CH2=CMe—CH2—H) under ene-reaction and with (e. g. CH2=CR—CR=CH2, O=N=N, Ph2C=NSiMe3, Me3SiN=NSiMe3, PhC=N) under [2 +4]-, [2 + 3]- [2 + 2]- as well as [2 + 2 + 2]-Cycloaddition. Some of the cycloadducts, so obtained, are thermolabile and decompose under cycloreversion, which may lead to the formation of 1 and also to Me2Si=NSiMe3. The following order of relative reactivity of 1-trapping reagents has been found (formation of 1 at -10°C): Me3Si—NMe2 Me3Si—Cl 〈 PhC≡N 〈 1,3-butadien 〈 2.3-Dimethyl-1,3-butadien ≍ isobuten 〈 Me3Si—OMe 〈 Ph2C=NSiMe3 〈 PhN=NPh 〈 Me3SiN=NSin=NSiMe3 ≪ Ph2C=O, Me3SiN=N=N.
    Notizen: Das durch thermische LiX-Eliminierung aus Me2XSi—CLi(SiMe3)2 als Reaktionszwischenstufe erzeugbare Silaethen Me2Si=C(SiMe3)2 (1) reagiert mit Reaktanden a-b (z. B. Me3Si—Cl, Me3Si-OMe) unter Insertion in die a-b-Bindung, mit a = b-c-H (z. B. CH2 CMe—CH2—H) unter En-Reaktion und mit (z. B. CH2=CR—CR=CH2, O=N=N, Ph2C=NSiMe3, Me3SiN=NSiMe3, PhC≡N) unter [2 +4]-, [2+3]-[2 + 2]- sowie [2 + 2 + 2]-Cycloaddition ab. Die erhaltenen Cycloaddukte sind zum Teil thermolabil und zerfallen unter Cycloreversion u. a. unter Bildung von 1 sowie auch Me2Si=NSiMe3. Folgende Reihe relativer Reaktivitäten von 1-Fängern wurde gefunden (Erzeugung von 1 bei -10°C): Me3Si—NMe2 Me3Si—Cl 〈 PhC≡N 〈 1,3-Butadien 〈 2,3-Dimethyl-1,3-butadien ≍ Isobuten 〈 Me3Si—OMe 〈 Ph2C=NSiMe3 〈 PhN=NPh 〈 Me3SiN=NSiMe3 ≪ Ph2C=O, Me3Sin=N=N.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141106
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  • 65
    Digitale Medien
    Digitale Medien
    Aliphatische Azoverbindungen, XIII: cis- und trans-1-Azonorbornan (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3533-3548 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Aliphatic Azo Compounds, XIII: cis- and trans-1-AzonorbornaneThe rates of isomerisation of cis-1-azonorbornane to the trans-isomer at 96.6°C in a series of aprotic solvents follow a linear correalation with ET30. The small slope of the correlation -0.034 argues for isomerisation via semilinearisation in agreement with theory. In protic solvents the isomerisation proceeds faster possibly due to a faster isomerisation by bond rotation which could be favoured by H-bonding. The heat and the activation parameters of the isomerisation and the activation parameters of thermal decomposition of trans-1-azonorbornane allow the construction of a complete enthalpy diagram of this system. The structure of cis-1-azonorbornane was determined by X-ray analysis at -60°C. The observed angle deformations and the normal NN-bond lengths are reproduced by force field calculations.
    Notizen: Die Isomerisierungsgeschwindigkeit von cis- in trans-1-Azonorbornan (1) folgt bei 96.6°C linear dem Polaritätsparameter ET30 in verschiedenen aprotischen Lösungsmitteln. Die geringe Steigung -0.034 dieser Korrelation deutet auf einen theoretisch vorgeschlagenen einfachen Inversionsmechanismus. In protischen Lösungsmitteln verläuft die Isomerisierung viel schneller, wofür ein durch H-Drücken begünstigter Rotationsmechanismus Möglich gehalten wird. Reaktionsenthalpie und Aktivierungsparameter der cis-trans-Isomerisierung und die Aktivierungsparameter der Thermolyse von trans-1-Azonorbornan gestatten die Aufstellung eines vollständigen Enthalpiediagramms. Die Struktur von cis-1 wurde durch Röntgenanalyse bei -60°C bestimmt. Die starke Winkeldeformation und der normale NN-Abstand im Kristall werden durch Kraftfeldrechnungen richtig wiedergegeben.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141107
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  • 66
    Digitale Medien
    Digitale Medien
    Metallcarbonyl-Synthesen, X: Synthese neuer Niob- und Tantal-Halbsandwichkomplexe. Molekülstruktur der Stammverbindung (η5-C5H5)Nb(CO)4 (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3558-3571 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Metalcarbonyl Syntheses, X: Synthesis of New Niobium and Tantalum Halfsandwich Complexes. Molecular Structure of the Parent Compound (η5-C5H5)Nb(CO)4The halfsandwich complexes (η5-C5H4CH3)Nb(CO)4 (3a), [η5-C5(CH3)5]Nb(CO)4 (3b), (η5-C5H4CH3)Ta(CO)4 (3c), and [η5-C5(CH3)5]Ta(CO)4 (3d) are accessible by reductive high-pressure carbonylation of the corresponding NbV- and TaV precursors (η5-C5R4R′)MCl4 (2a-d). Successive introduction of methyl groups in the cyclopentadienyl ring facilitates the reduction of the halogeno complexes 2a-d; moreover, the niobium complexes are more susceptible to reduction than their tantalum counterparts. Upon photolysis of the carbonyl complexes 3a-d in tetrahydrofuran, the solvens complexes of type (η5-C5R4R′)M(CO)3(THF) (4a-d) are generated. The parent compound (η5-C5H5)Nb(CO)4 (1) has a regular square-pyramidal structure as shown by X-ray analysis.
    Notizen: Die Halbsandwich-Komplexe (η-5C5H4CH3)Nb(CO)4 (3a), [η5-C5(CH3)5]Nb(CO)4 (3b), (η5-C5H4CH3)Ta(CO)4 (3c) und [η5-C5(CH3)5]Ta(CO)4 (3d) sind durch reduzierende Hochdruckcarbonylierung der entsprechenden NbV-bzw. TaV-vorstufen (η5-C5R4R′)MCl4 (2a-d) synthetisierbar. Die Reduzierbarkeit der Halogeno-Komplexe, 2a-d, wird durch sukzessive Einführung von Methyl-Substituenten in den Cyclopentadienyl-Ring erleichtert und ist bei den Niob-Verbindungen mit milderen Reduktionsmitteln als bei den analogen Tantal-Komplexen möglich. Bei der Photolyse von 3a-d in Tetrahydrofuran entstehen die Solvens-Komplexe (η5-C5R4R′)M(CO)3(THF) (4a-d). Die Stammsubstanz (η5-C5H5)Nb(CO)4 (1) wurde röntgenstrukturanalytisch untersucht und besitzt eine unverzerrt tetragonal-pyramidale Molekülstruktur.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141109
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  • 67
    Digitale Medien
    Digitale Medien
    Komplexe von Germanium(II)-chlorid mit 1,2-Bis(diphenylphosphino)ethan: Ein Halb-Chelat und ein Doppel-Ylid (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3572-3580 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Complexes of Germanium Dichloride with 1,2-Bis(diphenylphosphino)ethane: A Semi-Chelate and A Double-Ylide1,2-Bis(diphenylphosphino)ethane (dppe) reacts with the germanium dichloride dioxane complex depending on the stoichiometric ratio to give a 1:2 dppe-bridged bis(germylene) complex (1) or a 1:1 complex (2) that shows equilibration of both phosphorus atoms in 31P-NMR. The crystal structure of 2 has been determined from single crystal X-ray data. The compound crystallizes with 8 units dppe-GeCl2· 1/2 C6H6 in a unit cell of symmetry A 2/a-C2h6 in a monoclinic system. The dppe-GeCl2 molecules contain a novel semi-chelating type of coordination of the dppe ligand [distorted Ψ-trigonal bipyramidal coordination at Ge11 with an exceptionally long distance Ge-P(apical)]. 2 thus represents an intermediate structure between chelate complex and phosphorus ylid.
    Notizen: 1,2-Bis(diphenylphosphino)ethan (dppe) reagiert mit dem Germanium(II)-chlorid-Dioxankomplex je nach Mengenverhältnis zu einem dppe-verbrückten Bis(germylen)-Komplex (1) oder zu einem 1:1-Komplex (2), der sich durch die Äquivalenz der Phosphanfunktionen in Lösung (31PNMR) auszeichnet. 2 kristallisiert mit 1/2 C6H6 monoklin mit acht Einheiten der Formal dppe-GeCl2· 1/2 C6H6 in der Elementarzelle, Raumgruppe A 2/a-C2h6. Die verzerrt Ψ-trigonal-bipyramidale Koordination um Ge11 mit ungewöhnlich langem Abstand Ge-p(apikal) weist 2 als Komplex mit halb-chelierendem dppe-Liganden aus (Zwischenstellung zwischen Chelatkomplex und einfachem \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm P}\limits^{\rm + } - \mathop {{\rm Ge}}\limits^{\rm - } - {\rm Ylid} $\end{document}).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141110
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  • 68
    Digitale Medien
    Digitale Medien
    Autoxidation von Trialkylboranen, II: 1H-NMR-Spektroskopische Untersuchungen zum Mechanismus der Redoxreaktion zwischen Trialkylboranen und Dialkyl(alkylperoxy)boranen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3581-3588 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Autoxidation of Trialkylboranes, II: 1H NMR Spectroscopic Investigations on the Mechanism of the Redox Reaction between Trialkylboranes und Dialkyl(alkylperoxy)boranesThe intermolecular redox reaction between dimethyl(methylperoxy)borane and [D9]trimethylborane, triethylborane, tri-n-propylborane, triisopropylborane, and tri-n-butylborane, as well as between [D9]dimethyl(methylperoxy)borane and trimethylborane was investigated directly in an NMR spectrometer. From the CIDNP effects a mechanism of this redox reaction was deduced, which can be considered as generally valid for any reaction between (alkylperoxy)boranes and alkylboranes. According to this mechanism, the alkoxy group of the peroxide is transferred to the boron atom of the alkylborane after homolysis of the O—O bond. The four-coordinate boron compound eliminates instantly an alkyl radical, which forms a radical pair in the singlet state with the boroxyle radical left after the homolysis of the peroxide.
    Notizen: Die intermolekularen Redoxreaktionen Zwischen Dimethyl(methylperoxy)boran und [D9]Trimethylboran, Triethylboran, Tri-n-propylboran, Triisopropylboran und Tri-n-butylboran sowie zwischen [D9]Dimethyl(methylperoxy)boran und Trimethylboran wurden in Lösung im 1H-NMR-Spektrometer untersucht. Aus den CIDNP-Effekten wird ein allgemeingültiger Mechanismus der Redoxreaktion zwischen (Alkylperoxy)boranen und Alkylboranen abgeleitet. Danach wird in einem Stoßkomplex zwischen (Alkylperoxy)boranen und Alkylboran durch Homolyse der O—O-Bindung gezielt die Alkoxygruppe des Peroxids auf das Boratom des Alkylborans übertragen. Das vierfach koordinierte Alkoxyalkylboran stößt sofort ein Alkyl-Radikal ab, welches mit dem Boroxylradikal aus der Spaltung des Peroxids zu einem Radikalpaar mit Singulett-Konfiguration der Radikalelektronen zusammenfindet.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141111
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  • 69
    Digitale Medien
    Digitale Medien
    Hochfluorierte Phosphor-Ylide und Phosphoniumsalze (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3589-3598 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Highly Fluorinated Phosphorus Ylides and Phosphonium SaltsThe (perfluoroalkyl)iodophosphanes n-C6F13PI2 and (n-C6F13)2PI, obtained from n-C6F13I and white phosphorus at 235°C under pressure, are converted into the chlorides n-C6F13PCI2 and (n-C6F13)2PCl with HgCl2. The chlorides are methylated with LiCH3 to form the methylphosphanes n-C6F13P(CH3)2, (6) and CH3P(n-C6F13)2 (5), respectively. Only 6, but not 5, can be quaternized with CH3I to yield a phosphonium salt, [n-C6F13P(CH3)3]I (8). In reactions of 8 with strong bases no corresponding ylide is generated, but a phosphorane n-C6F13P(CH3)4 is obtained instead. More highly fluorinated phosphonium salts could not be prepared. - The Phosphanes (CH3)2PC6F5 (11) and CH3P(C6F5)2 (12) yield onium salts [(CH3)3PC6F5]X (13) and [(CH3)2P(C6F5)2]X (14), resp., when treated with methylating agents. P(C6F5)3 undergoes dearylation reactions under comparable conditions. 13 and 14 are transformed into dark red unstable ylides, which oligomerize with autocondensation and could not be identified. From 12 and C6F5CH2Br a red ylide 17 is obtained, via the onium salt 16, which can be isolated and characterized by spectroscopic data. Stable yellow ylides R3P=CHC6F5 (19a-c, R = CH3, i-C3H7, C6H5) are generated similarly from the phosphonium salts [R3PCH2C6F5]Br. Reduction of the carbanion nucleophilicity by the C6F5 groups appears to prevent autocondensation in these cases.
    Notizen: Die aus weißem Phosphor und n-C6F13I bei 235°C unter Druck dargestellten (Perfluoralkyl)iodphosphane n-C6F13PI2 und (n-C6F13)2PI werden mit HgCl2 in die Chloride n-C6F13PCl2 and (n-C6F13)2PCl umgewandelt und diese mit LiCH3 in die Methylphosphane n-C6F13P(CH3)2 (6) und CH3P(n-C6F13)2 (5) übergeführt. Von diesen ist nur 6 mit CH3I quartärisierbar. Das entstehende Salz [n-C6F13P(CH)3)3]I (8) ergibt mit starken Basen nicht das korrespondierende Ylid, sondern das Phosphoran n-C6F13P(CH3)4 (10). Höher fluorierte Phosphoniumsalze sind nicht zugänglich. - Die Phosphane (CH3)2PC6F5 (11) und CH3P(C6F5)2 (12) ergeben mit Methylierungsmitteln noch die Oniumsalze [(CH3)3PC6F5]X (13)bzw. [(CH3)2P(C6F5)2]X (14). P(C6F5)3 erleidet dagegen unter vergleichbaren Bedingungen eine Entarylierung. 13 und 14 werden von starken Basen in tief rote instabile Ylide übergeführt, die durch Autokondensation oligomerisieren und nicht faßbar sind. Mit C6F5CH2Br entsteht aber aus 12 über das Oniumsalz 16 ein rotes Ylid 17, das isoliert und spektroskopisch charakterisiert werden kann. Analog ergeben sich aus Salzen [R3PCH2C6F5]Br stabile gelbe Ylide R3P=CHC6F5 (19a-c, R = CH3, i-C3H7 und C6H5). Die Verminderung der Carbanion-Nucleophilie dieser Ylide durch die C6F5-Gruppe verhindert die Autokondensation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141112
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  • 70
    Digitale Medien
    Digitale Medien
    Oxidative Additionen an 2-Amino-4,4,5,5-tetrakis(trifluormethyl)-1,3,2-dioxaphospholan (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3609-3624 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Oxidative Additions to 2-Amino-4,4,5,5-tetrakis(trifluoromethyl)-1,3,2-dioxaphospholaneOxidative addition of HF, Cl2 and (CF3)2CO to the title compound 6 furnishes the phosphoranes 2, 9, and 3, respectively. In the case of NH4[OC(CF3)C(CF3)2OH] (4) the hydrospirophosphorane 1 is obtained via a substitution reaction followed by an oxidative addition. Compound 9 is a precursor for the aminotetraalkoxyphosphoranes 5, 8, and the very stable phosphazene 10 which is formed by loss of HCl by thermolysis. Due to a slow ligand exchange the 19F NMR spectrum of phosphorane 3 exhibits eight magnetically non equivalent CF3 groups. By means of 19F homodecoupling experiments extensive through space coupling is found in the molecule. The x-ray structure analysis of 3 shows a slight distortion from the trigonal bipyramidal geometry at phosphorus. For comparison, F2PNH2 and tBu2PNH2 react with (CF3)2 to form (CF3)2C=NH, the aminofluorophosphorane 11, F2P(=O)OCH(CF3)2 (13) bzw. von tBu2P(=o) (12) and tBu2P(=O)OCH(CF3)2 (14), respectively.
    Notizen: Durch oxidative Addition von HF, Cl2 und (CF3)2CO and die Titelverbindung 6 entstehen die Phosphorane 2, 9 und 3; mit NH4[OC(CF3)2C(CF3)2OH] (4) wird unter Abspaltung von NH3 und oxidativer Addition das Hydrophosphoran 1 erhalten. Durch Substitution von Chlor lassen sich aus 9 die Aminoalkoxyphosphorane 5 und 8 synthetisieren, während die Thermolyse unter HCl-Abspaltung zu dem äußerst beständigen Phosphazen 10 führt. Verbindung 3 zeigt im 19F-NMR-Spektrum wegen eingeschränkter dynamischer Prozesse acht magnetisch nicht äquivalente CF3-Gruppen. Durch 19F-Homoentkopplungsexperimente werden weitreichende Raumkopplungen nachgewiesen. Die Röntgenstrukturanalyse von 3 ergibt eine annähernd trigonal-bipyramidale Koordination des Phosphors, F2PNH2 und tBu2PNH2, zur vergleichenden Betrachtung herangezogen, reagieren mit Hexafluoraceton unter Bildung von (CF3)2C=NH sowie des Amino-fluorphosphorans 11 und des Phosphorsäureesters F2P(=O)OCH(CF3)2 (13) bzw. von tBu2P(=O)H (12) und tBu2P(=O)OCH(CF3)2 (14).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141114
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  • 71
    Digitale Medien
    Digitale Medien
    Au55[P(C6H5)3]12CI6  -  ein Goldcluster ungewöhnlicher Größe (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3634-3642 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Au55[P(C6H5)3]12Cl6- a Gold Cluster of an Exceptional sizeThe reduction of (C6H5)3PAuCl with B2H6 in benzene yields Au9,2[P(C6H5)3]2Cl which is characterized by means of molecular weight determinations as Au55[P(C6H5)3]12Cl6. A simple model, based on an arrangement of close-packed gold atoms, leads to a gold cluster the structure of which is in good agreement with the unusual chemical composition. The Mößbauer spectrum of the compound shows four different kinds of gold atoms: a metallic part (Au13-nucleus), Au atoms coordinated by P(C6H5)3 and Cl ligands, resp., as well as uncoordinated surface gold. The complex can be decomposed by bromine and iodine to (C6H5)3PAuCl, (C6H5)3PAuBr(I), and metallic gold. The thermolysis at 50°C leads to [(C6H5)3P]2AuCl and gold quantitatively.
    Notizen: Die Reduktion von C6H5)3PAuCl mit B2H6 in Benzol ergibt Au9,2[P(C6H5)3]2Cl, das mittels Molmassebestimmungen als Au55[P(C6H5)3]12Cl6 charakterisiert wurde. Ein einfaches Modell, beruhend auf einer Anordnung dichtest gepackter Goldatome, führt zu einem Goldcluster, dessen Aufbau mit der ungewöhnlichen chemischen Zusammensetzung in guter Übereinstimmung ist. Das Mößbauer-Spektrum der Verbindung zeigt vier Sorten von Goldatomen: einen metallischen Anteil (Au13-Kern), durch P(C6H5)3-bzw. Cl-Liganden Koordinierte Au-Atome, sowie unkoordi-niertes Oberflächengold. Mit Brom und lod läß sich der Komplex zu (C6H5)3PAuCl, (C6H5)3 PAuBr(I) und metallischem Gold abbauen. Die Thermolyse bei 50°C führt quantitativ zu [(C6H5)3P]2AuCl und Gold.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141116
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  • 72
    Digitale Medien
    Digitale Medien
    Cyanamidiumsalze: Bildung und Bau (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3655-3666 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Cyanamidium Salts: Their Formation and Molecular StructureThe hexachloroantimonate 6a, is prepared by methylation of di-tert-butylcarbodiimide. According to an X-ray analysis, 6a is not a carbodiimidium salt 1) but a cyanamidium salt with C2ν symmetry of the molecular frame. the cyanamidium salts 6a - j, are prepared either by alkylation of carbodiimides1) or by alkylation of disubstituted cyanamides. Trisubstituted ureas or their thio analogues are not suitable starting materials for the preparation of compounds 6. Reactions of the cyanamidium salts 6 with HCl, water, and diethylamine are described.
    Notizen: Das durch Methylierung von Di-tert-butylcarbodiimid erhältliche Hexachloroantimonate 6a liegt nach einer Röntgenstrukturanalyse nicht als Carbodiimidium-1), sondern als Cyanamidiumsalz mit C2ν-Symmetrie des Molekülgerüstes vor. Die Cyanamidiumsalze 6a - j werden außer durch Alkylierung von Carbodiimiden 1) auch durch Alkylierung von disubstituierten Cyanamiden erhalten. Trisubstituierte Harnstoffe oder Thioharnstoffe sind keine geeigneten Ausgangsverbindungen zur Darstellung der salze 6. Es werden Umsetzungen der cyanamidiumsalze 6 mit HCl, Wasser und Diethylamin beschrieben.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141118
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  • 73
    Digitale Medien
    Digitale Medien
    Übergangsmetallaktivierte organische Verbindungen, X: Synthese und Eigenschaften von all-α-Poly(N-methylpyrrolen) (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3674-3683 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Transition metal Activated Organic compounds, X: Synthesis and Properties of all-α-Poly(N-methylpyrroles)all-α-Poly(N-methylpyrroles) with 2 - 6, 8 and 16 pyrrole units (2 - 8) were synthesized by lithiation of N-methylpyrrole, subsequent reaction with transition metal halides (best yields with NiCl2 as a rule) and repetitions of these processes. These compounds are surprisingly sensitive to heat and light.
    Notizen: all-α-Poly(N-methylpyrrole) mit 2 - 6, 8 und 16 Pyrroleinheiten (2 - 8) wurden durch Lithiierung von N-Methylpyrrol, Umsetzung mit Übergangsmetallhalogeniden (beste Ausbeute meist mit NiCl2) und Wiederholungen dieser Prozesse synthetisiert. Diese Verbindungen sind überraschend empfindlich gegen Hitze und Licht.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141120
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  • 74
    Digitale Medien
    Digitale Medien
    Übergangsmetallaktivierte organische Verbindungen, IX: Synthese von Polyfuranen durch metallorganische oxidative Kupplung (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3667-3673 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Transition Metal Activated Organic Compounds, IX: Synthesis of Polyfurans by Organometallic Oxidative Coupling2,2′- (2a) and 3,3′-bifuran (3), hitherto only accessible by ring-forming syntheses in small yields, and the unknown compounds all-α-terfuran (2b) and all-α-quaterfuran (2c) have been prepared by convenient ring-Connecting syntheses in 85, 46, 16, or 53% yield, respectively. Lithiation of 2a and subsequent reacting with iodine afforded 5-iodo-2,2′-bifuran (6b, 46%). According to competition experiments acidity against n-butyllithium is increasing in the sequence furan 〈 2a, 〈 2b.
    Notizen: 2,2′ - (2a) und 3,3′-Bifuran (3), bisher nur durch ringbildende mehrstufige Synthesen in geringer Ausbeute zugänglich, sowie die noch nicht beschriebenen Verbindungen all-α-Terfuran (2b) und all-α-Quaterfuran (2c wurden durch leicht durchführbare ringverknüpfende Synthesen in 85, 46, 16 bzw. 53proz. Ausbeute erhalten. Lithiierung von 2a und Umsetzung mit Iod führte zu 5-Iod-2,2′-bifuran (6b. 46%). Durch Konkurrenzversuche wurde ansteigende Acidität gegen n-Butyllithium in der Reihe Furan 〈 2a 〈 2b festgestellt.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141119
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  • 75
    Digitale Medien
    Digitale Medien
    Metallhydrazide, XIX: Addition bis(diethylaluminio)substituierter Amidrazone und Carbohydrazide an Nitrile (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3684-3690 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Metal Hydrazides, XIX: Addition of Bis(diethylaluminio)-substituted Amidrazones and Carbohydrazides to NitrilesAmidrazones and carbohydrazides react with two equivalents of triethylaluminium to give bis (diethylaluminio) derivatives 1 and 7, respectively. In contrast to the corresponding mono(diethylaluminio)derivatives or disodium salts, these are capable of addition to nitriles with formation of N1-(aminomethylene)amidrazones(4; 81 - 95%) or N1-acylamidrazones (8 and 9; 56 - 85%), respectively.
    Notizen: Amidrazone und Carbohydrazide reagieren mit zwei Äquivalenten Triethylaluminium zu Bis(diethylaluminio)-Derivaten 1 bzw. 7, die sich anders als die entsprechenden Mono(diethylaluminio)-Derivate oder Dinatriumsalze glatt an Nitrile addieren. Man erhält N1-(Aminomethylen)amidrazone (4; 81 - 95%) bzw. N1-Acylamidrazone (8 und 9; 56 - 85%).
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141121
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  • 76
    Digitale Medien
    Digitale Medien
    Über die Bildung von Trichlorosulfonium (IV)-hexafluoro-arsenat(V) (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3737-3739 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The Formation of Trichlorosulfonium (IV) Hexafluoroarsenate(V)Sulfur reacts with chlorine and arsenic Trifluoride under pressure to give [SCl3]+[AsF6]-. As an intermediate oxidizing substance [AsCI4]+ is identified by spectroscopy. Depolarization-Raman-spectra confirm the assignment made in literature.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141125
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  • 77
    Digitale Medien
    Digitale Medien
    Additionen von Carbonsäure-Dianionen an α, β-ungesättigte Carbonylverbindungen - Steuerung der 1,2-/1,4-Regioselektivität durch sterische Substituenteneffekte (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3701-3724 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Additions of Carboxylic Acid Dianions to α,β-Unsaturated Carbonyl Compounds - Control of the 1,2-/1,4-Regioselectivity by Steric substituent EffectsDilithium carboxylic acid dianions 1 attack α,β-unsaturated aldehydes (2) 1,2-regiospecifically with formation of the unsaturated β-hydroxy carboxylic acids 3/4. Additionally, the addition of the phenylacetate dianion 1a can be conducted to the threo-isomer with high selectivity by reversible reaction. - α,β-Enones (8) add 1 irreversibly in 1,2- and 1,4-position. Depending on the substitution pattern, the whole range from pure 1,2- to pure 1,4-adduct is covered. The influence of the 1-counterion M and of the solvent is significant; the 1,4-portion increases with the complexing effect of M and with the Lewis-basicity of the solvent.
    Notizen: Dilithiumcarbonsäure-Dianionen 1 addieren sich an α,β-ungesättigte Aldehyde (2) 1,2-regiospezifisch unter Bildung der γ,δ-ungesättigten β-Hydroxycarbonsäuren 3/4, wobei im falle des Phenylessigsäure-Dianions (1a)die Addition durch reversible Reaktionsführung zu hoher threo -Selektivität gesteuert werden kann. - α,β-Enone (8) nehmen 1 irreversibel in 1,2- und 1,4-Position auf, wobei nach Maßgabe der Substituenten das gesamte Spektrum von reinem 1,2- zu reinem 1,4-Addukt überstrichen wird. Bei gleichbleibendem Substitutionsmuster steigt der 1,4-Anteil mit der komplexierenden Wirkung der Gegenionen von 1 und mit der Lewis-Basizität des Solvens.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141123
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  • 78
    Digitale Medien
    Digitale Medien
    Synthese mittlerer und großer Ringe, II: Funktionalisierte Cyclodecene und Cyclodecadiene durch Ringerweiterung des Cyclooctins (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3725-3736 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Synthesis of Medium and Large Rings, II: Cyclodecenes and Cyclodecadienes with Functional Groups by Ring Expansion of CyclooctyneThe Diels-Alder adduct 1 from cyclooctyne and diethyl 3,4-furandicarboxylate gives by photolysis and subseqent thermolysis of the resulting oxaquadricyclane 2 the β,β′-bridged hexano-oxepin 3. Oxidative cleavage of one C=C double bond of 3 leads to the monocyclic cyclodecenone derivative 5 which can be converted to cyclodecadienes of the type 6 with an anellated butenolide ring. 6a - c, are chiral butadiene derivatives. 6a can be cleaved with acid or base to give the cyclodecenone 7 or the dicarboxylic acid 8.
    Notizen: Das Diels-Alder-Addukt 1 aus cyclooctin und 3,4-Furandicarbonsäure-diethylester liefert durch Photolyse und anschließende Thermolyse des Oxaquadricyclans 2 das β,β′-überbrückte hexanooxepin 3. Die oxidative Spaltung einer C=C-Doppelbindung von3 führt zum monocyclischen cyclodecenon 5, das sich zu Cyclodecadienen des Typs 6 mit anelliertem Butenolidring abwandeln läßt. 6a - c enthalten eine chirale Butadien-Struktur. Durch Keton- bzw. Säurespaltung von 6a erhält man das Cyclodecenon 7 bzw. die Dicarbonsäure 8. Mögliche Anwendungen des Verfahrens, das die Einführung von funktionellen Gruppen an vier benachbarten C-Atomen des Zehnringes erlaubt, werden besprochen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141124
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  • 79
    Digitale Medien
    Digitale Medien
    Lineare Oligophosphaalkane, III: Synthese und Stereochemie von Palladium(II)-Komplexen chiraler Tetraphosphaalkane H2-nRnP—[CH2]3 — PR′ — m[CH2]m — PR′ — [CH2]3 — PRnH2-n(R, R′, = Me, tBu; m = 2, 3; n = 1, 2) (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3691-3700 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Linear Oligophosphaalkanes, III: Syntheses and stereochemistry of Palladium (II) Complexes of chiral Tetraphosphaalkanes H2-nRnP—[CH2]3 — PR′ — [CH2]m — PR′ — [CH2]3 — PRnH2-n(R, R′, = Me, tBu; m = 2, 3; n = 1, 2)The reaction of the chiral tetradentate ligands L of the title with K2PdCl4 affords the complexes Pd(L)Cl2 (2a - e), which for n = 1 may exist as ten (square pyramidal) or six (square planar coordination geometry) isomers. By suitable choice of the substituents R and size of the chelate rings (m + 3) the number of isomers may be reduced to two or three. The detailed investigation of the complexes 2a - e by means of 31P{1H} NMR spectroscopy offers the possibility to identify their stereochemistry. - Monodeprotonation of 2a (R = Me; m = 3; n = 1) and 2d (R = Me; m = 2; n = 1) by KOH or the OH- Form of anion exchange resin yields the phosphido complexes 3a and d (not isolated). Both compounds are oxidized by air with formation of the phosphanoxidophosphane complexes 4a and d, which exist as two or three configurational isomers with units Pd—P(O)Me—.
    Notizen: Die Umsetzung der im Titel genannten vierzähnigen Liganden L mit k2PdCl4 liefert die Komplexe Pd(L)Cl2(2a-e)w, die für n = 1 in Form von zehn (quadratisch pyramidale Ligandenanordnung) bzw. sechs (planare Koordinationsgeometrie) Konfigurationsisomeren vorliegen können. Durch geeignete Wahl der substituenten R und der Chelatringgröße (m + 3) läßt sich die Zahl der Isomeren auf zwei bzw. drei reduzieren. Die detaillierte 31P{1H}-NMR-spektroskopische Untersuchung der Komplexe 2a - e erlaubt die Identifizierung der Stereochemie der Isomeren. - Die durch Monodeprotonierung von 2a (R = Me; m = 3; n = 1) und 2d(R = Me; m = 2; n = 1) mit KOH oder der OH- -Form eines Anionentauschers gebildeten Phosphidokomplexe 3a and d werden durch Luftsauerstoff zu den phosphanoxidophosphan-komplexen 4a und d oxidiert, bei denen zwei bzw. drei Konfigurationsisomere mit P-gebundenen Phosphanoxido-Einheiten Pd—P(O)Me— vorliegen.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141122
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  • 80
    Digitale Medien
    Digitale Medien
    Masthead (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981) 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141201
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  • 81
    Digitale Medien
    Digitale Medien
    Reaktionen mit Aziridinen (Aziranen), XXVI: Aminkatalysierte Amidoethylierungen von β-Dicarbonylverbindungen Eine einfache Synthese von 2-Methylpyrrol-1,3-dicarbonester (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3599-3608 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Reactions with Aziridines (Aziranes), XXVI: Amine Catalyzed Amidoethylation of β-Dicarbonyl Compounds Simple Synthesis of 2-Methylpyrrole-1,3-dicarboxylateEsters of nonsubstituted and monosubstituted malonic, cyanoacetic, and β-keto acids are easily C-amidoethylated by N-acylaziridines in the presence of triethylamine. In this amine catalyzed reaction the acylaziridines show different degrees of reactivity. Often the products cannot be obtained by the known amidoethylation procedure or but in smaller yields. The new product 3g may smoothly be converted to the pyrroline 9 and further to the 2-methylpyrrole-1,3-dicarboxylate 10. - Divergent from earlier results, the primary amidoethylation product can be isolated from the known sodium salt reaction of tert-butyl acetoacetate with nonbulky acylaziridines. This product is cleaved by trifluoroacetic acid with remarkable easiness to yield the corresponding amidoethyl derivative of acetone.
    Notizen: Unsubstituierte und monosubstituierte Malonester, Cyanessigester und β-Ketoester werden in Gegenwart von Triethylamin durch N-Acylaziridine leicht am C amidoethyliert, dabei zeigt sich eine Reaktivitätsabstufung der N-Acylaziridine. Die Produkte sind oft durch die bisher bekannte Amidoethylierung nicht oder nicht in so guten Ausbeuten zugänglich. Das neue Produkt 3g läßt sich glatt zum Pyrrolin 9 und weiter zum 2-Methylpyrrol-1,3-dicarbonester 10 umwandeln. - Abweichend von bisherigen Ergebnissen kann man aus Acetessigsäure-tert-butylester nach der bekannten Natriumsalzmethode auch mit nichtsperrigen Acylaziridinen das Primärprodukt fassen, das mit Trifluoressigsäure bemerkenswert leicht zum entsprechenden Amidoethylderivat des Acetons gespalten wird.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141113
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  • 82
    Digitale Medien
    Digitale Medien
    Elektrochemische Synthesen, XVIII: Reaktionen des Naphthalinradikalkations mit Nucleophilen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3643-3654 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Electrochemical Syntheses, XVIII: Reactions of the Radical Cation of Naphthalene with NucleophilesSolid naphthalene radical cation hexafluorophosphate at -77°C reacts with tetrabutylammonium cyanide, acetate, thiocyanate, and chloride in dichloromethane in up to 38% current efficiency referred to the corresponding naphthalene derivatives.
    Notizen: Festes Naphthalinradikalkation-hexafluorophosphat reagiert bei -77°C in Dichlormethan mit Tetrabutylammonium-cyanid,- acetat, -thiocyanat und -chlorid mit bis zu 38% Stromausbeute zu den entsprechenden Naphthalinderivaten.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141117
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  • 83
    Digitale Medien
    Digitale Medien
    Umlagerungen vinyloger Carbonsäurechloride, XXX: Thermische Umlagerungen von chlor- und organylthiosubstituierten (2Z, 4Z)-2,4-Pentadienalen und -onen zu (2Z, 4Z)-2,4-Pentadienthiosäure-S-estern (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3625-3633 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Rearrangements of Vinylogous Acyl Chlorides, XXX: Thermal Rearrangements of Chloro- and Organylthio-substituted (2Z, 4Z)-2,4-Pentadienals and -ones to (2Z, 4Z)-2,4-PentadienethioatesThe pentadienals 2 are prepared by reduction of the corresponding acyl Chlorides 1. The ketone 2d is synthesized from 1b with lithium tert-butyl(phenylthio)cuprate. Elimination of methyl chloride and cyclization occurs on treatment of 1a with AlCl3 giving the 2H-thiopyran-2-one 8. In boiling carbontetrachloride the aldehydes 2 rearrange by 1,5-chlorine shift completely and stereospecifically into the thioates 3. The analogous reaction 2d → 3d is no stereospecific. As expected, compounds 2 and 3 may be converted into the same 4H-pyran-4-ones 6. The rearrangement 2 → 3 is accelerated by RS-groups instead of chlorine in the 5-position and decelerated in the 3-position. The substituent influences and the reaction mechanism are discussed.
    Notizen: Die Pentadienale 2 werden durch Reduktion der entsprechenden Säurechloride 1, dargestellt. Das Keton 2d wird aus 1b mit Lithium-tert-butyl(phenylthio)cuprat synthetisiert. 1a spaltet unter der Wirkung von AlCl3 Methylchlorid ab und cyclisiert zum 2H-Thiopyran-2-on 8. Die Aldehyde 2 lagern sich in siedendem Tetrachlorkohlenstoff unter 1,5-Chlorwanderung vollständig und stereospezifisch in die Thioester 3 um. Die analoge Reaktion 2d → 3d ist nicht stereospezifisch. Erwartungsgemäß liefern die Verbindungen 2 und 3 die gleichen 4H-Pyran-4-one 6. Die Umlagerung 2 → 3 wird durch RS-Gruppen an Stelle von Chloratomen in 5-Stellung beschleunigt und in 3-Stellung verlangsamt. Die Substituenteneinflüsse und der Reaktionsmechanismus werden diskutiert.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141115
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  • 84
    Digitale Medien
    Digitale Medien
    Das Energieprofil des o-Chinodimethan ⇄ Benzocyclobuten-Gleichgewichtes, II (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3741-3750 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Energy Profile of the o-Quinodimethane ⇄ Benzocyclobutene Equilibrium, IIThe kinetics of the decomposition of keton 3 yielding o-quinodimethane (2) (Ea = 25.6 kcal/mol; A = 3.1 × 1013s-1) and its cyclisation to benzocyclobutene (1) (Ea = 26.9 kcal/mol; A = 2.1 × 1012 S-1) is measured by shock tube technic. From the temperature dependence of the equilibrium 1 ⇄ 2 which is studied by the same method, the enthalpy of formation of o-quinodimethane 2 is established to be ΔHfo (g) = 60.8 kcal/mol.
    Notizen: Mit Hilfe der Stoßrohr-Technik werden ausgehend vom Keton 3 Aktivierungsparameter für die Bildung des o-Chinodimethans (2) (Ea = 25.6kcal/mol; A = 3.1 × 10 13 S-1) und dessen Weiterreaktion zum Benzocyclobuten (1) (Ea = 26.9 kcal/mol; A = 2.1 × 1012 S-1) bestimmt. Mit der gleichen Technik wird aus der Temperaturabhängigkeit des Gleichgewichtes 1 ⇄ 2 die Bildungsenthalpie des o-Chinodimethans (2) zu ΔHfo (g) = 60.8 kcal/mol abgeleitet.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141202
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  • 85
    Digitale Medien
    Digitale Medien
    Stereoisomerisierungen von Keteniminen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3751-3771 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Stereoisomerization of Ketene IminesBarriers to racemization in solution of the ketene imines 1a-y and X-ray structures of the ketene imines 1s and z are described. Similar to allenes all ketene imines have dihedral angles of 90° between the C-and N-substituents. The barriers to racemization range from 30 to 63 kJmol-1 and are lowered by electron attracting substituents on C and N. The barriers of m-and p-substituted N-arylketene imines give a linear Hammett correlation with σ- constants. N-Arylketene imines racemize through inversion at nitrogen and simultaneous rotation of the aryl group around the N- aryl bond.
    Notizen: Es werden Racemisierungsbarrieren der Ketenimine 1a-y in Lösung und Röntgenstrukturanalysen der Ketenimine 1s und z beschrieben. Alle Ketenimine haben ein allenartig gewinkeltes Molekülgerüst mit Torsionswinkeln von 90° zwischen den C- und N-Substituenten. Die Racemisierungsbarrieren (ΔG≠) liegen zwischen 30 und 63 KJmol -1 und werden durch elektronenziehende Substituenten am C- und N-Ende erniedrigt. Die Racemisierungsbarrieren m-und p-substituierter N-Arylketenimine korrelieren nach Hammett linear mit σ- - Werten. N-Arylketenimine racemisieren durch inversion am Stickstoff und synchrone Rotation des Arylrestes um die N-Arylbindung.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141203
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  • 86
    Digitale Medien
    Digitale Medien
    Alkine und Cumulene, XV: Über die Photodimerisierung konjugierter Enine (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3772-3788 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Alkynes and Cumulenes, XV: On the Photodimerization of Conjugated EnynesOn irradiation in the presence of triplet sensitizers having a triplet energy 〉 250 KJ/mol, vinylacetylene (1a) dimerizes to cis-and trans-1,2-diethynylcyclobutane (cis and trans-2) as well as minor amounts of 4-ethynyl-1-vinylcyclobutene (3). The effect of substituents on the course of the reaction is investigated: whereas alkyl, vinyl, and phenyl substituents, respectively, in the 4-position of 1a do not influence the photoaddition, 2-substituted enynes yield the corresponding cyclobutanes in poor yields only. Finally, 1-substituted vinylacetylenes (besides the substituents mentioned above the influence of ethynyl, chloro, and methoxy groups has been investigated) do not provide photodimers; they are cis-trans-isomerized instead. The mechanism of the photoaddition is discussed.
    Notizen: Vinylacetylen (1a) dimerisiert bie Bestrahlung in Gegenwart von Triplettsensibilisatoren mit einer Triplettenergie 〉 250 KJ/mol zu cis- und trans-1,2-Diethinylcyclobutan (cis- und trans-2) sowie kleineren Mengen an 4-Ethinyl-1-vinylcyclobuten (3). Die Auswirkung von Substituenten auf diese Reaktion wird untersucht: während Alkyl-, Vinyl- und Phenylsubstituenten in 4-Stellung von 1a keinen Einfluß auf die Photoaddition haben, dimerisieren 2-substituierte Enine nur noch in schlechten Ausbeuten zu den entsprechenden Cyclobutanen. Schließlich bilden. 1-Substituierte Vinylacetylene (außer den obigen Substituenten wurde der Einfluß von Ethinyl-, Chlor - und Methoxyresten untersucht) keine Photodimeren, sondern werden lediglich cis-trans-isomerisiert. Der Mechanismus der Photoaddition wird diskutiert.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141204
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  • 87
    Digitale Medien
    Digitale Medien
    Wanderungstendenzen cyclischer, polycyclischer und methylverzweigter Alkylreste bei der Beckmann-Umlagerung (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3831-3854 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Migration Aptitudes of Cyclic, Polycyclic, and Branched Alkyl Groups in the Beckmann RearrangementsThe migration aptitudes of polycyclic bridgehead groups, cycloalkyl groups as well as of β-γ-and δ-branched alkyl groups in the Chapman variant of the Beckmann rearrangement were determined. From these data it is concluded that at transition state 2 the migrating group is not resembling a planarised carbenium ion R+, but rather a pentacoordinated carbonium ion structure. Because only small geometrical changes occur in the migrating group vertical stabilisation4) of charge at transition state is believed to have significant influence on the migration aptitudes.
    Notizen: Die Wanderungstendenzen von polycyclischen Brückenkopfresten, Cycloalkylresten sowie β, γ-und -δ-verzweigten Alkylresten bei der Chapman-Variante der Beckmann-Umlagerung wurden bestimmt. Sie zeigen, daß die wandernde Gruppe im Übergangszustand 2 nicht Carbenium-Ionen-Charakter hat, sondern nach weitgehender Beibehaltung ihrer Geometrie eher einer Fünffach koordinierten Carboniumstruktur entspricht, die im Zuge der Umlagerungsreaktion vertikal stabilisiert4 werden kann.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141208
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  • 88
    Digitale Medien
    Digitale Medien
    Vom Ionenpaar zum Radikalkomplex: Koordinationsverbindungen des reduzierten 2,2′-Bipyridins mit Organometall-Kationen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3789-3800 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: From Ion Pairs to Radical Complexes: Coordination Compounds of Reduced 2,2′-Bipyridine with Organometallic CationsReduced 2,2′-bipyridine, bipy-·, forms paramagnetic complexes with organometallic cations RnM+ containing metals of the first three groups of the periodic system (n = 0, 1,2). The persistent radicals [RnM)bipy]· have been identified and studied by high resolution electron spin resonance. Their ESR coupling constants can be correlated excellently with results from HMO calculations and exhibit a typical sequence of cations RnM+: K+, Na+, Li+, PhMg+, PhZn+, Me2Ga+, PhBe+, Ph2B+, R2Al+. This series exemplifies the continuous variation from genuine paramagnetic „ion pairs“ mostly covalently bonded radical complexes.
    Notizen: Reduziertes 2,2′-Bipyridin, bipy-·, bildet paramagnetische Komplexe mit metallorganischen Kationen RnM+ aus den ersten drei Gruppen des Periodensystems (n = 0, 1, 2). Die beständigen Radikale [(RnM) bipy]· lassen sich durch hochauflösende Elektronenspinresonanz nachweisen und untersuchen. Ihre ESR-Kopplungskonstanten können vorzüglich mit den Ergebnissen von HMO-Berechnungen korreliert werden, man erhält so eine charakteristische Reihenfolge der Kationen RnM+: K+, Na+, Li+, PhMg+, PhZn+, Me2Ga+, PhBe+, Ph2B+, R2Al+. Diese Serie überdeckt lückenlos den Bereich von echten, paramagnetischen „Ionenpaaren“ bis hin zu überwiegend kovalent aufgebauten Radikalkomplexen.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141205
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  • 89
    Digitale Medien
    Digitale Medien
    Borimide und Borylnitrene beim Zerfall von Diaminoazidoboranen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3801-3812 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Boron Imides and Borylnitrenes by Decomposition of DiaminoazidoboranesGas phase thermolysis of azidoboranes (R2N)2BN3 (1a, b) at 450-485°C gives the products 2a (by retro ene-reaction) and 4b (by intramolecular 1,2-alkylohydrogenation), respectively, both from boron imides R2N—B=N—NR2 (9a, b) as intermediates; furthermore, 3a is isolated from the thermolysis of 1a via a borylnitrene (R2N)2B—N by intramolecular 1,1-alkylohydrogenation. The photolysis of 1a, b generates the borylnitrenes 10a, b as intermediates, which are stabilized by an intermolecular reaction to 7a and 8b, respectively; the nitrene 10a can be trapped by ethyloboration with BEt3.
    Notizen: Bei der Gasphasenthermolyse der Azidoborane (R2N)2BN3 (1a, b) bei 450-485°C erhält man Produkte 2a bzw. 4b, die aus den Borimiden R2N — B = N — NR2 (9a, b) durch eine Retro-En-Reaktion bzw. durch eine intramolekulare 1,2-Alkylohydrierung der B=N-Bindung hervorgehen; die Thermolyse von 1a führt daneben zu 3a, einem Folgeprodukt der intramolekularen 1,1-Alkylohydrierung des entsprechenden Borylnitrens (R2N)2B—N. Die Photolyse von 1a, b ergibt die Borylnitrene 10a, b als Zwischenstufen, die intermolekular zu 7a bzw. 8b weiterreagieren; das Nitren 10a läßt sich mit BEt3 durch Ethyloborierung abfangen.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141206
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  • 90
    Digitale Medien
    Digitale Medien
    Alkylwanderungen bei Sextettumlagerungen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3813-3830 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Migration of Alkyl Group in Sextett RearrangementsThe migration aptitude of alkyl groups in the Beckmann-, the Criegee-, and the isonitrile-nitrile rearrangements were investigated. The relative rearrangement rates of substituted benzyl groups are an expression of the charge on the migrating carbon at transition state. From the relative rates of migration of exo- and endo- 2- norbornyl group the geometrical changes at the migrating carbon are estimated. Finally, The different influence of α-branching in the migrating group is discussed for these and some other rearrangements.
    Notizen: Die Wanderungstendenzen von Alkylgruppen bei der Beckmann- Criegee- und Isonitril-Nitril-Umlagerung werden untersucht. Aus den relativen Reaktionsgeschwindigkeiten der substituierten Benzylreste werden Rückschlüsse auf die Ladungsverteilung im Übergangszustand dieser Reaktionen gezogen und aus dem Verhältnis der Wanderungstendenzen des exo und endo- 2- Norbornylrestes auf die Geometrie der wandernden Gruppe im Übergangszustand. Der in verschiedenen Sextettumlagerungen unterschiedliche Einfluß der α-Methylverzweigung in der wandernden Gruppe wird interpretiert.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141207
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  • 91
    Digitale Medien
    Digitale Medien
    Darstellung und Eigenschaften von und Reaktionen mit metallhaltigen Heterocyclen, XXI: Ringkontraktion, Kristallstrukturen, Eigenschaften und Stabilität von Manganacycloalkanen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3855-3862 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Preparation and Properties of, and Reaction with, Metal-Containing Heterocycles, XXI: Ring Contraction, Crystal Structures, Properties, and Stability of ManganacycloalkanesWhen the manganacyclohexane derivative (1) is warmed in a sealed tube to 100°C in n-hexane it is changed, probably via a hydridic alkenyl step, to the ring-contracted cyclopentane (2). Crystals of 1 and 2 are orthorhombic and monoclinic, space groups P212121 and P21/c, respectively, with Z = 4. In the Mn — C σ bond of 2 CO and SO2 can be inserted with formation of the cyclic compounds (3) and (4).
    Notizen: Das Manganacyclohexan-Derivat (1) lagert sich beim Erwärmen im Einschlußrohr auf 100°C in n-Hexan, wahrscheinlich über eine hydridische Alkenylstufe, zum ringverengten Cyclopentan (2) um. 1 und 2 kristallisieren orthorhombisch bzw. monoklin in den Raumgruppen P212121 bzw. P21/c mit Z = 4. In die Mn — C-σ-Bindung von 2 läßt sich CO und SO2 einschieben unter Bildung der cyclischen Verbindungen (3) und (4).
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141209
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  • 92
    Digitale Medien
    Digitale Medien
    Umsetzungen mit Monohydrazonen von Dicarbonylverbindungen, X: 2-(Dimethylhydrazono)propanal als Reagens zur Synthese von 1,4-Diketonen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3863-3877 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Reactions with Monohydrazones of Dicarbonyl Compounds, X: 2-(Dimethylhydrazono)propanal as a Reagent for the Synthesis of 1,4-DiketonesMonohydrazones 7 of unsaturated 1,4-diketones can be prepared by the reaction of methyleneactive ketones 1a-x with 2-(dimethylhydrazono)propanal (5a). From these products unsaturated 8 and saturated 1,4-diketones (9) are obtained in high yield. Reduction of the diketone monodimethylhydrazones 7g, h, i, p, q with sodium borohydride and subsequent hydrolysis leads to the formation of furans 23and/or N-aminopyrroles 24. The synthesis of a Δ1-pyrrolin 30, which was isolated from the poison gland of the South African thief ant Solenopsis punctaticeps is described7.
    Notizen: 2-(Dimethylhydrazono)propanal (5a) läßt sich mit CH-aciden Verbindungen 1a-x, die eine α-ständige Methylengruppe enthalten, zu Hydrazonopropyliden-Derivaten 7a-x umsetzen. Durch Hydrolyse erhält man ungesättigte, 1,4-Diketone 8 und durch deren Reduktion gesättigte 1,4-Diketone 9. Die Monohydrazone 7g, h, i, p, q ergeben nach Borhydrid-Reduktion und Hydrolyse Furane 23 und / oder N-Aminopyrrole 24. Katalytische Hydrierung des Diketon-monodimethyl hydrazons 29 liefert das Δ1-pyrrolin 30, ein Abwehrstoff der aus der Giftdrüse der südafrikanischen Feuerameise Solenopsis punctaticeps isoliert wurde7.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811141210
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  • 93
    Digitale Medien
    Digitale Medien
    Molekül- und Kristallstrukturen zweier Carbodiphosphorane mit P—C—P-Bindungswinkeln nahe 120° (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3070-3078 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Molecular and Crystal Structures of Two Carbodiphosphoranes with P—C—P Bond Angles Near 120°sym-Dimethyltetraphenylcarbodiphosphorane (1) and the cyclic carbodiphosphorane 2 show in the crystalline state the smallest P=C=P bond angles (121.8(3) and 116.7 (7)°, respectively) observed so far among compounds of this type. The lengths of the ylidic P=C bonds (164.8 (4) pm in 1, 164.5 (12) and 165.3 (14) pm in 2) are within the double bond range. In 1 two phenyl rings are parallel with a mutual distance of 328 pm; in the crystal phenyl ring layers are formed. This favourable packing of the phenyl groups should be the reason for the small P—C—P bond angle, whose easy bending is thus demonstrated again.
    Notizen: sym-Dimethyltetraphenylcarbodiphosphoran (1) und das cyclische Carbodiphosphoran 2 haben im Kristall mit 121.8 (3) bzw. 116.7 (7)° die kleinsten P=C=P-Bindungswinkel, die bisher bei Vertretern dieser Verbindungsklasse gefunden wurden. Die ylidischen P=C-Bindungslängen (164.8 (4) pm bei 1, 164.5 (12) bzw. 165.3 (14) pm bei 2) liegen im Doppelbindungsbereich. Bei 1 sind zwei Phenylringe mit einem Abstand von 328 pm parallel zueinander; im Kristall bilden sich Phenylring-Schichten aus. Diese günstige Packung der Phenylgruppen dürfte die Ursache für den kleinen P—C—P-Bindungswinkel sein, dessen leichte Deformierbarkeit damit erneut unter Beweis gestellt wird.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811140914
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  • 94
    Digitale Medien
    Digitale Medien
    Natürlich vorkommende Terpen-Derivate, 3061) Synthese eines Furansesquiterpens aus Eumorphia prostata (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 227-231 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Naturally Occuring Terpene Derivatives, 3061) Synthesis of a Furan Sesquiterpene from Eumorphia prostataStarting with 5-methyl-2-cyclohexen-1-one (1) through the intermediate 4 the cyclopentene carbaldyhydes 5 und 6 were synthesized. Wittig reaction led to the epimeric nitriles 7 und 8, which after conversion to the aldehydes 9 and 10 on reaction with β-furyllithium afforded the carbinols 11 and 12. Manganese dioxide oxidation yielded the ketones 13 and 14, their spectral data being in agreement with those of the natural compounds.
    Notizen: Ausgehend von 5-Methyl-2-cyclohexen-1-on (1) werden über das Zwischenprodukt 4 die Cyclopentancarbaldehyde 5 und 6 synthetisiert. Wittig-Reaktion führt zu den epimeren Nitrilen 7 und 8, die nach Überführung in die Aldehyde 9 und 10 durch Reaktion mit β-Furyllithium die Carbinole 11 und 12 liefern. Mangandioxid-Oxidation gibt die Ketone 13 und 14, deren spektroskopischen Daten mit denen der Naturstoffe übereinstimmen.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811140124
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  • 95
    Digitale Medien
    Digitale Medien
    Über die Umsetzung von Benzofuroxan mit Ketonen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 246-253 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Reaction of Benzofuroxan with KetonesReaction of branched-chain ketones 4 with benzofuroxan (1) in the presence of ammonia yields o-quinoid 2-amino-2,3-dihydro-2,3,3-trialkylquinoxaline 1,4-dioxides 6. The same procedure with KOH catalysis gives the corresponding 2-hydroxy compounds. A synthesis of spiro compounds 16 by using acetylcycloalkanes 15 in this reaction is described. Under different reaction conditions. the reduction products of these compounds were 1,2-dihydro-2,2,3-trialkyl-1-quinoxalinol 4-oxides 19, 22, 23, 1,2,3,4-tetrahydro-2,2,3-trialkylquinoxalines 21, 24, 25 and 1,2-dihydro-2,2,3-trialkylquinoxalines 20, 26.
    Notizen: Durch Umsetzung von verzweigten Ketonen 4 mit Benzofuroxan (1) in Gegenwart von Ammoniak werden o-chinoide 2-Amino-2,3-dihydro-2,3,3,-trialkylchinoxalin-1,4-dioxide (6), in Gegenwart von KOH die analogen 2-Hydroxyverbindungen erhalten. Der Einsatz von Acetylcycloalkanen (15) führt zur Synthese von Spiroverbindungen 16. Als Reduktionsprodukte der genannten Verbindungen werden 1,2-Dihydro-2,2,3-trialkyl-1-chinoxalinol-4-oxide 19, 22, 23, 1,2,3,4-Tetrahydro-2,2,3-trialkylchinoxaline 21, 24, 25 und 1,2-Dihydro-2,2,3-trialkylchinoxaline 20, 26 bei unterschiedlichen Reaktionsbedingungen erhalten.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811140127
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  • 96
    Digitale Medien
    Digitale Medien
    Synthesen, ESR- und ENDOR-Untersuchungen hochverdrillter phenylsubstituierter Radikalanionen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 254-266 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Syntheses ESR, and ENDOR Studies of Highly Twisted Phenyl Substituted Radical AnionsThe synthesis of a variety of phenyl substituted and partially deuterated derivatives of anthracene. naphthalene benzo[b]triphenylene, and benzo[k]fluoranthene is given. By performing ESR, ENDOR, and TRIPLE experiments the hyperfine coupling constants, including their signs, of the respective radical anions are determined. Regarding the spin distributions within the phenyl substituents it is shown that the conventional sequence of the hyperfine couplings |HparaH|≥ |HaorthoH| 〉 |HmetaH| is not always valid. These results are interpreted in terms of a significant π-σ-mixing, i. e. a phenyl hyperconjugation effect.
    Notizen: Die Synthese phenylsubstituierter, zum Teil deuterierter Abkömmlinge des Anthracens, des Naphthalins, des Benzo[b]triphenylens und des Benzo[k]fluoranthens wird beschrieben. Mit Hilfe von ESR-, ENDOR- und TRIPLE-Experimenten werden die Hyperfeinkopplungskonstanten der korrespondierenden Radikalanionen einschließlich ihrer relativen Vorzeichen bestimmt und den jeweiligen Molekülpositionen zugeordnet. Für einige der untersuchten Systeme wird gezeigt, daß in der Spindichteverteilung der Phenylsubstituenten verdrillungsbedingte Abweichungen von der konventionellen Sequenz |HparaH|≥ |HaorthoH| 〉 |HmetaH| auftreten, die mit einer Phenylhyperkonjugation gedeutet werden können.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811140128
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  • 97
    Digitale Medien
    Digitale Medien
    Borimide beim thermischen Zerfall der Dialkyl[silyl(Silyloxy)-amino]borane (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 298-305 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Boron Imides from the Thermal Decomposition of Dialkyl[sily(silyloxy)amino]boranesDialkyl[trimethylsilyl)(trimethylsilyloxy)amino]boranes R2B—N(OSiMe3SiMe3 (1a-c), prepared from (Me3Si)2N—OSiMe3 and R2BCl, can be thermolyzed in the liquid phase at 70°C to form (Me3SI)2O and a mixture of R2B—NR—Br—N(OSiMe3)SiMe3 (2a-c) and (RBNR)3 (3a-c). In the presence of an excess of BR′3, 1b, c can be transformed into (Me3Si)2O and diborylamines RR′B—NR—BR′2 (4b), c, (Me3Si)2O and a mixture of (RBNR)3 and polymer material are formed from the gas-phase thermolysis of 1b, c at 270°C The polymer (EtBNEt)n depolymerizes to the borazine 3b above 150°C. An intermediate from the gas-phase thermolysis of 1b can be trapped by liquid 1c, yielding 2c, A. conclusive explanation of all these observation is possible by the assumption that boron imides RB—NR(5a-c) occur as intermediates.
    Notizen: Die aus (Me3Si)2N-OSiMe3 und R2BCl zugänglichen Dialkyl[trimethylsilyl)(trimethylsilyloxy)amino]borane R2B—N(OSiMe3)SiMe3 (1a-c zerfallen in flüssiger Phase bei 70°C unter Abspaltung von (Me3Si)2O in ein Gemisch aus R2B—NR—BR—N(OSiMe3)SiMe3 (2a-c) und (RBNR)3 (3a-c). Im Überschuß von BR′3 erhält man aus 1b, c neben (Me3Si)2O die Diborylamine RR′B—NR—BR′2 (4b-c). In der Gasphase entstehen bei 270°C aus 1b, c (Me3Si)2O und ein Gemisch aus (RBNR)3 und Polymeren. Das Polymere (EtBNEt)n depolymerisiert oberhalb 150°C zu 3b. Flüssiges 1c regiert mit einer aus 1b durch Gasphasenthermolyse gebildeten Zwischenstufe zum Abfangprodukt 2c′. Einer geschlossenen Deutung aller Befunde liegt die Annahme von Borimiden RB—NR (5a-c) als Zwischenstufen zugrunde.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811140133
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  • 98
    Digitale Medien
    Digitale Medien
    Bausteine von Oligosacchariden, XXI1) Synthesen von Gentamicin X2 und am C-4′ und C-3′ modifizierter Gentamicine (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 322-332 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Building Units for Oligosaccharides, XXI1) Syntheses of Gentamicin X2 and Gentamicins Modified At C-4′ and C-3′The garamine derivative 18 can be coupled with the β-chloride 15 of 2-azido-2-deoxy-D-glucose to 20 from which, by deblocking procedure, gentamicin X2 (23) is available. In the same manner the 4′-amino- and 4′-chloro compound 24 and 25, resp., can be obtained. Coupling of 26 with 19 gives the product 27 from which the derivative 28 of gentamicin, modified at C-3′, is prepared.
    Notizen: Das Garamin-Derivat 18 läßt sich mit dem β-Chlorid 15 der 2-Azido-2-desoxy-D-glucose zu 20 kuppeln, aus dem durch Entblockierung Gentamicin X2 (23) erhältlich ist. Auf gleichem Wege ist die 4′-Amino- und 4′-Chlorverbindung 24 bzw. 25 zu gewinnen. Ein am C-3′ modifiziertes Derivat 28 des Gentamicins ist nach Kupplung von 26 mit 19 aus dem Produkt 27 zugänglich.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811140135
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  • 99
    Digitale Medien
    Digitale Medien
    Bausteine von Oligosacchariden, XX1) Synthese der Oligosaccharid-Determinanten der Blutgruppensubstanzen der Type 2 des ABH-Systems. Diskussion der α-Glycosid-Synthese (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 306-321 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Building Units for Oligosaccharides, XX1) Synthesis of the Oligosaccharide Determinants of Blood Group Substances of Type 2 of the ABH System. Discussion of α-Glycoside SynthesisThe antigenic determinants of type 2 of blood-group substances A and B (23 and 24) (see German Summary) as well as blood-group substance H (17) were synthesized by selective glycosidation reactions combined with a series of blocking and deblocking steps. The possibilities and optimization of the α-glycoside synthesis are discussed. In hemagglutination inhibition tests the synthetic haptens A and B of type 2 and type 1 show a similar selective inhibitory effect. In case of hapten H, however, great differences can be observed. Here the type 2 exhibited a strong inhibition activity, whereas type 1 only showed an extremely low activity. The leads to the conclusion that in the determinants of the ABH-system on the surface of erythrocytes the chemical structure of type 2 is predominating.
    Notizen: Durch eine Folge von selektiven Glycosid-Synthesen, kombiniert mit einer Serie von Blockierungs-und Entblockierungsschritten wurden die Determinanten der Type 2 der Blutgruppensubstanzen A und B und H α-L-Fuc-(1-2)-β-D-Gal-(1-4)-D-GlcNac (17) synthetisiert. Die Möglichkeiten und die Optimierung der α-Glycosid-Synthese werden diskutiert. Im Hämagglutinations-Inhibitionstest zeigen die synthetischen Haptene A und B der Type 2 und Type 1 eine ähnliche selektive Hemmwirkung. Starke Unterschiede sind aber beim Hapten H zu beobachten. Hier hemmt die Type 2 sehr stark, die Type 1 dagegen äußerst schwach. Hieraus ist zu schließen, daß in den Oberflächendeterminanten des ABH-Systems der Erythrozyten die chemische Struktur der Type 2 dominiert.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811140134
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  • 100
    Digitale Medien
    Digitale Medien
    Synthese von optisch aktiven Trogoderma-Pheromonen durch Kolbe-Elektrolyse1) (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 292-297 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Synthesis of Optically Active Trogoderma pheromones by Kolbe-Electrolysis1)The (R)-(-)-enantiomers of (Z)- (1) and (E)-14-methyl-8-hexadecen-1-ol (2) have been synthesized by coelectrolysis of (R)-(-)-4-methylhexanoic acid (7) with 12-(tetrahydro-2-pyranyloxy)-4-dodecynoic acid (8) and its subsequent hydrogenation. The acid 7 was prepared in high optical purity from (S)-(-)-citronellol (3) by conversion of the hydroxyl group to a methyl substituent and subsequent clevage of (R)-(-)2,6-dimethyl-2-octene (4) with ozone. By alkylation of 4-pentynoic acid (5) with 1-bromo-7-(tetrahydro-2-pyranyloxy)heptane (6) the alkynoic acid 8 was synthesized.
    Notizen: Die (R)-(-) Enantiomeren des (Z)- (1) und (E)-14-Methyl-8-hexadecen-1-ols (2) wurden durch Coelektrolyse von (R)-(-)-4-Methylhexansäure (7) mit 12-(Tetrahydro-2-pyranyloxy)-4-dodecinsäure (8) und nachfolgende Hydrierung synthetisiert. Die Säure 7 wird in hoher optischer Reinheit ausgehend von (S)-(-)-Citronellol (3) durch Reduktion der Alkoholfunktion zur Methylgruppe und anschließende ozonolytische Spaltung des (R)-(-)-2,6-Dimethyl-2-octens (4) gewonnen. Durch Alkylierung von 4-Pentinsäure (5) mit 1-Brom 7-(tetrahydro-2-pyranyloxy) heptan (6) läßt sich die Alkinsäure 8 darstellen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19811140132
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