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  • 1985-1989  (1,047)
  • 1980-1984
  • 1988  (1,047)
  • Organic Chemistry  (765)
  • Atomic, Molecular and Optical Physics  (222)
  • Gas chromatography
  • Nuclear reactions
Material
Years
  • 1985-1989  (1,047)
  • 1980-1984
Year
  • 1
    ISSN: 1432-0738
    Keywords: Identification ; Quantification ; Ethyleneglycol ; Diethylene glycol ; Gas chromatography ; Mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A method for the gas chromatographic-mass spectrometric identification and quantification of ethylene glycol and diethylene glycol in plasma is described. Such a method is necessary in clinical and forensic toxicology to diagnose probable intoxication and to control the efficacy of detoxification. For sample preparation, the glycols were isolated using acetone after the addition of 1,3-propylene glycol as internal standard. The glycols were then esterified by pivalic acid (pivalic acid anhydride, triethylamine and methanol, 70° C, 15 min) to improve their gas chromatographic characteristics. The glycols were first identified by a comparison of the full mass spectra with reference spectra and then quantified. Therefore, the peak area ratio in the total ion chromatogram (ethylene glycol or diethylene glycol/1,3-propanediol) of the sample was compared with the calibration curve in which the peak area ratios of the standards (0.05, 0.1, 0.5, 1 and 2 g/l), prepared in the same way, were plotted versus their concentrations. The method was linear at least from 0.05 to 2 g/l, with a detection limit of 〈0.01 g/l. The analytical recoveries were 99.2–102.9% for the different concentrations. Precision studies show coefficients of variation of 3.0–6.3% for the different concentrations.
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  • 2
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    Springer
    Chromatographia 25 (1988), S. 21-24 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sample concentration ; Chromatographic evaporation ; Solvent effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several micro-techniques for the removal of solvent from dilute solutions of volatile compounds have been compared. Large solute losses were experienced when the conventional blow-down technique was applied. Better yields could be obtained with static evaporation procedures, as long as an effective reflux was maintained. However, careful optimization of the vessel design and operating conditions is necessary. The most efficient volume reduction technique was shown to be chromatographic evaporation. Quantitative recoveries were obtained for the compounds tested and the process was significantly faster than static concentration. Moreover, operating conditions (gas flow, temperature) are less critical. With modifications, the principle can be used for the concentration of large sample volumes down to a few microliters.
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  • 3
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Preparative scale separations ; Plate model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two close-boiling materials, diethyl ether (DEE) and dichloromethane (DCM), were separated to investigate the effects of the pure components and the mixture on elution in preparative gas-liquid chromatography. Nitrogen was used as the carrier gas, and the chromatographic column (1 cm I.D. and 0.75m length) was packed with Chromosorb A with different quantities of dinonyl phthalate stationary phase and particle sizes. Below ca. 7% (by wt.) of feed concentration, the experimental elution curves of pure DEE and DCM were almost the same as those of the mixture, and the theoretical plate model can be used successfully to predict the elution curves.
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  • 4
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index ; Hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of hydrocarbons present in the C5 pyrolysis fraction of gasolines on the stationary phases squalane and methylsilicone oil JXR at 30, 40 and 50°C was investigated by capillary gas chromatography. The unified retention indices of the hydrocarbons were also calculated on squalane. The retention indices obtained on these two phases were interrelated and the quantitative relationship with the structure of the solutes was studied. Equations based on the unified retention indices calculated on squalane and some selected structural elements of the solutes permit the calculation of their retention on methylsilicone with sufficient accuracy.
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  • 5
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    Springer
    Chromatographia 25 (1988), S. 404-408 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Silica surface modification ; Hexamethylcyclotrisilazane ; Hexamethyldisilazane ; Support materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper is concerned with the structure of an organic layer bonded to the silica surface modified with silazanes. The changes of the retention volumes of hydrocarbons is studied for the silicas modified with hexamethylcyclotrisilazane, hexamethyldisilazane and their mixtures. It is shown that most of the carbon in the layer after hexamethylcyclotrisilazane modification is bonded to the surface by Si−O−Si bonds. This fact supports the assumption of a fragmentation of the cyclosilane used for modification.
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  • 6
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    Springer
    Chromatographia 25 (1988), S. 609-612 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Triglyceride composition of grapes ; Identification system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The triglyceride composition of the Tempranillo grape (Vitis vinifera) has been examined by a combination of HPLC and GLC. To identify the triglycerides, equations were applied relating log k′ with the molecular variables: equivalent carbon number, chain length and number of double bonds in each of the fatty acids in the glycerides. Ten triglycerides were found, the principal ones being trilinolein (35.75%), dilinoleyl-olein (21.03%) and dilinoleyl-palmitin (17.02%).
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  • 7
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    Springer
    Chromatographia 25 (1988), S. 655-658 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Structure-retention relationships ; Connectivity indices, topological indices ; Alkenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention indices of different alkenes are correlated with connectivity and topological parameters. The appropriate statistically valid relations hips are derived and discussed.
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  • 8
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    Springer
    Chromatographia 26 (1988), S. 34-36 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas analysis in halogen lamps ; Sampling device
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new type of gas sampling device was constructed to improve the analysis of the gas in halogen lamps. Low levels of gases such as O2, CH4, C2H4 and CH3Br could be determined by the techniques worked out.
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  • 9
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    Springer
    Chromatographia 26 (1988), S. 229-233 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Glass capillaries ; Chirasil-Val ; Immobilisation ; Enantiomeric separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Immobilisation methods of the chiral silicone stationary phase Chirasil-L-Val have been studied. In addition to the standard techniques of radical-induced immobilisation with dicumyl peroxide and azo tert-butane, immobilisation was solely achieved by thermal treatment: conditioning at low flow-rates or under stop-flow conditions led to unexpectedly high immobilisation despite mild temperatures. The presence of water vapor in the carrier gas accelerated the immobilisation process. While up to 75% immobilisation was attainable with both ATB and thermal methods, immobilisation with DCUP did not exceed 50%, despite relatively high DCUP concentrations. Whilst all immobilisation methods were accompanied by varying degrees of racemisation at the chiral centre, it was possible to establish conditions that yielded a high immobilisation (in excess of 70%) with a negligible loss in enantiomeric selctivity. The immobilisation reactions also slightly affected the polarity of the stationary phase, reflected in a shift of the Kovats-Indices of amino acid derivatives and in the accompanying “Squalane-Effect”. With respect to immobilisation, racemisation and polarity shift, thermal immobilisation with water-saturated carrier gas proved to be the optimum method.
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  • 10
    ISSN: 1612-1112
    Keywords: Gas chromatography ; On-line process analysis ; Injection of volatile compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified on-line liquid injection technique with rotary valves for gas chromatography has been developed. Applications for the on-line analysis of 2-methylpropene, cyclohexene and 1-butene are described. All samples were loaded under pressure. The results obtained show excellent reproducibility with less than 0.1% relative standard deviation (r.s.d.; n=6) for the peak areas measured. The method is particularly advantageous for samples containing both gas and liquid ccomponents at one bar.
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  • 11
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    Springer
    Chromatographia 25 (1988), S. 313-318 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index ; Slope of log plot ; Homologous series ; Partition coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The slope of the n-alkane log plot dt′R/dnc (t′R=adjusted retention time; nc=carbon number) for a stationary phase can be used to obtain the retention index of an unidentified substance in a chromatogram containing only one peak with a known retention index, or to predict the retention time of a substance from that of a different homolog in the same series. It can also be used to translate retention indices into relative retention time, partition coefficient or specific retention volume. Published values of the slope are collected and critically evaluated. Equations are deduced that predict its approximate value at a specified temperature given the value at only one other temperature.
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  • 12
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Glass capillary columns ; Bile acids ; Hexafluoroisopropyl esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified gas chromatographic glass capillary technique for determination of five major bile acids (Cholic acid: CA, Chenodeoxycholic acid: CDCA, Deoxycholic acid: DCA, Lithocholic acid: LCA and Ursodeoxycholic acid: UDCA) has been developed after preliminary extraction with XAD-2 resin. Enzymatic hydrolysis prevents the formation of interferring degradation products. Ether extraction with centrifugation eliminates water soluble interferring substances. Derivatization to hexafluorpropyl- instead of methyl esters results in better separation, shortens analysis time and prolongs the life span of the column.
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  • 13
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    Springer
    Chromatographia 25 (1988), S. 598-602 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Capillary columns ; Steroid profiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Steroid conjugates are hydrolysed enzymatically using β-glucuronidase after extraction from urine using a solid phase extraction cartridge. After hydrolysis the free steroids are removed from the matrix, again utilising solid phase extraction. Derivatisation of the free hydroxyl groups using Hydrox-Sil AQ produces the respective TMS ethers which are extracted into hexane, in which solvent they are stable for many days. Capillary GC analysis with flame ionisation detection produces a profile of the steroids present in the sample. This technique is suitable for following changes in the urinary excretion profiles of patients undergoing investigation for a variety of steroid production-related diseases.
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  • 14
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    Springer
    Chromatographia 25 (1988), S. 539-542 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Temperature programming ; Retention index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is presented for the calculation of retention indices at an assigned temperature from temperature-programmed data. If the retention times at two different program rates for the solutes and the n-alkanes are known, the retention indices at an assigned temperature can be calculated directly.
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  • 15
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    Chromatographia 25 (1988), S. 589-592 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Hold-up time determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary New versions are suggested for the gas hold-up time calculation in gas chromatography. The results are compared with those obtained by using other methods. The advantages of the suggested ways of calculation are pointed out.
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  • 16
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    Chromatographia 25 (1988), S. 618-620 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Toluenesulfonic acid isomer distribution ; Ethyl toluenesulfonate isomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method for the determination of isomeric distribution in toluenesulfonic acid samples is described. The acids are transformed into the corresponding ethyl esters by reaction with triethyl orthoformate in toluene. The reaction mixture can be injected, without further purification, into the gas chromatograph. The separation is best performed on columns containing OV-210 or polyphenyl ether (6 rings) as the stationary phase.
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  • 17
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    Chromatographia 25 (1988), S. 725-730 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Structure-retention correlation ; Kováts retention index ; Alkylaromatics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Relative retention data and Kováts retention indices were measured for several hydrocarbons (mainly for alkylbenzenes) on dinonylphtalate and polyethylenelycol 4000 stationary phase. Correlations were searched between these retention data and the following physical (boiling point, molrefraction, molvolume) and topological (connectiviity index and general index of molecular complexity) properties of solutes. The best fitting equations was choosen among more than 150 equations involving linear, quadratic, exponential, two variables linear and quadratic dependence of retention data and the properties mentioned as well as their inverses.
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  • 18
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid crystals ; Thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Thermodynamic properties of 22 solutes at infinite dilution have been determined in the smectic, nematic and isotropic mesophases of 4,4′-bis(heptyloxy)azoxybenzone. The thermodynamic properties are discussed in relation to the solute-solvent (liquid crystal) interactions as conditioned by the degree of order in the liquid crystal.
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  • 19
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Perhalogenated compounds ; Relative retentions ; Identification by interpolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Separation of perhalogenated compounds resulting from thermolysis, photolysis or radiolysis of mixtures of halogens in carbon tetrachloride was carried out by programmed temperature gas chromatography. Plots of relative retentions (to CBr4) vs the number of bromine atoms present for known compounds of the general formula CxBryClz (x=1 and 2; y+z=4 or 6) gave three linear correlations (all with r〉0.99). These correlations permitted projections of the identities of reaction products for which no standards were available. These projections were later confirmed by CG-MS. *** DIRECT SUPPORT *** A0732166 00010
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  • 20
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    Chromatographia 26 (1988), S. 413-416 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas analysis in incandescent lamps ; Gas chromatographic determination of O2 impurity in argon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive GC method was developed to analyse O2 (∼10–400ppm) in argon, by using Ar as carrier gas. A sampling method was developed for lamp analysis, and the O2 impurity content in the gas filling of incandescent lamps was measured. The results of the GC and MS measurements were in good agreement.
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  • 21
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 1 (1988), S. 115-117 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel oxygen induced reduction of α,β-unsaturated carbonyl compounds is discovered. The reduction of the carbon-carbon double bond of α,β-unsaturated carbonyl compounds by benzeneselenol was caused by an introduction of molecular oxygen into the reaction system. This reduction is likely to proceed via a radical chain pathway involving an SH2 type reaction between a phenylseleno radical and a 1,2-adduct of benzeneselenol to the carbonyl group of the α,β-unsaturated carbonyl compound to give an allylic radical which absracts a hydrogen atom from benzeneselenol to form the reduction product.
    Additional Material: 1 Tab.
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  • 22
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 1 (1988), S. 191-195 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photochemical reaction of MAQO with various aromatic amines were studied by ESR. The results show that nitroxide radicals are stable productrs of the photooxidation of both diphenylamines and phenylamines. The photolyzed phenothiazine does not yield nitroxide as the final product, instead it gives the neutral radical as the stable final product.
    Additional Material: 4 Ill.
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  • 23
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 1 (1988), S. 333-349 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New series of platinum complexes of cyclopropenylidenes of the types of PtX2(CP)2 and trans-PtX(PBu3)2(CP) have been synthesized, where CP is di-t-butylcyclopropenylidene (BCP) or bis(diisopropylamino)cyclopropenylidene (ACP). The 13C-NMR chemical shifts, and 13C-195Pt coupling constants (1JPtC) for the complexes are discussed in comparison with those values derived from closely related series of compounds, trans-PtCl(PR3)2L; L — —CH3, —C6H5 and —C≡CBu-t. An excellent linear relationship through the origin was obtained between 1JPtC and the formal ‘s’ % character of the carbon directly bonded to Pt for the series trans-PtCl(PR3)2L in which the Pt—C bond is regarded as a pure σ-linkage, whereas 1JPtC deviates largely from this relationship when pπ—dπ bonding interaction possibly exists in the Pt—C bond. The NMR data suggest the strong nmr trans-influence of the cyclopropenylidenes and that in the Pt—CP bond the σ-interaction is appreciable but the π-interaction is negligible.
    Additional Material: 3 Ill.
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  • 24
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 1 (1988) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 25
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 1 (1988), S. 123-131 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photolysis of N-alkyl-N-(3-aryl-3-butenyl) ureas (1) in acetonitrile gave cyclization products, 3-aryl-3-methyl-pyrrolidines, in good yields, whereas irradiation of 1 in methanol afforded methanol adducts as well as the cyclization products. Both the reactions are singlet reactions, and the cyclization is presumed to proceed via 1,6-hydrogen transfer from exciplexes with charge transfer character.
    Additional Material: 2 Tab.
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  • 26
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    Journal of Physical Organic Chemistry 1 (1988), S. 143-151 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependence of the catalytic efficiencies of sodium carboxymethylamylose (NaCMA) for the hydrolysis of N-lauryl-3-acetoxypyridinium iodide (1) and p-nitrophenyl dodecanoate (3) on its degree of substitution (D. S. = 0·00, 0·12, 0·18, 0·24, 0·29 and 0·35) and on the pH values of the solutions (pH = 7·32, 7·80, 8·10 and 9·30) have been studied. At fixed D. S. values, the observed hydrolysis rates of 1 and 3 increase with increasing concentrations of NaCMA and follow saturation kinetics. At fixed concentration of NaCMA, the rates increase with decreasing D. S. values until they reach maxima at D. S. = 0·00. Furthermore, at any D. S. value the catalytic efficiency increases with increasing pH values of the solutions. All these results indicate that the hydroxyl groups are actually the principal catalyzing groups.
    Additional Material: 5 Ill.
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  • 27
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 1 (1988) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 28
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    Journal of Physical Organic Chemistry 1 (1988), S. 169-178 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The development of positive charge β to silicon in a saturated five-membered ring has been studied in the cis- and trans-2-(trimethylsilyl)cyclopentyl trifluoroacetates. The cis substrate solvolyzes in 97% trifluoroethanol at 25° C about 5 times faster than the analogous six-membered ring, after correction for differences in ring strain. The trans substrate solvolyzes about 360 times more slowly than the analogous six-membered ring. These changes are in agreement with a hyperconjugative mechanism for interaction between the silyl group and the developing positive charge. The expected cosine-squared dependence of hyperconjugation on the Si—C—C—X dihedral angle suggests that the cis dihedral angle is reduced somewhat from the 60° in the six-membered ring, and the trans dihedral angle is reduced substantially from the 180° in the six-membered ring.
    Additional Material: 3 Ill.
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  • 29
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    Journal of Physical Organic Chemistry 1 (1988), S. 209-223 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The equilibrium acidities of phenylacetonitrile, and 20 of its m- and p-substituted derivatives have been measured in Me2SO solution. Their pKa′s plot linearly with those of the corresponding anilines. Combination of the pKa′s of these acids with their oxidation potentials, Eox(HA), and those of their conjugate bases, Eox(A-), provide an estimate of the acidities of the corresponding radical cations. The pKHA+ values for ArCH2CN+., where Ar is Ph, 1- and 2-naphthyl, and 9-anthryl, are -32, -18·5, -17·5, and -11, respectively, compared to 21·9, 20·85, 20·65, and 19·8 for the corresponding ArCH2CN acids. Acidities of PhCH(Me)CN+., Ph2CHCN+., 9-CN-FlH+., and 9-CN-XnH+. are -33, -35, -25, and -27, respectively, compared to 23·0, 17·5, 8·3, and 13·6 for the corresponding acids from which they were derived. The homolytic bond dissociation energies (BDEs) for the benzylic C—H bonds in these arylacetonitriles, estimated by combining pKHA with Eox(A-), fall in the range of 69 kcal/mol for 9-CN-XnH to 82 kcal/mol for PhCH2CN. For GC6H4CH2CN+. radical cations the acidities are decreased, relative to G=H, when G is an electron donor substituent and increased when G is an acceptor. The BDEs of the benzylic C—H bonds in GC6H4CH2CN are weakened by up to 4 kcal/mol by para donors and strengthened by up to 1·2 kcal/mol by m- or p-acceptors. The significance of these changes in BDEs with regard to the use of σ. scales and the ΔAOP method for estimating substituent effects on radical stabilities is discussed.
    Additional Material: 5 Ill.
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  • 30
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    Journal of Physical Organic Chemistry 1 (1988), S. 259-265 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 1-(Phenylazo)-1-(2-pyridyl)ethyl hydroperoxide, 1, 1-(phenylazo)-1-(2-furyl)ethyl hydroperoxide, 2, phenylazo(2-furyl)methyl hydroperoxide, 3, 1-(phenylazo)-1-(4-anisyl)ethyl hydroperoxide, 4, were synthesized in moderate yield by autoxidation of the phenylhydrazones in benzene. The ionic oxidation of benzyl methyl sulfide in benzene by 1-4 yielded the sulfoxide and the metastable α-azo hydroxides in essentially quantitative yield. The reaction was of the first order in α-azo hydroperoxide and sulfide, respectively. The relative reactivity series found was: 1(1.0) 〈4(1.4) 〈 phenylazo(4-anisyl)methyl hydroperoxide 5 (2·9) 〈2 (3·8) 〈 3 (9·6). α-Methyl substitution was found to slow the rate of oxygen-atom trasfer by a factor of 2 to 2.5. The low relative reactivity of 1 was opposite that expected based on electronic effects. Competitive intramolecular hydrogen bonding of the hydroperoxy proton to the pyridyl nitrogen in 1 accounted for the observed result.
    Additional Material: 2 Tab.
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  • 31
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    Journal of Physical Organic Chemistry 1 (1988), S. 281-285 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal and photochemical decompositions of 5 have been studied. Both reactions lead to CBr2 transfer in good to high yields. With the 2-pentenes as substrates, CBr2 transfer is stereospecific in the classical singlet carbene manner.
    Additional Material: 3 Tab.
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  • 32
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 1 (1988), S. 305-308 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Decomposition of the tosylhydrazone salts formed from cubyl carboxaldehyde and homocubanone, potential precursors of cubylcarbene (5) and homocubanylidene (6), leads in each case to products derived from 6. It is suggested that homocub-1(9)-ene (7) is the active ingredient in the formation of 6 from both precursors. The hydrazones formed from N-aziridylamines are useful photochemical sources of 6, and presumably other carbenes. Flash vacuum pyrolysis of the tosyl hydrazone salts and hydrazones at 600°C leads to indene.
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  • 33
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    Journal of Physical Organic Chemistry 1 (1988), S. 317-332 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Light- and heat-induced decompositions and reactions with nucleophiles of 6,6,8,8-tetramethyl-2-selena-3,4-diaza-7-oxabicyclo[3.3.0]octa- 1(5),3-diene have been studied. In contrast with the conversion to the cyclopentyne derivative (9), selenium containing intermediates (6a, 6b, and 7) were efficiently trapped using several reagents to give various kinds of organoselenium compounds. Of particular note is the isolation of a stable selenirane derivative (16) obtained by the cycloaddition of the photochemically generated selenirene intermediate (7) with furan. The character and reactivity of the intermediates are also discussed.
    Additional Material: 3 Tab.
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  • 34
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    Journal of Physical Organic Chemistry 1 (1988), S. 359-362 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reaction rates for solvolysis of a mustard analogue are accurately correlated by the solvatochromic equation without inclusion of a nucleophilicity term, and thus the equation is shown to reveal mechanistically significant information.
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  • 35
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 1 (1988) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 36
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    Journal of Physical Organic Chemistry 1 (1988), S. 247-257 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rate of hydrolysis of the aromatic vinyl ether o-carboxy-α-methoxy-β,β-dimethylstyrene was found to be accelerated 25-fold by ionization of its carboxylic acid group, but the effective molarity which may be calculated if all of this rate acceleration is ascribed to intramolecular general acid catalysis is only EM = 1 · 1 m. This is similar to the small effective molarities found before for intramolecular catalysis by carboxylic acid groups of aliphatic vinyl ethers, which shows that, unlike the situation in other intramolecular reactions, e.g. ketone enolization, the extra rigidity of aromatic over aliphatic systems does not improve the efficiency of intramolecular catalysis in vinyl ether hydrolysis.It is suggested that this behaviour is the result of reduced conjugation between the vinyl ether group and the aromatic ring in the transition state of the vinyl ether hydrolysis reaction, which retards the rate and offsets any improvement effected by increased rigidity of the aromatic system.
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  • 37
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 2,2′-Diselenocyanato-1,1′-binaphthyl(1), the first selenium-containing binaphthyl derivative, has been synthesized in optically active form the corresponding diamine by diazotization followed by the reaction with potassium selenocyanate. Its molecular structure is determined by X-ray diffraction method. It is revealed that selenium atoms have hypervalent penta-coordination in the crystal.
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  • 38
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    Journal of Physical Organic Chemistry 1 (1988), S. 287-298 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ab initio STO-3G and 6-31G minimized geometries of 5-oxo- (9), 6-oxo-7-oxabicyclo[2.2.1]hept-2-yl cation (12) and 7-oxabicyclo[2.2.1]hept-2-yl cation (15) were obtained. The energy barriers for their Wagner-Meerwein rearrangements to the more stable 5-oxo- (11), 6-oxo-3-oxabicyclo[2.2.1]hept-2-yl (13) and 3-oxabicyclo[2.2.1]hept-2-yl (17) cations, respectively, have been evaluated and compared with those calculated for the rearrangement of the 5-oxo (18) and 6-oxobicyclo[2.2.1]hept-2-yl cations (20). In agreement with experimental data, the ‘true migratory aptitude’ of an acyl group is higher than that of β-oxoalkyl group in competitive Wagner-Meerwein rearrangments that are ‘energetically unbiased’. The ease of the acyl group 1,2-shift toward an electron-deficient center is related to the electron-donating ability of the carbonyl group due to favorable n(CO) ↔ σ σ ↔ p(C+) hyperconjugative interaction.
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  • 39
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    Journal of Physical Organic Chemistry 1 (1988), S. 299-303 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Iodide ion promotes the free radical reaction of isopropylmercury idide with bromotrichloromethane to yield isopropyl bromide with rate enhancement in the order of 104. The reaction involves electron transfer from i-PrHgI2- to the trichloromethyl radical in a long kinetic chain process. Iodide ion also promotes the free radical chain conjugate addition of tert-butylmercury chloride to α,β-unsaturated ketones, esters, phosphonate esters and sulfones. Competitive reactivity studies indicate that lithium di-tert-butylcuprates or tri-tert-butylzincates react with 2-cycloalkenones by a mechanism involving attack by tert-butyl radicals. No evidence for radical attack is observed for the corresponding n-butyl ate complexes of copper or zinc.
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  • 40
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    Journal of Physical Organic Chemistry 1 (1988), S. 103-114 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of solvent additives on the course of TiO2 photocatalyzed oxygenation of α-methylstyrene has been studied. While the addition of small amounts of nonhalogenated alcohols to TiO2 powders suspended in acetonitrile was found to decrease the rate of photooxygenation, added halogenated alcohols increase the rate of reaction. In addition, the solvent additives affect the observed product distribution.
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  • 41
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    Journal of Physical Organic Chemistry 1 (1988), S. 119-121 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reduction of aromatic aldehydes by benzeneselenol is found to be promoted by molecular oxygen to give corresponding alcohols in good yields. No reduction took place without oxygen.A free radical process involving SH2 reaction at the selenium atom is proposed where the phenylseleno radical attacks the selenium atom of selenohemiacetal, the adduct of benzeneselenol to aldehyde, to give the ketyl radical which then abstracts hydrogen from benzeneselenol. The intermediacy of selenohemiacetal is supported by a quantitative reduction of α-methoxybenzyl phenyl selenide, which is used as a model compound of the intermediate.
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  • 42
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependency of the wrapping-up capability of sodium carboxymethylamylose (NaCMA) on its degree of substitution (D. S. = 0·00, 0·12, 0·18, 0·24, 0·29, 0·35 and 0·41) have been studied, using two guest species, iodine and cetyl-trimethylammonium bromide (CTAB). The λmax values of NaCMA-iodine helical inclusion complexes decrease with increasing D. S. values and the amounts of encapsulated iodine by NaCMA as measured by amperometric titrations also decrease with increasing D. S. values. With CTAB as the substrate, the largest number of binding sites, n, and the dissociation constants Kd have been determined by the method of surface tension versus the CTAB concentration plots. The results show that n decreases while Kd increases with increasing D. S. values. All these observations point to the fact that the wrapping-up capability of NaCMA decreases with increasing degrees of substitution. The results are discussed in terms of host-guest and host-solvent hydrophobic-lipophilic interactions as well as intramolecular hydrogen-bonding.
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  • 43
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    Journal of Physical Organic Chemistry 1 (1988), S. 161-167 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The temperature-dependence of the kinetic isotope effects for branched reactions proceeding via a common intermediate has been simulated by calculations. It is shown that, under certain conditions, anomalously small isotope effects on the Arrhenius preexponential factors, as well as unusually large observed isotope effects, may originate from the branching.
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  • 44
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    Journal of Physical Organic Chemistry 1 (1988), S. 153-160 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structures of the allyl anion (1) and two fluoro-substituted derivatives, perfluoro (2) and 1,1-difluoro (3) have been calculated by ab inito molecular orbital theory. Geometries were gradient optimized, and force fields and an MP-2 correlation correction were determined at stationary points. The calculations were done with a double zeta basis set augmented by d functions on carbon (DZ + Dc). Final self-consistent field (SCF) and MP-2 energy calculations were done with the DZ + Dc basis set augmented by diffuse functions. The ground state of 1 is the planar allyl anion (C2v). The rotation barrier in 1 is 21·1 kcal/mol at the MP-2 level. The cyclopropyl carbanion is 27·0 kcal/mol higher in energy at the MP-2 level. The perfluoroallyl anion is not planar, and the rotated structure is 25·7 kcal/mol more stable than the C2v structure at the MP-2 level. The lowest energy structure on the potential energy surface for 2 is the perfluorocyclopropyl carbanion which is 27·8 kcal/mol more stable than the C2v structure at the MP-2 level. The 1,1-difluoroallyl anion is also not planar. Here the most stable structure on the potential energy surface is the rotated allyl anion which is 8·3 kcal/mol more stable than the all-planar allyl anion structure.
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  • 45
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    Journal of Physical Organic Chemistry 1 (1988), S. 241-245 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rates of solvolysis of l-aryl-l-phenyl-2,2-dimethylpropyl(1) p-nitrobenzoates and of aryldiphenylmethyl-p-nitrobenzoates (2) were measured in 80% acetone. An inverse order of reactivity, kp-CF3/km- CF3 〉 l was observed for 1 but not for 2. The X-ray crystallogoraphic study of the parent compounds, l,l-diphenyl-2,2-dimethylpropyl-p-nitrobenzoate (1b) and triphenylemethyl benzoate (3b), and of 2-phenyl-2-propyl-p-nitrobenzoate (4) indicated that in the highly congested system 1 both phenyl rings were nonplanar, whereas the phenyl rings in 3 and 4 were essentially planar.
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  • 46
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    Journal of Physical Organic Chemistry 1 (1988), S. 185-190 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: From the 1H-NMR spectra of the various pyrrole compounds, 1-substituted 2,5-dimethylpyrroles having two substituent groups on the carbon adjacent to the nitrogen atom were found to be very much hindered compounds. 1-[(1-Substituted)-2-phenylethyl]-2,5-dimethylpyrroles showed the restricted rotation, and the phenyl group of the most stable conformer was in close proximity to the pyrrole group due to dipole interaction. These NMR observations were supported by force field conformational analysis.
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  • 47
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    Journal of Physical Organic Chemistry 1 (1988), S. 197-207 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ESR spectra of l-cyano-2-(trimethylsilyl)ethyl and related radicals were recorded. Temperature dependent ESR spectra of these radicals revealed that electron-releasing trimethylsilylmethyl and electron-withdrawing cyano groups synergetically functioned to stabilize the radical centers due to σ-π captodative effects.
    Additional Material: 10 Ill.
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  • 48
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The excellent linearity (R2 = 0·997) of a plot of pKa values for 17 m- and p-substituted benzyl phenyl sulfones, GC6H4CH2SO2Ph, vs. those for the corresponding arylacetonitrile, GC6H4CH2CN, demonstrates that substituent solvation and substituent solvation assisted resonance (SSAR) effects for p-CN, p-COPh, and p-SPh are nearly identical in these two substrates. The PhSO2 group in PhCH2SO2Ph increases the BDE of the α-C—H bond by 2 kcal/mol, relative to toluene. The α-C—H bonds in GC6H4CH2SO2Ph sulfones are stabilized by 1-2 kcal/mol by acceptor G′s (m-CN, p-CN, m-CF3, p-CF3), but weakened by 1 and 5 kcal/mol, respectively, by donors (p-OMe and p-NMe2). The GC6H4CH2SO2Ph+. radical cation with G = H has a pKHA+. = -25. Its acidity is increased when G is an acceptor by as much as 9 to 10 kcal/mol (G = 3-CN, 3-CF3, 4-CF3, 4-NO2), but is decreased when G is a donor by as much as 33 kcal/mol (G = NMe2). When G = 4-SPh the radical cation is stabilized, relative to G = H, by a larger amount (25 kcal/mol) than when G = 4-OMe (18 kcal/mol). Structural changes along the series PhCH2SO2Ph, 2-naphthyl-CH2SO2Ph, 9-anthryl CH2SO2Ph cause negligible changes in the acidities of these acids, but sizable decreases in the acidities of the corresponding radical cations. Introduction of a phenylsulfonyl group into the methyl group of 9-methylanthracene or the 9-position of fluorene or xanthene increase the BDEs by 3, 2, and 7 kcal/mol, respectively. These effects of PhSO2 groups are compared and contrasted with those of CN groups.
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  • 49
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    Journal of Physical Organic Chemistry 1 (1988), S. 267-273 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The PE spectra of four stable bicyclic triaziridines with trifluoromethyl, methyl, phenyl, spirocyclopentane and spirocyclohexane substituents are measured. From a comparison of these experimental data with MNDO calculations the energies and the interactions of the nitrogen lone-pair orbitals were obtained. The trifluoromethyl group may be reliably simulated by a fluorine atom. The ionization potentials are unexpectedly high and so are the cyclovoltammetric anodic potentials. The MNDO valence electron densities are in agreement with the comparatively small differences in the chemical shifts of the differently substituted nitrogens of the triaziridine rings.
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  • 50
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    Journal of Physical Organic Chemistry 1 (1988), S. 275-280 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to examine the substituent effect of ethylenedithio and trimethylenedithio groups on electron acceptors, the two title compounds were prepared in one step from the corresponding quinones. These species behave as weak π-electron acceptors owing to the electronic and sterical effects of the fused groups. Only the bis(ethylenedithio) derivative formed a charge-transfer complex with tetrathiotetracene, which showed a moderate electric conductivity of 2·0 × 10-2 S cm-1. In addition, both species oxidized copper, sodium, and potassium iodides to give the corresponding deeply colored metal salts, most of which were semiconductive. The naphtho analogs were similarly studied, but hardly served as electron acceptors.
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  • 51
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    Journal of Physical Organic Chemistry 1 (1988) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 52
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photoresponse of the poly(vinyl chloride) membranes, which contain spirobenzopyran and crown ether, covered with a urease layer was studied in the presence and absence of urea. In the absence of urea, UV light irradiation induced more than 160 mV of membrane potential change, whereas the photoresponse decreased with an increase in the concentration of urea in the solution. The effects of such operating variables as crown loading and pH and ionic strength in the aqueous phase on the potentiometric response were also elucidated in the presence of urea. The results were explicated using the fact that the local concentration on NH4+ and H+ ions changed as a result of the urease-catalyzed decomposition reaction of urea.
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  • 53
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    Journal of Physical Organic Chemistry 1 (1988), S. 351-357 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The title reaction is an instance of a simple nucleophilic attack of neutral nitrogen on aromatic sp2 carbon. The kinetic data (obtained in dimethyl sulphoxide) are compared to the results reported by the literature for the same reaction of aliphatic amines. Some possible interactions (substrate/nucleophile, substrate/salt) preceding the attack of the nucleophile are discussed.
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  • 54
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    Journal of Physical Organic Chemistry 1 (1988), S. 21-27 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structure of radical intermediates appearing in the reactions of MeMgBr with aromatic monoketones was investigated by using ESR and visible spectroscopy. Stable radical intermediates in the reacting solutions were assigned to the dimeric radical ion pairs.
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  • 55
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    Journal of Physical Organic Chemistry 1 (1988), S. 33-38 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several Cotton effects are developed within absorption bands of trinuclear organotransitionmetal complexes in the presence of acids, diols, amines and aminoalcohols even in the case of bulky substituents on nitrogen; with monohydroxy compounds no circular dichroism could be detected.
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  • 56
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    Journal of Physical Organic Chemistry 1 (1988), S. 29-31 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Disparity reaction proposed in a recent application of Marcus-Grunwald theory to nitroalkane ionization is shown to put the reaction's transition state in an energy-diagram region where electronic rearrangement leads proton transfer, contrary to experimental evidence; it is suggested that addition of solvent reorganization to electronic rearrangement as the second reaction progress variable would remedy this situation.
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  • 57
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    Journal of Physical Organic Chemistry 1 (1988), S. 39-46 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Triethylsilyl radical was generated by laser flash photolysis of a 1:1 (v/v) solution of triethylsilane and di-tert-butyl peroxide. The silicon centered radical was reacted with sulfides to give carbon centered radicals by displacement at sulfur. The carbon radicals were readily detected by their transient absorption spectra. The absolute rate of reaction of triethylsilyl radical with 9-fluorenylphenylsulfide, di-n-butylsulfide, di-sec-butyl sulfide, di-tert-butyl sulfide and di-n-butyl disulfide are 2.40 ± 0.12 × 108 M-1S-1, 1.1 × 107±0.89×106M-1S-1, 8.79± 0.73×106M-1S-1, 3.29±0.18×106 M-1S-1, and 3.41±0.09×108 M-1S-1, respectively.
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  • 58
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    Journal of High Resolution Chromatography 11 (1988), S. 106-110 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Tandem capillaries ; Charcoal trapping ; Soil fumigants ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Soil fumigants, like 1,3-dichloropropene and metham-sodium (forming methyl isothiocyanate) diffuse into the atmosphere, thus presenting a hazard to people in the surroundings. A method is described in which a large volume (50 μl) of extractant, used to desorb the compounds from charcoal, is injected into a GC, equipped with two capillary columns. By way of Deans switching, the solvent is separated from the compounds of interest. Modification of a GC sampler makes unattended analyses possible.
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  • 59
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    Journal of High Resolution Chromatography 11 (1988), S. 218-220 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary column ; Essential oil ; Juniperus communis L ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 60
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    Journal of High Resolution Chromatography 11 (1988), S. 337-338 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Connector ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 61
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    Journal of High Resolution Chromatography 11 (1988), S. 491-495 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary columns, glass ; Superox-4, stationary phase ; Persilanization by DPTMDS ; Immobilization by DCUP ; Irganox 1010, antioxidant ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 62
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    Journal of High Resolution Chromatography 11 (1988), S. 661-663 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Mass spectrometry ; Capillary GC ; Aminonitropyrene ; Nitropyrenamine ; Nitro-PAHs ; Atmospheric pressure ionization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 63
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Environmental tobacco smoke ; Sampling ; Tenax ; Nicotine, 3-Ethenylpyridine, Particulate nicotine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A combined sampling and analysis technique for the determination of gas phase nicotine and 3-ethenylpyridine, and of particulate phase nicotine in environmental tobacco smoke with capillary gas chromatography is reported. The major advantage of the technique is that all of the collected particulate phase material is analyzed by thermal desorption of the collected material rather than by analysis of only a fraction of the sample extracted from the collection medium. A Teflon filter microtube is used to collect particulate phase nicotine. This microtube is follwed by a small Tenax sorbent bed to collect gas phase nicotine and 3-ethenylpyridine. After sampling, the Teflon filter is transferred to a clean glass tube and the tube becomes an insert for a modified packed column injector port where the material collected on the filter is heat desorbed to a cold capillary tubing trap. Gas phase nicotine and 3-ethenylpyridine are also transferred from the Tenax to the GC column by thermal desorption from the Tenax sorbent bed. Gas phase nicotine and 3-ethenylpyridine, and particulate phase nicotine are each determined by GC analysis of the desorbed material. Nicotine and 3-ethenylpyridine are quantitated by the use of external standards. This technique is straightforward and can be used for semi-real time determination of both gas and particulate phase compounds in environmental tobacco smoke. The results obtained by this technique compare well with those obtained by sampling with annular diffusion denuders.
    Additional Material: 13 Ill.
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  • 64
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    Journal of High Resolution Chromatography 11 (1988), S. 449-456 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary columns ; Micropreparative enrichment ; Volatile components ; Micro sample handling ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes a computerized system for micropreparative enrichment of components from a mixture being separated on a capillary column. All electronic components are commercially available. Programming was performed in BASIC so that users can easily adapt the program to their own special needs.The enrichment procedure is based on a repetitive absorption of eluting compounds after separation from a capillary column, by sucking them through an absorption tube mounted at the outlet splitter. In order to perform this procedure reliably, the system searches for reference peaks which can stem from componetns of the mixture or from deliberately added reference compounds. Use of error diagnostics prevents contamination of the collected fractions in case of system failures. Optimization is easily performed during a supervised GC run in a semiautomatic mode. Using the function keys of the computer, the operator can adjust injection volume, measure the base line drift at any retention time, and perform reference peak allocation and peak switching until optimal conditions have been found.The system presented has been in operation for several years in our laboratory where, in some cases, the mixture had to be injected onto the capillary column over 500 times to obtain the amount of pure component (10-1000 μg) necessary for NMR structure elucidation. However, recording of meaningful spectra of such small amounts requires special precautions in sample handling. This technique can also be applied for sample recovery after analysis by non-destructive elucidation methods or by chemical microreactions without loss.
    Additional Material: 6 Ill.
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  • 65
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    Journal of High Resolution Chromatography 11 (1988), S. 605-607 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Mass spectrometry ; Methyl p-hydroxyphenyllactate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 66
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Large diameter open tubular column ; Water analysis ; Chlorinated hydrocarbons ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 67
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Homologized series ; Retention volumes ; Family behavior ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 68
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    Journal of Physical Organic Chemistry 1 (1988), S. ii 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 69
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 1 (1988) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 70
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    Journal of Physical Organic Chemistry 1 (1988), S. 1-20 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Substrates with neutral leaving groups undergo unimolecular solvolysis in nonpolar solvents. Whereas t-alkyl substrates invariably solvolyze by a unimolecular mechanism, s-alkyl and primary alkyl substrates can undergo both uni and bimolecular reactions, and the bimolecular step can take place on either the substrate itself or on an intimate ion-molecule pair formed in either a pre-equilibrium or in a rate determining step. Study of reactions at borderlines indicates that the individual reaction types remain distinct and do not merge.
    Additional Material: 6 Ill.
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  • 71
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    Journal of High Resolution Chromatography 11 (1988), S. 51-56 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Air analysis ; Airborne halocarbons ; Chlorocarbons ; Electron capture detector ; Forest decline ; Halocarbons ; Thermodesorption ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The atmospheric levels of C1- and C2-halocarbons are determined by trapping on an adsorbent, thermodesorption, cryofocussing, gas chromatographic separation on a thick-film capillary, and electron-capture detection. The various aspects relevant to reliability and accuracy are discussed, such as type of adsorbent, range of detector response, and levels of contaminants present in blanks. These in turn have implications for optimum sample size and amount of adsorbent. The adopted method is suitable for routine analysis of airborne halocarbons at variable locations. The air concentrations of C1- and C2-halocarbons on the ground of mountain forests are similar to those in cities, a fact which supports the hypothesis that chlorocarbons are involved in the initiation of a phytotoxicological phenomenon commonly referred to as “forest decline”.
    Additional Material: 5 Ill.
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  • 72
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    Journal of High Resolution Chromatography 11 (1988), S. 73-75 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; 100 μm i.d. capillary column ; High speed separations ; Lemon oils ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Narrow bore columns (100 μm) have successfully been applied in the analysis of commercial lemon oils. On these columns, high resolution is obtained in a short analysis time. Different Brazillian lemon oils are characterized qualitatively and quantitatively.
    Additional Material: 2 Tab.
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  • 73
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    Journal of High Resolution Chromatography 11 (1988), S. 157-161 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary columns ; Immobilization ; Deactivation ; OV-1701-vinyl ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new simplified method was developed for the preparation of immobilized stationary phase fused silica capillary columns coated with OV-1-vinyl, SE-54, and OV-1701-vinyl. This methodology includes the application of the moderately polar stationary phase OV-1701-vinyl as a surface deactivation agent that may also participate in the dicumyl peroxide initiated free radical immobilization process. Practical details of the procedure are presented and applications of the laboratory-produced columns are illustrated with capillary gas chromatographic separations of standard mixtures. Possible contributions of the OV-1701-vinyl deactivation layer to both crosslinking and surface bonding in the immobilization process are discussed.
    Additional Material: 7 Ill.
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  • 74
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    Journal of High Resolution Chromatography 11 (1988), S. 162-167 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary columns ; PLOT columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A porous polymer is deposited on the inner wall of fused silica capillary columns. The retention characteristics of this porous polymer were evaluated and found to be comparable with Porapak Q. The porous polymer has a high retention volume which enables the separation of permanent gases at ambient temperatures or higher. The hydrophobic character of the porous polymer allows the injection of water containing samples without changing retention due to adsorption of water. The inertness of the porous polymer allows the elution of a range of apolar and polar compounds. The maximum temperature of the porous polymer was estimated to be 250°C. With this new type of capillary column, high resolution separations are obtained in combination with short analysis times.
    Additional Material: 11 Ill.
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  • 75
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    Journal of High Resolution Chromatography 11 (1988), S. 229-233 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Fused-silica capillary ; Wide bore glass capillary ; Packed column ; Plasma amino acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure is described in which a wide bore glass capillary column is used as an alternative to the more traditional packed column in the analysis of amino acid levels in plasma. The coefficients of variation for all amino acids (with the exception of aspartic acid) were better than 11% with recoveries ranging from 81% to 122%. The data are compared with the corresponding results obtained using a packed column and show significant differences (p 〈 0.005) between values for glycine, serine, isoleucine, proline, methionine, aspartic acid, phenylalanine, and lysine. A similar comparison between results from the wide bore and the fused-silica open tubular (FSOT) column shows better agreement. Adjustment of chromatographic conditions for the wide bore analysis yields results in good agreement with those from FSOT analysis but which still differe significantly from the backed column data.
    Additional Material: 2 Ill.
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  • 76
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    Journal of High Resolution Chromatography 11 (1988), S. 234-241 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Fused-silica capillary column ; Chlorinated hydrocarbons ; EPA Method 8120 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four mega-bore, one wide-bore, and one narrow-bore fused-silica capillary columns were evaluated for their applicability to the GC/ECD analysis of 22 chlorinated hydrocarbons, some of which are currently targeted by EPA Method 8120. No one column can resolve all 22 compounds investigated here. Four compounds (two pairs) are coeluting on the SPB-35, DB-210, DB-WAX, and DB-519 fused-silica capillary columns, five compounds (two groups) are coeluting on the DB-1301 fused-silica capillary column, and ten compounds (five pairs) are coeluting on the SPB-5 fused-silica capillary column. The analysis time varies between 30 and 50 min. The order of elution of the chlorinated benzenes seems to depend on their boiling points rather than on the polarity of the liquid phase. The retention times of an additional nine chlorinated toluenes, eight chlorinated xylenes, and five chlorinated naphthalenes are also reported. Electron capture detector linearity is reported for the DB-210 fused-silica capillary column. Five brominated compounds were investigated as possible internal standards for Method 8120.
    Additional Material: 7 Ill.
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  • 77
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    Journal of High Resolution Chromatography 11 (1988), S. 256-263 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Fused silica capillary columns ; Cyanopropyl stationary phases ; OH-terminal groups ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Due to their high polarity and unique selectivity, cyanopropyl silicones are basic stationary phases for high resolution capillary gas chromatography. Different OH-terminated cyanopropyl silicones, containing a high cyanopropyl content, were synthesized and chromatographically evaluated. Special attention was paid to the degree of immobilization of the phases in FSOT columns. Depending on the problem at hand, a choice has to be made between immobilization and maximum selectivity.
    Additional Material: 9 Ill.
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  • 78
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    Journal of High Resolution Chromatography 11 (1988), S. 271-277 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Thick film capillary columns ; Packed columns ; High pressure packed columns ; Loadability ; Open tubular columns with large diameter ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present paper compares the potential of high pressure packed column gas chromatography, with a particle size in the range of 30-80 μm and conventional packed column GC. with that of thick film capillaries for obtaining the maximum loadability at a given performance in efficiency and speed of separation. An alternative treatment, discussing the maximum efficiency of the three column types at normalized loadability and speed of separation is given. Known and established relationships describing plate height, loadability, and linear velocity are used to arrive at the said comparisons. The conclusion of the paper indicates a reconsideration of packed column GC for particular types of analyses where large amounts or high concentrations are required in the detection step.
    Additional Material: 5 Ill.
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  • 79
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    Journal of High Resolution Chromatography 11 (1988), S. 585-587 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Mass spectrometry ; Spectrum comparison ; Peak shape ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 80
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    Journal of Physical Organic Chemistry 1 (1988), S. 59-61 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Treatment of α, α′ -diketo selenides, which recently became readily obtainable, with base affords α-oxo selenoaldehydes and ketones. The seleno-carbonyl compounds thus formed are reactive transient species, but can be trapped by Diels-Alder reaction to give 3,6-dihydro-2H-selenapyran derivatives in moderate to good yields.
    Additional Material: 1 Tab.
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  • 81
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    Journal of Physical Organic Chemistry 1 (1988), S. 47-51 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This paper describes the synthesis and electrochemical behavior of dicationic salts of ethenediylidene-2,2′ -bis(1,3-dithiole) (3) and butatriene-1,4-diylidene-2,2′ -bis(1,3-dithiole) (4). These are expected as donor components for developing organic conducting and superconducting materials, on the grounds of high electron donating ability and of rigid skeletal structure with two and four cumulenic carbons inserted between two 1,3-dithioles. These salts were obtained in good overall yields by several steps starting from (2-morpholino-4,5-dimethyl or -diphenyl)-1,3-dithiolylium salt. From the 1H and 13C NMR, and electronic spectra it is suggested that the π conjugation between two 1,3-dithiolylium ions through an acetylenic bond is less effective than that through an olefinic bond of the corresponding salts of ethanediylidene-2,2′ -bis(1,3-dithiole) (1) and 2-butene-1,4-diylidene-2,2′-bis(1,3-dithiole) (2). The cyclic voltammetric study shows that the corresponding radical cations, and in particular 3 and 4, are less stable even at -40°C, thus providing reasons for our current lack of success in isolation of 3 and 4. From comparison of the first redox potentials of neutral species, it is deduced that the donating ability increases in the order of TTF 〈 1 ⋍ 2 ≲ 3 ≪ 4.
    Additional Material: 2 Ill.
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  • 82
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    Journal of Physical Organic Chemistry 1 (1988), S. 53-57 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction of sulfur ylides with elemental sulfur or selenium initially affords thio- or seleno-carbonyl compounds, which then react with starting ylides to give episulfides or episelenides from which the heteroatom (sulfur or selenium) is extruded to give olefins as the final product. In the case of carbonyl-stabilized ylides, the resulting thio- or seleno-carbonyl compounds react with starting ylides to afford 1,3-oxathioles or 1,3-oxaselenoles as previously reported. Supporting evidence for the intermediacy of thio(seleno)-carbonyl compounds and episulfides (episelenides) is presented.
    Additional Material: 1 Tab.
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  • 83
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    Journal of Physical Organic Chemistry 1 (1988) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 84
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    Journal of Physical Organic Chemistry 1 (1988), S. 63-73 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Novel structural features of 5, 15-dialkylporphyrins in solution are described. The 1H-NMR spectra of these compounds showed broad signals at room temperature, which split into two sets of signals at lower temperatures. This unusual phenomenon was ascribed to a dynamic interconversion between tow distorted structures. The 5, 15-dialkylporphyrin has a distorted ring due to the steric hindrance between the 5(or 15)-alkyl group and the 3, 7(or 13, 17)-alkyl groups and, depending on the position of the 5, 15-alkyl groups relative to the average ring plane, can exist in two conformations; syn (where the two alkyl groups are on the same side of the ring plane) and anti (on the opposite sides). Preliminary kinetic study of this interconversion using the NMR line shape analyses is also reported.
    Additional Material: 1 Ill.
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  • 85
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    Journal of Physical Organic Chemistry 1 (1988), S. 75-81 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Highly sterically demanding 2,4,6-tri-t-butylphenyllithium (1) reacts with carbon disulfide to give 1,2-dibutylthio-1,2-bis(2,4,6-tri-t-butylphenylthio) ethene (3), l-butylthio-1-(2,4,6-tri-t-butylphenylthio)pent-l-ene (4), and 2-butylthio-3-(2,4,6-tri-t-butylphenylthio)-1,3-dithiole-2-thione (5) when 1 is prepared by the reaction of 1-bromo-2,4,6-tri-t-butylbenzene with n-butyllithium. When the reaction is carried out using 1 prepared from 2 and t-butyllithium and then quenched with l-iodoethane, 2-ethylthio-3-(2,4,6-tri-butylphenylthio)-1,3-dithiole-2-thione and 1,2-diethylthio-1,2-bis(2,4,6-tri-t-butylphenylthio) ethene are produced. The formation of all these products can be explained in terms of initial thiophilic attack of 1 on the sulfur of carbon disulfide and an intermediate with a dual property of carbanion and carbene (i.e., ArSC(Li)(=S) ⇌ ArSC̈SLi) is suggested. The reaction of 1 with thiophosgene affords 1,2-dichloro-1,2-bis(2,4,6-tri-t-butylphenylthio) ethene, bis(2,4,6-tri-t-butylphenylthio)acetylene, and 1-chloro 2,4,6-tri-t-butylbenzene, the first two of which are explained to be formed by thiophilic attack of 1 with thiophosgene.
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  • 86
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    Journal of Physical Organic Chemistry 1 (1988), S. 91-102 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photolysis of benzoinalkylethers 1-5 solubilized in detergents show a significant deviation from the course of reaction in isotropic organic solvents. Remarkable difference in photobehaviour is noticed between the short chain (1-3) and the long chain (4 and 5) benzoinalkylethers in the micellar media. However, the influence of the micellar media on the photobehaviour of alkyldeoxybenzoins 6 and 7 was small. The importance of ‘cage effect’ in controlling the product distribution was evident from its dependence on the micellar size and on the occupancy number. More importantly, a comparative analysis of the photobehaviour of the ketone 1-7 reveals that the micellar interface can be used to control the conformations of organic molecules.
    Additional Material: 1 Ill.
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  • 87
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    Journal of Physical Organic Chemistry 1 (1988), S. 83-90 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Theoretical studies on the reactions of ammonia with ketene and dimethylketene using the MNDO method are reported. The single step addition of ammonia to the olefinic bond of ketenes was found to provide a lower energy-barrier path than the two step carbonyl addition mechanism. The barrier height was lower in the reaction of keten compared with that of dimethylketene in support of the faster rate of solution phase reactions of aniline and ketenes. The deformation energies of reactants had an overwhelming influence in determining the activation barriers in all the reactions investigated.
    Additional Material: 4 Ill.
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  • 88
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Simultaneous distillation-extraction ; Cheese volatiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simultaneous distillation-extraction apparatus proposed by Godefroot has been used for the GC study of volatile components of cheese. 5–10 g of cheese provide a fraction that can be directly injected into a GC or a GC/MS. Two capillary columns (SE-30 and SP-1000) were evaluated, the second one being adequate for quantitative determinations. Camphor was used as internal standard. The coefficients of variation ranged from 1.4 to 11.8. The technique can be used as a fast method for the characterization of cheeses from their volatile component concentrations.
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  • 89
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    Chromatographia 25 (1988), S. 993-998 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; HPLC system ; Micropacked column ; Organic mobile phase ; UV detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention behaviours of aromatic hydrocarbons were examined by using the vapour of an organic substance as the mobile phase and silica gel as the stationary phase. Gas chromatographic separation of aromatic hydrocarbons was demonstrated by using a system comprising a liquid chromatographic (LC) pump, a micropacked column for LC, a column oven and a UV detector.
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  • 90
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    Chromatographia 25 (1988), S. 1087-1088 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Log plot ; Homologous series
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The slope of the log plot of the adjusted retention time of a homologous series usually varies from that of the n-alkane series by no more than 2%, though with unusual interactions between the functional group and the stationary phase the difference may be as high as 7%.
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  • 91
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    Chromatographia 25 (1988), S. 87-90 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Free acids in cheese ; Tetramethylammonium hydroxide soaps ; Packed and capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid gas chromatographic method for the analysis of individual free fatty acids (FFA) in cheese has been developed. Lipds were extract from a cheese paste acidified with diethyl ether and tetramethylammonium hydroxide (TMAM) was used for converting the FFA to TMA-soaps, which are transformed to methyl esters in the chromatographic injector. The effect of lactic acid was determined. The reproducibility of the method was studied and the coefficient of variation for the total FFA was found to be 2.2%. Recovery of individual FFA was in the range 87 to 106%.
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  • 92
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phase polarity ; Polarity parameters ; Structure-retention relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The new stationary phase polarity parameters BN and BS evaluated from the concept of the electric intermolecular interactions are used to describe the polarity of polyoxyethylene glycol dialkyl ethers and their sulphur analogs. Relations between the discussed parameters and accepted measures of surfactants' polarity are presented and discussed. The considered parameters are correlated with the compound structures. Structural increments for characteristic fragments of the molecule are calculated and use to predict BN and BS values.
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  • 93
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    Chromatographia 25 (1988), S. 134-138 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sulfur ; n-Octane adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary From the adsorption isotherms of n-octane on the surface of sulfur at 29.8°C and 40.6°C some thermodynamic functions were determined. On the basis of these data the structure of the adsorbed layer of n-octane is postulated. The molecular interactions and adsorption mechanism are also discussed. It is stated that both quasi-liquid and quasi-sold layers may be formed on the surface of sulfur depending on the surface coverage with n-octane.
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  • 94
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Essential oils ; Evaporation rate ; Perfume composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple method was developed for the determination of the evaporation rate of essential oils and perfumery composition using gas chromatography with temperature programming. The volatility of 19 essential oils and 17 perfumery composition was evaluated. The method is useful for different comparative measurements.
    Type of Medium: Electronic Resource
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  • 95
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 25 (1988), S. 735-736 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; α,ω-diiodoperfluoroalkanes ; Separation ; identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of α,ω-diiodoperfluoralkanes on a glass capillary column coated with OV-101 methylsilicone was investigated. Retention indices were determined at three temperatures (140, 150 and 160°C). The correlation between the retention indices and the boiling points of the investigated compounds was studied.
    Type of Medium: Electronic Resource
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  • 96
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 26 (1988), S. 125-132 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Non-equilibrium frontal chromatography ; Nonlinear isotherms ; Variable velocity ; Multicomponent mixtures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper presents a classification of various theoretical models for multicomponent gas chromatography at u=var for high concentrations of the mixture components with consideration of the major distinctive features of the interphase mass exchange inside the porous grains of the adsorbent and outside them within the porous medium of the chromatographic column. It has been shown that the conditions determining a given front behaviour of multicomponent gas mixture at u=var depend on: theoretical models for the kinetics and dynamics of adsorption; the values of mass exchange parameters inside the porous grains and in the porous medium. Formulae have been derived for calculating the values of the quantities characterising the frontal behaviour in the stage of adsorption and desorption of multicomponent mixture at u=var.
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 330 (1988), S. 1-14 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Liquid-Crystalline Heterocycloalkanes. III. Synthesis and Liquid-Crystalline Properties of Substituted 1,3-DioxadecalinesLiquid-crystalline 2-substituted and 2,6-disubstituted 1,3-dioxadecalines (4 - 6) were synthesized by acid-catalyzed acetalization of trans-2-hydroxymethylcyclohexanol (1) or trans-4-alkyl-trans-2-hydroxymethylcyclohexanoles (2) with aldehydes 3 whereby the desired transisomers were formed only. The syntheses of the various aldehydes are also described.Special attention is drawn on the evolution of mesogenic properties of the titlecompounds 4 - 6 in comparison with known decalines and 1,3-dioxanes.It was found that the clearing temperatures of the synthesized 1,3-dioxadecalines are always lower than those of the corresponding decaline derivatives, due to the deformation of the decalineringsystem by the introduction of two oxygen-atoms. The comparison of 1,3-dioxanes and 1,3-dioxadecalines shows that the dioxadecaline ringsystem tends to suppress smectic mesophases in favour of nematics. A first example of a liquid crystalline cis-fused 1,3-dioxadecaline (8) is described, too.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 98
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 330 (1988), S. 14-14 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 330 (1988), S. 22-26 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: About the Influence of Pressure on the Catalyzed Liquid-Phase Oxidation of cis- and trans-Oct-4-eneThe investigation of the influence of pressure on the liquid-phase oxidation of cis- and trans-oct-4-ene shows that the reaction rate increases up to 491 kPa in the non-catalyzed oxidation reaction, but up to 981 kPa in the MoO2(acac)2-catalyzed reaction n-oct-1-ene reacts more slowly than cis- and trans-oct-4-ene as well in the pressure-less reaction as in the oxidation under pressure. In the non-catalyzed oxidation reaction the cis/trans- ratios don't depend on the pressure, but in the MoO2(acac)2-catalyzed oxidation reaction the cis/trans-epoxide ratios increase with increasing pressure. The optimum of the reaction temperature lies between 110 and 130°C.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 100
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,2,3-Triazabutadienes. XX. Investigations of the Photochemical Z-E-Isomerization, Photolysis, Protonation and Acidic Cleavage of 1-Aryl-3-3-methylbenzthiazolinyliden-(2)-triazenes in Micellar SolutionsThe E-isomers of the 1-Aryl-3-[3-methylbenzthiazolinyliden-(2)]-triazenes are soluble in aqueous micellar solutions of sodium dodecylsulfate (NDS) and cetyltrimethylammoniumbromide (CTAB). They are fixed in the Stern region of the micelles. The Z-isomers decompose in aqueous micellar solutions by acidic cleavage. They can be stabilized by the use of alkaline buffer solutions. The concentration of protons is higher by the factor 103 in the Stern region of NDS-micelles than in the Stern region of CTAB-micelles. This difference is explained by electrostatic attraction and repulsion between the protons and the micelles. The quantum yields of the photochemical isomerization in micellar solutions and in organic solvents are the same. Water soluble ionic dyes with relatively low triplet energies sensitize the photoisomerization in micellar solutions and the photostationary state is on the side of the E-isomer.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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