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  • Articles: DFG German National Licenses  (2,076)
  • Electronic Resource  (2,076)
  • 2000-2004
  • 1995-1999  (132)
  • 1980-1984  (1,054)
  • 1975-1979  (890)
  • 1880-1889
  • 1999  (132)
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  • Analytical Chemistry and Spectroscopy  (1,669)
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  • Articles: DFG German National Licenses  (2,076)
Material
  • Electronic Resource  (2,076)
Years
  • 2000-2004
  • 1995-1999  (132)
  • 1980-1984  (1,054)
  • 1975-1979  (890)
  • 1880-1889
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Keywords
  • 101
    Electronic Resource
    Electronic Resource
    Supercritical Fluid Extraction and Supercritical Fluid Chromatography of Vitamin E in Pharmaceutical Preparations (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 300-302 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical-fluid-extraction ; supercritical-fluid-chromatography ; vitamin E ; pharmaceuticals ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 102
    Electronic Resource
    Electronic Resource
    Teicoplanin-Based Enantiomeric Separations in CZE Using a Partial Filling Technique (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 315-321 
    Details
    ISSN: 0935-6304
    Keywords: Glycopeptide antibiotics ; chiral selectors ; Teicoplanin ; enantioseparations ; CZE ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Baseline separation of the enantiomers of a number of negatively charged amino and mandelic acid derivatives was achieved in less than 10 min by capillary electrophoresis in a polyacrylamide coated capillary, using the “partial filling method” (PFM) with submillimolar concentration of Teicoplanin (TE) as the chiral selector. The influence of the charge and concentration of TE, electrolyte solution composition and pH, on the enantioresolution was examined. Further proofs were brought to corroborate the hypothesis that the enantiorecognition takes place at the D-Ala-D-Ala binding site, whose blockade is responsible for the antibacterial activity of glycopeptide antibiotics. While the dependence of the chiral recognition capabilities of TE on electrolyte solution composition and pH could limit its applicability, improved sensitivity, reduction of TE wall adsorption, resulting in a good efficiency, and high cost reduction, due to the very small amount of chiral selector required, were shown as advantages of the PFM adopted in this study.
    Additional Material: 6 Ill.
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    Paper (German National Licenses)
  • 103
    Electronic Resource
    Electronic Resource
    Solvent Trapping during Large Volume Injection with an Early Vapor Exit. Part 3: The Main Cause of Volatile Component Loss during Partially Concurrent Evaporation (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 327-334 
    Details
    ISSN: 0935-6304
    Keywords: Large volume on-column injection ; partially concurrent solvent evaporation ; solvent trapping ; retaining precolumn ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---When 0.53 mm i.d. uncoated precolumns connected to a solvent vapor exit are used for sample introduction with partially concurrent solvent evaporation, substantial losses of volatile solutes are often observed. They were found to be the consequence of solute accumulation at the front end of the flooded zone, which in turn is the result of a strong pressure drop over the flooded zone owing to the formation of plugs of sample liquid. The pressure drop causes significant solvent evaporation at the front, which enriches the solute material there and causes its loss. The use of 0.32 mm i.d. restrictions between the uncoated precolumn and the vapor exit greatly reduced this problem.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 104
    Electronic Resource
    Electronic Resource
    Separation of Chlorophylls and Their Degradation Products using Packed Column Supercritical Fluid Chromatography (SFC) (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 339-342 
    Details
    ISSN: 0935-6304
    Keywords: Chlorophyll ; SFC ; supercritical fluid chromatography ; vegetables ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Complex mixtures of chlorophyll degradation products may arise during processing and storage of vegetable oil and green plant materials like broccoli and spinach. Determination of these compounds is important in the area of food chemistry. Therefore a method using packed column supercritical fluid chromatography (SFC) has been developed. The method comprises chromatography using a simple gradient of methanol in carbon dioxide at constant column back pressure of 30 MPa and a column temperature of 40°C. Effects of pressure and mobile phase composition showed the importance of applying a modifier gradient for optimal separation of the chlorophyll products. The method permits separation of 15 chlorophyll derivatives including chlorophyll a and b, pheophytins, and pyropheophytins on a C18 column in about 20 minutes. Identifications of the individual peaks were based on reference compounds, the retention order of the compounds, and their absorption spectra.
    Additional Material: 5 Ill.
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    Paper (German National Licenses)
  • 105
    Electronic Resource
    Electronic Resource
    HRGC/FID and HRGC/MSD Analysis of the Secondary Metabolites Obtained by Different Extraction Methods from Lepechinia schiedeana, and in Vitro Evaluation of Its Antioxidant Activity (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 343-349 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; gas chromatography-mass spectrometry ; essential oil analysis ; Lepechinia schiedeana ; antioxidant activity ; lipid peroxidation ; Ledol; Ledol HMQC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Steam distillation (SD), simultaneous distillation-solvent extraction (SDE), microwave-assisted solvent extraction (MWE), and supercritical (CO2) extraction (SFE) were used to isolate secondary metabolites from Lepechinia schiedeana. The various extracts were analyzed by capillary gas-chromatography, on poly (dimethylsiloxane) (DB-1) and poly(ethyleneglycol) (INNOWAX), 60 m columns, using FID or MSD (EI, 70 eV). Kováts indexes, mass spectra, or standard compounds were employed for compound identification. 43, 61, 67, and 79 compounds at concentrations above 0.01% were detected in the SD, SDE, MWE, and SFE extracts, respectively. Ledol, C15H26O, was the major constituent (20.04-36.87%) in all extracts. Oxygenated sesquiterpenes (24.36-43.14%), C10H16, monoterpenes (27.70-39.87%), and C15H24, sesquiterpenes (10.04-22.22%) were the main groups of compounds present in SD, SDE, MWE, and SFE extracts. Heavy hydrocarbons (Cn 〉 15), diterpenoids, and phytosterols were found only in MWE and SFE extracts. The antioxidant activity of Lepechinia schiedeana was measured by the HRGC quantification of the volatile carbonyl compounds, final products of lipoxidation, released in a model lipid system (sunflower oil) by the effect of the Fenton reagent. The concentration of volatile carbonyl compounds decreased by 65% when lipid oxidation was induced in the presence of macerated Lepechinia plant. The protection of polyunsaturated acids in sunflower oil was also studied by measuring their concentrations after heating of the oil (180°C, 2 h) with and without macerated Lepechinia plant.
    Additional Material: 4 Ill.
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    Paper (German National Licenses)
  • 106
    Electronic Resource
    Electronic Resource
    Use of Isopropanol as a Modifier in a Hexane-Acetonitrile Based Mobile Phase for the Silver Ion HPLC Separation of Positional Isomers of Triacylglycerols Containing Long Chain Polyunsaturated Fatty Acids (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 357-361 
    Details
    ISSN: 0935-6304
    Keywords: Silver ion HPLC ; long chain polyunsaturated fatty acid ; isopropanol ; separation of positional isomers ; degree of unsaturation ; normal phase retention effect ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A high resolution approach to silver ion HPLC was studied for the separation of positional isomers of triacylglycerols (TAGs) containing long chain polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and docosapentaenoic acid (DPA) in enzymatically synthesized structured TAGs. Isopropanol was used as a novel modifier in a hexane-acetonitrile based mobile phase for silver ion HPLC. Peak identification was based on HPLC-mass spectroscopy and selectivities of lipases. Positional isomers of TAGs containing one molecule of EPA, DHA, or DPA with saturated fatty acids (FAs) such as caprylic acid and palmitic acid were separated within 13 min using a gradient of hexane-isopropanol-acetonitrile as mobile phase. TAGs containing two or more EPA, DHA, or DPA were also separated from each other within 25 min, but their positional isomers were unresolved. The retention characteristics of the TAG were found to be related to the number of carbon atoms in the FAs present in addition to the number of double bonds and their isomeric configuration. One isomer with an unsaturated FA in the sn-2 position eluted faster than the other with the unsaturated FA in the sn-1 or 3 position. Species with longer chain FAs attached to TAGs with the same degree of unsaturation eluted faster than those that have shorter chain FAs. For example, docosapentaenoylhexadecanoyloctanoin (DPA/C16/C8) was eluted faster than dioctanoyldocosapentaenoin (DPA/C8/C8).
    Additional Material: 2 Ill.
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  • 107
    Electronic Resource
    Electronic Resource
    A Computer Method for Predicting the Electrophoretic Mobility of Peptides (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 373-378 
    Details
    ISSN: 0935-6304
    Keywords: Electrophoresis ; electrophoretic mobilities ; CZE ; MEKC ; peptides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A computer model is presented for the prediction of the electrophoretic mobilities of peptides from physical constants derived from their amino acid sequences. The model assumes that the electrophoretic mobility can be represented by a product of four functions according to the relation:  lcomp= l(L)w(W)q(Q)c(CC), where L (a length parameter) is represented by the number of amino acid residues of the peptide, W (a width parameter) is represented by the average residue mass, Q = the charge of the peptide, and CC = the position of the center of charge relative to the center of mass. The model was used to calculate the electrophoretic mobilities of peptides in a 50 mM phosphate buffer at pH 2.5. Sixty-four test peptides ranging in size from 2 to 39 amino acid residues were used for this study. The calculated mobilities show excellent correlation with experimental measurements with a correlation coefficient greater than 0.98.
    Additional Material: 5 Tab.
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  • 108
    Electronic Resource
    Electronic Resource
    Simultaneous Measurement of Hydrocarbons and Sulfur Compounds using Flame Ionization and Sulfur Chemiluminescence Detection for Sulfur Simulated Distillation (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 386-390 
    Details
    ISSN: 0935-6304
    Keywords: Sulfur chemiluminescence detection ; sulfur simulated distillation ; boiling point distribution ; simultaneous FID/SCD analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A gas chromatographic system for the simultaneous acquisition of hydrocarbon and sulfur chromatograms was developed. Detection of sulfur compounds is achieved using a sulfur chemiluminescence detector (SCD) mounted in series with a flame ionization detector (FID). A constant fraction of the effluent of the FID is transferred to the SCD by means of a fixed restrictor. Unlike previous versions of this approach, the FID is not used to generate the chemiluminescent sulfur species. Rather, the FID is operated under optimum conditions for hydrocarbon analysis and a furnace is used to generate the chemiluminescent sulfur species. The system permits dual acquisition of the hydrocarbon and sulfur signals in a single analysis with a single column, since the detectors are operated in a serial fashion. The application of sulfur simulated distillation using this approach was examined, since this requires simultaneous universal and sulfur selective detection. Precision of absolute response of both the FID and SCD was typically less than 2% RSD for a standard reference material.
    Additional Material: 3 Ill.
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  • 109
    Electronic Resource
    Electronic Resource
    A Novel Interface for Optimized Coupling of Gas Chromatography and Supersonic Jet Spectroscopy (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 391-394 
    Details
    ISSN: 0935-6304
    Keywords: REMPI-TOFMS ; laser mass spectrometry ; supersonic jet ; GC-MS ; interface ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The laser-based methods Laser Induced Fluorescence (LIF) and Resonance-Enhanced Multi-Photon Ionization (REMPI) can be used as highly selective detection modes for gas chromatography (GC). One major prerequisite for successful application of these detection methods is the availability of appropriate and reliable interfaces between the GC effluent and the molecular beam inlet. When a pulsed supersonic molecular beam (jet) source is used, the analyte molecules are efficiently cooled, allowing maximum selectivity of the laser spectroscopic detection methods. However, several technical problems have to be solved for practical realization of a GC-supersonic jet valve hyphenation. The pulsed jet interface should not interfere with the GC properties and the supersonic molecular beam properties. Further a good working cycle for the conversion from the continuously flowing GC current to the pulsed jet gas flow should be attained. This paper presents a novel setup of a GC-pulsed jet interface. The construction allows temporal and spatial compression of the analyte molecules in jet gas pulse and thus an increase of the detection sensitivity. Moreover, the GC effluent comes into contact only with glass surfaces and not with valve parts like plungers and seals. This reduces memory effects and sample decomposition. The valve setup is tested with a REMPI-TOFMS instrument.
    Additional Material: 2 Ill.
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  • 110
    Electronic Resource
    Electronic Resource
    Selective Determination of Se4+ and Se6+ Using SPME and GC/MS (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 414-416 
    Details
    ISSN: 0935-6304
    Keywords: Selenium ; water ; SPME ; GC/MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A method for the selective determination of Se4+ and Se6+ using solid phase microextraction (SPME) and GC/MS analysis is presented. Se4+ is selectively derivatized by reaction with 4,5-dichloro-1,2-phenylenediamine to form the corresponding piazselenolo complex, extracted by the SPME fiber, and determined by GC/MS. The RSD at a 5 μg/L concentration was 9.88% and the theoretical detection limit 6 ng/L. The method was employed to test real matrices; tap and river water were analyzed before and after spiking giving a recovery rate of 102% in river water and 97% in tap water.
    Additional Material: 3 Ill.
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  • 111
    Electronic Resource
    Electronic Resource
    Determination of Vapor Liquid Equilibrium from the Kovats Retention Index on Dimethylsilicone using the Wilson Mixing Model (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 565-588 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Kovats retention index ; vapor pressure ; boiling point ; Wilson activity coefficient ; binary phase diagrams ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Non-ideal mixing in a dimethylsilicone stationary phase is modeled according to the Wilson activity coefficient. Pure liquid vapor pressures of alkylated compound series are calculated from capillary GLC retention with the functional group heat of solution in a polymer solvent. The new method uses the Kovats index, molar mass, and functional group to determine the bubble line of a compound. Boiling points at reduced and normal pressure are compared to literature values of 194 gasoline components. An unlike molecular pair interaction parameter is derived, using only bubble line data of the pure liquids. Binary phase diagrams are constructed and compared to vapor liquid equilibrium data.
    Additional Material: 22 Ill.
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  • 112
    Electronic Resource
    Electronic Resource
    A Strategy for the Simplification and Solution of Complex Chromatographic Analysis Problems Utilizing Two-Dimensional Mapping of Retention Indexes Followed by Computer Modeling of Heart Cuts from Serially Coupled Columns Containing Different Stationary Phases (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 589-593 
    Details
    ISSN: 0935-6304
    Keywords: Computer modeling of GC ; computer simulation of GC ; computer-assisted GC analysis ; GC multicolumn analysis ; heart cutting GC analysis ; computer-assisted column design ; computer-assisted selectivity tuning ; retention index mapping ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The analysis of four components in a mixture containing many possible interferents is simplified by heart-cutting serially connected columns containing stationary phases of widely different polarities. The design of the proper lengths of the two columns and timing the heart-cuts is accomplished with the aid of a computer simulation of the problem. The computer program calculates the proper lengths of column to produce the shortest analysis time and also outputs the predicted chromatograms from both columns. The chromatogram from the first column is used to construct the timing gates for the heart-cuts and the chromatogram from the second or analytical column is used to set integration gates for the selected compounds of interest.
    Additional Material: 7 Ill.
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  • 113
    Electronic Resource
    Electronic Resource
    Indirect Fluorimetric Detection of Cyclodextrins via Postcolumn Mixing with 2-p-Toluidinyl-6-naphthalenesulfonate in Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 609-612 
    Details
    ISSN: 0935-6304
    Keywords: Cyclodextrins ; 2-p-toluidinyl-6-naphthalenesulfonate ; indirect fluorimetric detection ; liquid chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Cyclodextrins (CD's) were visualized by postcolumn mixing with 2-p-toluidinylnaphthalene sulfonate (TNS) in liquid chromatography. The indirect detection is based on fluorescence enhancement due to the formation of an inclusion complex between TNS and CD's. β-CD gave larger signal intensity than α- and γ-CD. Different selectivities were observed for alkyl-bonded silica stationary phases with different chain length.
    Additional Material: 7 Ill.
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  • 114
    Electronic Resource
    Electronic Resource
    Analysis of Methylcitric Acid by Enantioselective Multidimensional Gas Chromatography-Mass Spectrometry (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 604-608 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS) ; methylcitric acid (MCA) ; inherited metabolic disease ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Methylcitric acid (2-hydroxybutane-1,2,3-tricarboxylic acid-MCA) is a structural analogue of citric acid, but due to an additional methyl group it is a chiral molecule with two stereogenic centers and thus four stereoisomers are conceivable. MCA occurs naturally as prominent metabolite in body fluids of patients with inherited metabolic diseases such as propionic acidemia, methylmalonic aciduria, or holocarboxylase synthetase deficiency. Therefore methylcitric acid is considered to be an important diagnostic marker for these diseases. MCA is most likely produced from accumulated propionyl-CoA in these diseases by the enzyme si-citrate synthase from the citric acid cycle; however, there are other enzymes known which could catalyze the same reaction with different stereoselectivity, such as re-citrate synthase or the more specific enzyme methylcitrate synthase, found in microorganisms. Almost all methods dealing with MCA in the literature are non-enantioselective. For that reason there is no information about occurrence of MCA enantiomers in healthy people, patients with propionic acidemia, methylmalonic aciduria, or holocarboxylase synthetase deficiency and about value of enantiomeric distribution for diagnosis and long-term treatment. The enantioselective analysis of MCA as corresponding trimethyl ester was achieved by enantioselective multidimensional gas chromatography coupled with mass spectrometry using heptakis-(2,3-di-O-methyl-6-O-tert-butyl-dimethylsilyl)-β-cyclodextrin as chiral stationary phase. The described method allows a reliable screening of MCA in complex matrices like urine without time consuming sample preparation and with mass selective detection. During this investigation urine samples from various patients and healthy controls were analyzed. As concluded, MCA is a good diagnostic marker and can be easily measured by the method presented. Only the two stereoisomers (2S,3R) and (2S,3S) were detectable in patients and healthy controls. The varying ratios of these stereoisomers cannot presently be correlated with the health status of patients, although there are some indications that this might be possible. However, the quantitative levels of MCA, determined as the ratio of MCA absolute peak area divided by 1,000 to the creatinine contents of urine samples in this investigation, showed a dependence on the state of health and MCA would thus also be a possible marker for long-term treatment. Such a substance is of major interest nowadays since there are different studies searching for such a long-term marker in propionic acidemia or methylmalonic aciduria.
    Additional Material: 4 Ill.
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  • 115
    Electronic Resource
    Electronic Resource
    Relative Recoveries of Hydrocarbons from Geological Samples Using High Temperature Supercritical Fluid Extraction: Contributions from Thermal Desorption (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 623-627 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction ; hydrocarbons ; high temperature ; thermal desorption ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extraction of n-alkanes, polyaromatic hydrocarbons (naphthalene, methylated naphthalenes, phenanthrene, methylated phenanthrenes, anthracene, and methylated anthracenes) and biomarkers (hopanes) from Posidonia shale by high temperature supercritical fluid (HT-SFE) carbon dioxide extraction has been evaluated, including the relative contributions from thermal desorption and relative comparisons to conventional Soxhlet extraction. These current results confirm those of previous studies indicating a widely differing extractability of strongly and weakly associated hydrocarbons in ancient sediments and the significantly higher recoveries possible using HT-SFE compared to conventional Soxhlet extraction. The present study also demonstrates that these high HT-SFE recoveries are due to true extraction rather than simple thermal desorption and that this procedure is a useful tool to study speciation as well as total extractable hydrocarbons from sediments.
    Additional Material: 2 Ill.
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  • 116
    Electronic Resource
    Electronic Resource
    Stereoisomeric Flavor Compounds LXXXII Dill Ether and Its Stereoisomers: Synthesis and Enantioselective Analysis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 631-634 
    Details
    ISSN: 0935-6304
    Keywords: Dill ether ; stereoselective synthesis ; dill ether stereoisomers ; enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC/MS) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 117
    Electronic Resource
    Electronic Resource
    Complete Separation of Isomeric Penta- and Hexachloronaphthalenes by Capillary Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 639-643 
    Details
    ISSN: 0935-6304
    Keywords: Cyclodextrin ; Halowax ; hexachloronaphthalene ; PCN ; polychlorinated naphthalenes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 118
    Electronic Resource
    Electronic Resource
    Theory of Fast Capillary Gas Chromatography Part 4: Column Performance vs.Liquid Film Thickness (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 501-508 
    Details
    ISSN: 0935-6304
    Keywords: Fast GC ; film inefficiency factor ; high pressure drop ; thick film columns ; thin film columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The negative effect of the liquid stationary phase film thickness on the column efficiency is strongest for peaks with retention factors, k, in the vicinity of k = 0.3-0.4 and rapidly diminishes with the departure of k from that region. Additionally, at the high pressure drop required for fast analysis of complex mixtures, the negative effect of the same film thickness diminishes with the increase in column length, regardless of the k values. In practice, it is recommended to ignore the film thickness and optimize the columns as thin film ones regardless of their actual film thickness. Accounting for the film thickness results only in a modest improvement in the resolution for a few affected peaks - those with k = 0.3-0.4. However, this improvement comes at the cost of a substantial increase in analysis time, and should be used only as the action of the last resort.
    Additional Material: 4 Ill.
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  • 119
    Electronic Resource
    Electronic Resource
    Isolation and Characterization of Wax Esters in Fennel and Caraway Seed Oils by SPE-GC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 514-520 
    Details
    ISSN: 0935-6304
    Keywords: Solid-phase extraction ; high temperature - gas chromatography ; gas chromatography - mass spectrometry ; wax esters fennel seed oil ; caraway seed oil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A rapid method for the isolation and quantitative determination of wax esters in vegetable oils was developed. For the first time wax esters in oils were separated from the triglyceride matrix by means of solid-phase extraction, which allows rapid sample preparation in parallel and therefore a high sample throughput. The thus obtained wax ester fractions of fennel and caraway seed oils were analyzed by high temperature gas chromatography. GC-MS analyses were carried out using electron impact ionization in order to characterize the wax ester fraction. With respect to the results of the GC-MS analyses different isomers of saturated wax esters with the same carbon number were observed. Additional monounsaturated wax esters with an unsaturated fatty acid moiety were identified.
    Additional Material: 4 Ill.
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  • 120
    Electronic Resource
    Electronic Resource
    Comparative Methodology for Isolation of Flavonoid Glycosides from Clusia criuva Cambess (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 527-530 
    Details
    ISSN: 0935-6304
    Keywords: Clusia criuva Cambess ; counter-current chromatography ; flavonoids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The family Guttiferae belongs to the superorder Theiflorae, order Theales and according to Dahlgren's system of classification, it is equivalent to Hypericaceae (=Clusiaceae) [1]. This family consists of 49 genera encompassing over 1000 species of wide distribution in the tropics as shrubs and trees [2]. Plants of the genus Clusia have been used in folk medicine for the treatment of different kind of illness such as: febrifuge, anti rheumatic, purgative, for stomach problems and, in Brazil, they are very commonly used to heal wounds [3]. The key of any study of material from natural sources is the availability of suitable separation methods for the isolation of pure products [4-6]. Tentatives for separations using chomatography on solid support phases were not very efficients in the fractionation of Clusia criuva Cambess methanolic/ethyl acetate extracts. However, the use of counter-current chromatography, an all liquid technique, showed advantages in comparison with the more traditional liquid-solid separation methods and even with HPLC. In this sense it was possible to isolate flavonoid glycosides from ethyl acetate extract of Clusia criuva, in a very short operation time.
    Additional Material: 3 Ill.
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  • 121
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    Fast Solvating Gas Chromatography of Environmentally Important Compounds Using Polymer-Encapsulated Silica Particles (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 541-546 
    Details
    ISSN: 0935-6304
    Keywords: Solvating gas chromatography ; gas chromatography ; fast separation ; pesticides ; herbicides ; aldehydes ; packed capillary columns ; polymer-encapsulated silica ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Rapid separations of selected environmentally important polar compounds using polymer-encapsulated silica stationary phases and a carbon dioxide mobile phase under solvating gas chromatography (SGC) conditions are reported. Ten underivatized short chain aldehydes and ten nitrogen-containing herbicides were separated within 1 min and 5 min, respectively, using a 30 cm×250 μm i. d. column packed with diol-bonded, polyethylenimine (PEI)-coated, and hexamethyldisilazane (HMDS)-end-capped silica particles (5 μm, 120 Å). Seven organophosphorus pesticides were resolved in less than 5 min using a 30 cm×250 μm i. d. column packed with polymethylhydrosiloxane-deactivated and SE-54 encapsulated silica particles. Separation numbers per unit time increased with pressure and temperature ramps. Both rapid pressure and temperature programming can be used to increase the speed of SGC. The effects of pressure and temperature on apparent retention factors of solutes with various polarities were investigated using diol-PEI-HMDS silica particles in SGC.
    Additional Material: 9 Ill.
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  • 122
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    Evaluation of Dead Time Calculation in Reversed-Phase Liquid Chromatography Using a Multiparametric Mathematical Method (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 559-564 
    Details
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; dead time ; multiparametric least-squares adjustment ; homologous series ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In reversed phase liquid chromatography (RP-HPLC), the validity of a multiparametric non-linear least-squares regression iterative method for the determination of the column dead time tM and the regression parameter (slope b), based on the use of alkan-2-ones, alkyl aryl ketones, and 1-nitroalkanes has been evaluated. The determination of tM and b has been extensively studied for two mobile phase systems acetonitrile-water and methanol-water on seven octadecyl-C18 and one octyl C8 analytical columns. The calculated tM and b values were compared with those obtained by Guardino's and Grobler's methods. The influence exerted thereon by the nature of the homologous series, the mobile phase composition, and the packing materials were investigated.
    Additional Material: 5 Tab.
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  • 123
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    Supercritical Fluid Extraction (SFE) Optimization by Full-Factorial Design for the Determination of Irganox 1076, Irgafos 168, and Chimassorb 81 in Virgin and Recycled Polyolefins (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 553-558 
    Details
    ISSN: 0935-6304
    Keywords: SFE ; experimental design ; additives ; recycling ; polyolefins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The performance and feasibility of supercritical fluid extraction (SFE) applied to the extraction of some antioxidants (Irganox 1076, Irgafos 168) and one UV-stabilizer (Chimassorb 81) from both virgin and recycled low density polyethylene (LDPE), and virgin high density polyethylene (HDPE) are studied. Due to the high number of variables a full-factorial design has been applied to minimize the number of experiments required to reach the optimum extraction conditions. Further analysis has been carried out off-line by reversed-phase HPLC. Modification of the physical properties of the polymeric matrix and increased number of recycling cycles as well as the influence of physical properties on the efficiency of SFE are also discussed.
    Additional Material: 1 Ill.
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  • 124
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    Capillary Electrophoresis as an Efficient Tool in the Determination of Low Association Constants between Polyhydroxy Compound and Samarium Cation (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 595-598 
    Details
    ISSN: 0935-6304
    Keywords: Xylitol ; samarium ; weak association ; equilibrium constant ; capillary electrophoresis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
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  • 125
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    Effects of Blending Bare-Silica and Reversed-Phase on Retention of Neutral Compounds in Capillary Electrochromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 599-603 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; retention ; mixed stationary phases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Most commercially available instruments for capillary electrochromatography (CEC) have a fixed configuration and lack the flexibility to use shorter columns. Applying a blended stationary phase (a phase consisting of a given ratio of bare silica and reversed phase material) can simulate columns of different length in CEC. The goal of this work was to examine the effect of the degree of blending of reversed-phase columns (with bare silica) on the speed of the separation of neutral compounds in CEC. Optimum column packing mixture was determined from the variation of the solute retention factors as a function of the ratios of blending of reversed-phase and bare silica. By adjusting the column composition, solute retention factors and the analysis run time were halved when compared to a pure reversed-phase column of the same length. Stationary phase blending can be considered as an additional parameter to mobile phase variation, column temperature and applied electric field for the optimization of selectivity and analysis time. By adjusting the stationary phase composition, mobile phase composition, column temperature and applied electric field, the analysis run time of neutral components was decreased more than 75% when compared to a separation obtained on neat reversed-phase column of the same dimensions. The linear dependence of the retention factors as a function of the blend ratio (reversed phase/bare silica) offers a framework for designing a “blended” packed capillary column for CEC separations.
    Additional Material: 5 Ill.
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  • 126
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    Comparison of Retention Indices of Some Explosives and Related Compounds Calculated by Different Mathematical Methods in Reversed-Phase Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 613-618 
    Details
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; retention index ; multiparametric least-squares adjustment ; homologous series ; nitramines ; nitroaromatics ; aminoaromatics and nitrophenols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In reversed phase liquid chromatography, the retention indices of some neutral and acidic explosives and related compounds (nitramines, nitroaromatics, aminoaromatics, and nitrophenols) based on the alkan-2-one, alkyl aryl ketone, and 1-nitroalkane retention index standards have been determined by the application of a new mathematical adaptation method, viz. a multiparametric least-squares regression iterative method. This method was applied to two types of columns. The first group includes six octadecyl-C18 columns with different packing materials and obtained from different manufacturers, while the second group comprises one octyl-C8 column. The retention indices have been extensively studied using either methanol-water or methanol-phosphate buffer mobile phase systems. The calculated multiparametric retention indices values were compared with those obtained by Guardino's, Grobler's, and Kovàts' methods. The influences of the concentration of the organic modifier in the mobile phase, aqueous mobile phase pH, and the column packing material on the retention indices of the explosives were also investigated. Good agreement was observed between the retention indices calculated by the use of the four mathematical methods for both neutral and acidic explosives.
    Additional Material: 4 Tab.
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  • 127
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    Extraction and Clean-Up Method for the Determination of Twenty Organochlorine Pesticide Residues in Tomatoes by GLC-ECD (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 619-622 
    Details
    ISSN: 0935-6304
    Keywords: Organochlorine compounds ; pesticides ; food analysis ; tomatoes ; GLC-ECD ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A method is described for the simultaneous extraction and determination of twenty organochlorine pesticides residues [hexachlorocyclohexane (HCH) isomers (α, β, γ, δ), aldrin, dieldrin, endrin, heptachlor and its epoxide (HE), hexachlorobenzene (HCB), α-endosulfan, o,p′-DDD, p,p′-DDD, o,p′-DDE, p,p′-DDE, o,p′-DDT, p,p′-DDT, dicofol, methoxychlor, and mirex] that were spiked in tomatoes. Samples were extracted with ethyl acetate, and the extract was subjected to a rapid clean-up using a Florisil column. The residues were determined by GLC-ECD using two columns of different polarity. The calibration graph correlation coefficient ranged from 0.9903 to 0.9990. The recoveries ranged from 95 to 99% with relative standard deviation ranging from 0.5 to 14.7% in the concentration range 0.005 to 0.2 μg/g. The limits of detection ranged from 0.004 to 0.05 μg/g and the limits of quantification ranged from 0.005 to 0.174 μg/g.
    Additional Material: 1 Ill.
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  • 128
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    Total p-Nitrophenol Determination in Urine Samples of Subjects Exposed to Parathion and Methyl-Parathion by SPME and GC/MS (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 628-630 
    Details
    ISSN: 0935-6304
    Keywords: p-Nitrophenol ; urine ; SPME ; GC/MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 129
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    A Rapid Method for Fingerprinting the Organic Fraction in Archeological Samples Using a PTV as a Thermodesorber (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 635-638 
    Details
    ISSN: 0935-6304
    Keywords: High resolution gas chromatography ; thermal desorption ; archeological cosmetic powders ; PTV injector ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 5 Ill.
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  • 130
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    Properties and Applications of Mixed Packing Capillary Electrochromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 666-670 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; mixed packing technique ; electroosmotic flow ; retention mechanism ; fast analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixed packing capillary electrochromatography (MP CEC) with the stationary phase comprising a physical mixture of strong cation exchange (SCX) phase and octadecysilyl (ODS) phase was developed. With the existence of a sulfonic acid group on the surface of SCX, not only could the electroosmotic flow (EOF) remain high at low pH, but also the hydrophilicity of the stationary phase was increased greatly, leading to broad adaptable ranges of both pH and organic modifier concentration in the mobile phase. At the same time, with the coexistence of C18 on the surface of ODS, both the retention and the resolution of samples were improved. Accordingly, MP CEC combined the advantages of both SCX and ODS columns. Effects of operation parameters on EOF and the capacity factors of solutes as well as the retention mechanism of such a column were studied systematically. In addition, MP CEC columns were used in the analysis of strong polar solutes as well as for the high speed separation of acidic, basic, and neutral compounds in a single run.
    Additional Material: 7 Ill.
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  • 131
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    Cyclocholates as Chiral Selectors for Capillary Gas Chromatography - Effect of Temperature Conditioning on the Chromatographic Behavior of the Stationary Phase (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 671-678 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective capillary gas chromatography ; chiral stationary phase ; chiral recognition mechanism ; cholic acid ; cyclocholates ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The suitability of cyclocholates as chiral selectors in gas chromatography has been evaluated. We present the synthesis and characterization of two cyclocholates, viz. 3α,7α-diacetoxycyclo[3]cholate and 3α,7α-diacetoxycylo[4]cholate. Mixtures of these new selectors with polysiloxanes were tested as chiral stationary phases in capillary gas chromatography. Several enantiomer separations of common racemates were achieved with the 3α,7α-diacetoxycyclo[3]cholate at 10% in OV-1701 (w/w). It was shown that column efficiency was strongly dependent on temperature and that enantioselectivity was very sensitive to column conditioning. This chromatographic behavior suggested that cyclocholates were only dispersed in polysiloxane. Thus, it was assumed that chiral discrimination occurred via enantioselective adsorption interactions of enantiomers at the surface of the solid chiral selector dispersed in the polysiloxane matrix OV-1701.
    Additional Material: 11 Ill.
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  • 132
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    Comparative Study of Packed and Capillary Column Chromatography for the Characterization of Vacuum Gas Oils (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 683-686 
    Details
    ISSN: 0935-6304
    Keywords: Vacuum gas oils ; packed column chromatography ; n-paraffins ; carbon number distribution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Gas chromatographic methods are of widespread use in the petroleum industry for assessing petroleum and derivatives quality. The feedstocks for catcracking processes are very sensitive to the n-paraffin contents, which can be accurately determined using capillary column chromatography. Nevertheless, packed column chromatography does have potential advantages, viz. sometimes shorter analysis times, lower costs, higher column capacity, for vacuum gas oil analysis. This paper presents a method for such a determination using a Dexsil-300 packed column. The results obtained (n-alkane contents, carbon number distribution) agree fairly well with those obtained on a 30 m × 0.25 mm DB-1 fused silica capillary column.
    Additional Material: 3 Ill.
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  • 133
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    Preface (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. v 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230102
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  • 134
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    Characterization of bond and current correlation structures in a molecular many-electron wave function (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 27-45 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method has been developed to analyzed the bond and current correlation structures of a molecular many-electron wave function. It is shown that the second order density matrix contains information about the bond and current correlations in its off-diagonal components with respect to the indices of orbital basis functions. We break down the off-diagonal correlation functions into five kinds: charge, spin scalar, spin quadrupole, charge spin, and spin polar correlation functions. For a real wave function, the four correlation functions, except for the spin polar one, have only symmetric-symmetric and antisymmetric-antisymmetric components. The former components give site-bond and bond-bond correlations of charges and spins, while the latter components give current-current correlations of charges and spins. The spin polar correlation function has only symmetric-antisymmetric components that give site-current and bond-current correlations of spins. The five off-diagonal correlation functions are expressed in terms of the off-diagonal components of the second order density matrix. The linked off-diagonal correlation functions are defined in that they give dynamical bond and current correlations. The method is applied to the analyses of the bond and current correlations in the low lying exact eigenstates of the PPP Hamiltonian of benzene.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230105
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  • 135
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    Clebsch-Gordan coefficients for chains of groups of interest in quantum chemistry. III. The point symmetry groups (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 115-125 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work amalgamates some basic elements defined in the first paper of this series and in related papers with the theory of coupling coefficients for an arbitrary group with the view of generating the Clebsch-Gordan coefficients and V symbols for point symmetry groups. The connection between Clebsch-Gordan coefficients and V symbols is established for an arbitrary group in a form that reduces to the one known for the chain SU(2) ⊃ U(1). The Clebsch-Gordan coefficients and V symbols of any point symmetry group G are shown to be obtainable from Clebsch-Gordan coefficients and \documentclass{article}\pagestyle{empty}\begin{document}$ {\bar f} $\end{document} symbols of the chain SU(2) ⊃ G through the resolving of a system of nonlinear equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230113
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  • 136
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    Thomas-Fermi term as the simplest correction to the Weizsacker term (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 127-133 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nature of the correlation function G(1,2) appearing in the definition of the reduced first order density operator γ′(1,2) = ρ(1)1/2ρ(2)1/2G(1,2) is analyzed. It is shown that when G(1,2) is expanded in terms of plane waves in the context of a single-determinant approximation to the wave function, the correction to the Weizsacker term in the kinetic energy density expression is the Thomas-Fermi term.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230114
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  • 137
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    Stability of chemical species (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 271-308 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the framework of our theoretical approach of the structure and reactivity of chemical intermediates we have been led to reexamine the concept of stability which is widely used by the experimentalists often without specifying its true meaning. In this work we propose a more general definition of the concept of stabilization energy, namely, \documentclass{article}\pagestyle{empty}\begin{document}$$ SE = \Delta H_a - \Sigma N_{AB} E_{AB} $$\end{document} where ΔHa is the heat of atomization of the species under consideration and the EAB's are standard bond energy terms derived from the heats of atomization of reference compounds. Using experimental heats of formation or semiempirical ones deduced from theoretical heats of reaction of appropriate isodesmic processes, we have calculated the stabilization energies of various types of chemical species: saturated, unsaturated and conjugated molecules, free radicals, carbocations, and carbanions. The results obtained can be rationalized in terms of steric hindrance, angular strain, polar interactions, electron delocalization, and substituent effects. Moreover, we have shown that heats of hydrogenation and bond dissociation energies do not provide accurate information on the thermodynamic stabilization of unsaturated compounds and free radicals, respectively. Among other applications the concept of stabilization energy allowed us to propose a detailed classification of free radicals and to rationalize their reactivity. Considering the particular case of radical recombination reactions we have been able to deduce interesting equations showing the relations between the concept of stabilization energy and other quantities commonly used in chemical physics, namely, the bond cleavage enthalpy [BDE(C—C) if one considers alkane thermolysis], the thermodynamic stability measured by the free enthalpy change of a given reaction, and the kinetic stabilization related to the activation energy of a chosen chemical process \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm BDE}(R - R) = E(R - R) - 2{\rm SE(R}^ \cdot {\rm)} + {\rm SE(R} - R{\rm),}} \\ {\Delta G^0_r 2{\rm SE(}R^ \cdot {\rm)} - {\rm SE(R} - R{\rm)} - E(R - R) - T\Delta S^0,} \\ {E_a (r) = \alpha [ - {\rm BDE(}R - R{\rm)}] + \beta ({\hbox{Evans - Polanyi relation}}),}\\ {E_a (r) = a[2{\rm SE(R}^ \cdot )} - {\rm SE(}R - R{\rm)] + }b{\rm .} \end{array} $$\end{document} This analysis allowed us to give a new interpretation of the adjectives transient, persistent, and stable introduced by Griller and Ingold and to show that the persistence of a radical may be due to other factors than steric ones. In conclusion, the concept of stabilization energy appears to be a good tool for rationalizing the static and dynamic properties of chemical species.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560230125
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  • 138
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    Two-Dimensional fully numerical solutions of molecular Schrödinger equations. II. Solution of the Poisson equation and results for singlet states of H2 and HeH+ (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 319-323 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two-dimensional fully numerical solutions of the Hartree-Fock problem are reported for the singlet ground states of H-, He, H2, and HeH+. The H2 energy at R = 1.4 a.u. is -1.13362957 a.u.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230127
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  • 139
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    Editorial Comments (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. vii 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230202
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  • 140
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    Approach to N representability (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 399-404 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper, some operator endomorphisms which give rise to conditions for N representability of pth order density matrices are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230208
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  • 141
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    Cr—Cr Multiple bonding in binuclear complexes (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 425-436 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple analysis of the bonding between the d orbitals in binuclear complexes of chromium indicate that the usual multiple bond picture used to describe these systems is incomplete. This analysis is fairly general and depends only on the symmetry of these complexes and the rather weak coupling between the 3d orbitals on the two metal centers. A series of INDO calculations on Cr2Cl8-4 and Cr2(CH3)8-4 are reported, and suggest that the dominant description of the bonding is one of two Cr atoms antiferromagnetically coupled. Although this description properly accounts for the eclipsed versus staggered conformations found for these systems, the calculated bond length is too long. An analysis of the components of the wave function suggests that the role of multiple bonded structures (configurations) may be small but is important in its influence in shifting the very flat potential energy surfaces to shorter Cr—Cr distances.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230211
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  • 142
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    Theoretical study of the effect of substituents on electrophilic addition to olefins: Ab initioMO approach with energy decomposition (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 491-495 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction energies of proton with ethylene and substituted ethylenes in a positive bridged ion have been calculated by ab initio MO method with STO-3G basis set, and the energies were further decomposed according to decomposition scheme proposed by Kitaura and Morokuma [Int. J. Quantum Chem. 10, 325 (1976)].
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230219
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  • 143
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    Finite-field calculations of molecular polarizabilities using field-induced polarization functions. II. Second- and third-order perturbation correlation corrections to the coupled Hartree-Fock polarizability of HF (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 447-457 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Correlation corrections to coupled Hartree-Fock (CHF) static dipole polarizabilities and dipole moment of the HF molecule are calculated using third-order Rayleigh-Schrödinger perturbation theory with Møller-Plesset partitioning (RSMP) in a finite-field procedure. Computations are also made for the dipole moment and polarizability derivatives at the equilibrium internuclear separation. Three different basis sets using contracted Gaussian orbitals augmented by field-induced diffuse polarization functions have been employed to investigate the nature of variation of the properties under study, and the importance of field-induced diffuse polarization functions is discussed. [2/1] Padé approximants are used to accelerate the convergence of the properties. The correlated dipole moment and polarizability values are in excellent agreement with the existing theoretical and experimental values. The dipole moment derivative is in perfect agreement with the existing correlated value. However, the polarizability derivatives at SCF and correlated levels differ appreciably from the existing SCF values and represent as improvement.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230213
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  • 144
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    Molecular geometry of benzosemiquinone radicals: Radicals from resorcinol and its derivatives (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 477-481 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The observed proton hyperfine coupling constants of radicals from resorcinol and 2-carboxylic, 5-carboxylic, and 5-methyl resorcinols in acidic and alkaline solution were reproduced by means of the INDO (intermediate neglect of differential overlap) with molecular geometry adjusting method. The bond lengths of C—O were longer in acidic solution than in alkaline solution and the total energies were lower in acidic solution than in alkaline solution. The assignments of the coupling constants of the radicals from resorcinols were |A2| 〉 |A5| in alkaline oxidation and |A2| 〈 |A5| in acidic oxidation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230217
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  • 145
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    Potential energy surface determinations for nonrigid molecules: Application to acetone (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 507-516 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present work, the problem of the determination of the potential energy surface for nonrigid molecules is examined in the case of the double rotation of the methyl groups in acetone. From the symmetry adapted functional form for the potential, the minimum number of configurations to be calculated is deduced in order to have a reliable surface. With this consideration in mind, the potential energy surface of acetone is determined in some Hartree-Fock semiempirical (CNDO/2) and ab initio procedures with different standard basis sets. In addition, ab initio calculations are performed using different sets of floating Gaussian functions in order to introduce some polarization effects in the wave function. Finally, the influence of the electronic correlation effects in the barrier height, and the role of the possible relaxation of the structure during the rotation is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230221
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  • 146
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    Semiclassical time-correlation function approach to collisional energy transfer into many-atom systems (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 551-560 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cross sections for energy transfer into many-body systems can be expressed in terms of time-correlation functions (TCFS) of transition operators. A semiclassical version is presented by treating internal motions as quantized and relative motions as classical. The time evolution of internal motions can be calculated in the Heisenberg picture and avoids expansions in target states. The decoupling of fast and slow internal motions is treated and applied to vibrational-rotational decoupling in polyatomic molecules. Results are presented for Li+-CO2 collisions.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230225
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  • 147
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    Water chain intervention in hydrolytic and tautomeric reactions (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 587-593 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Water chain intervention in the hydrolysis of methyl fluoride and in some tautomeric 1,3 proton transfer reactions has been studied. The results show that in solution the process are neither unimolecular nor bimolecular as in the gas phase, but are multimolecular, where the geometric parameters of the solvent intervene in the reaction coordinate.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230229
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  • 148
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    Large-scale RPA calculations of chiroptical properties of organic molecules: Program RPAC (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 595-611 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The computational considerations involved in calculating ordinary and rotatory intensities and electronic excitation energies in the random phase approximation (RPA) are examined. We employ a localized orbital formulation in order to analyze the results in terms of local and charge-transfer excitations. Occupied orbitals are localized by the Foster-Boys procedure. The virtual space is transformed into a localized “valence” set that maximizes dipole strengths with the occupied counterparts, and a delocalized remainder. The two-electron integral transformation is performed with an efficient algorithm, based on Diercksen's, that generates only the particle-hole-type integrals required in the RPA. The lowest solutions of the RPA equations are obtained iteratively using a modification of the Davidson-Liu simultaneous vector expansion method. This allows the inclusion of the entire set of particle-hole states supported by a basis set of up to 102 orbitals. Calculations at this level give better excitation energies and intensities than SDCI methods, at substantial savings in computational effort. Comparative timings, computed results and analysis in terms of localized orbitals are given for planar and distorted ethylene using extended atomic orbital bases including diffuse functions. The results for planar ethylene are in excellent agreement with experiment.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230230
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  • 149
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    Time-dependent Schrödinger equations: Symmetry breaking, separation of variables, and nonlinear effects (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 663-678 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nonlinear equations are important for the description of dissipative processes and soliton-related phenomena. One of the principal aims of the theory of symmetry breaking in quantum mechanics is to provide a systematic method for introducing interactions which reduce the symmetry of a system. Such a method is applied here to compute the general form of the symmetry-breaking interaction F(x,t, Ψ, Ψ*) for the time-dependent Schrödinger equation in one spatial dimension \documentclass{article}\pagestyle{empty}\begin{document}$$ \left[{\partial _{xx} + 2i\partial_t - 2g_2(t)x^2 - 2g_1(t)x - 2g_0 (t)} \right]\psi (x,t) = F(x,t,\psi,\psi *). $$\end{document} For F = 0, it has been shown that the Lie algebra of space-time invariances of this equation is S1 = s1 (2,IR)□w1, the Schrödinger algebra. Following the method of Boyer, Sharp, and Winternitz, all conjugacy classes of subalgebras of S1 are given. For each subalgebra, the most general form of the interaction term F(x,t, Ψ, ψ*) is constructed. The potential F then reduces the symmetry from S1 to the considered subalgebra. Furthermore, the one-dimensional subalgebras of S1 obtained above partition S1 into orbits of operators. To each orbit there corresponds a coordinate system in which the above equation separates variables. A partial resolution of the solutions of the above equation has been obtained by exploiting this relation. The algebraic approach to symmetry breaking yields a rich variety of interaction terms F, which appear to generalize the nonlinear Schrödinger-Langevin-Kostin equation for nonconservative systems and the so-called nonlinear Schrödinger equation. A criterion in terms of the existence or nonexistence of Bäcklund transformations is conjectured in order to distinguish between dissipative and soliton equations.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230236
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  • 150
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    Unusually large electrostatic field effect of the buried aspartate in serine proteinases: Source of catalytic power (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 723-728 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Calculating the electrostatic potential around the Ser-His-Asp catalytic triad in serine proteinases the very important substituent effect of the buried aspartate is revealed. It is found that the strong Coulomb field of this distant but charged side chain considerably enhances the nucleophilicity of the active serine hydroxyl group. The interpretation of the vital importance of aspartate may replace the “charge-relay” hypothesis which seems to be disproved in the light of recent experiments.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230241
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  • 151
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    Masthead (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230301
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  • 152
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    Effective handling of a large configuration state function expansion for an MCSCF state and improved efficiency for two-electron integral transformations in MCSCF (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 789-809 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Effective solutions for two difficulties which may be present in MCSCF calculation are discussed: (i) We show how the large configuration state function state expansion case may be handled simply and effectively without the introduction of extraneous projection operators or Lagrange multipliers; (ii) we present a simplified two-electron integral transformation procedure which significantly reduces the operation count (and hence computational efficiency is increased) for second order and particularly for third order MCSCF procedures. The procedures we introduce use some freedom available in the orthogonal complement Cl space and the virtual orbital space to simplify MCSCF calculations.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230304
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  • 153
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    Improved SCF interaction energy decomposition scheme corrected for basis set superposition effect (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 847-854 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modified scheme for SCF interaction energy decomposition has been proposed where the nonphysical basis set superposition error (BSSE) has been corrected by means of the counterpoise method. A new procedure to separate the exchange and induction energy terms free of nonphysical BSSE has been tested in the case of the H2O dimer. The first order BSSE appears to be non-negligible for strong hydrogen bonded complexes. In addition the scheme allows separation of the long-controversial charge-transfer contribution within the induction term, which has been considerably overestimated in previous studies.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230308
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  • 154
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    Single versus double insertion in a simple intermolecular carbene reaction (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 887-890 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The carbene reaction 1CH2 + C2H6 was studied with the semiempirical method SINDO 1. The pertinent transition states and products were obtained by geometry optimization on a CI surface. We find the insertion reaction forming C3H8 greatly favored compared to the double insertion leading to CH4 + C2H4. The result is qualitatively the same for the reaction of the two possible intermediate radicals CH3 and C2H5. The geometries and energies of all transition states are presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230312
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  • 155
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    Computer-generated formulas for some three-center molecular integrals over Slater-type orbitals (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 953-957 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Exact computer-generated formulas can be produced for each term of an infinite series that gives the value of three-center Coulomb integrals over Slater-type orbitals of the s-type with equal screening constants. As a specific example, the Coulomb energy of an equilateral triangular arrangement of all 1s orbitals is calculated using seven terms of an infinite expansion to obtain an answer comparable to earlier work in elliptic coordinates. Generalization to all three-center cases of this implementation of the Löwdin α-function method is straightforward.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230318
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  • 156
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    Ordinary field-theoretic methods for self-consistent wave functions which describe bond formation and dissociation. II. Commutative coupling casePresented at the Symposium on Local Density Approximations in Quantum Chemistry and Solid State Theory, H. C. Øorsted Institute, Copenhagen, June 1982. (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 905-914 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hartree-Bogoliubov-Valatin (HBV) theory may be implemented with Lipkin Hamiltonians to obtain self-consistent BCS wave functions which describe bond formation and dissociation. These wave functions are in turn vacuua for Nambu's representation of Feynman-Dyson-Goldstone diagrammatic perturbation theory, and hence provide suitable references for the many-body treatment of correlation. Exact SCF solutions of the HBV equations are equivalent to special even-replacement MC-SCF solutions. The latter are similar to generalized valence bond theory, and require one Fock operator for each one-particle shell. The commutative coupling case of HBV theory is realized when the number-conserving renormalized one-body and number-nonconserving pairing operators commute. In this case, a set of orbital equations which involves a single Fock operator may be solved. Since this could prove to be a significant simplification for large systems, the commutative coupling and exact solutions are compared here for the fragmentation of H2 and F2. Results suggest that commutative coupling orbitals will be useful for the aforementioned many-body theory.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230314
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  • 157
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    Quantum study of the ground state of a series of unsaturated boron-nitrogen compounds by the MNDO method. I. Geometries and stabilities (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 891-904 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A MNDO study of molecular geometries, enthalpies, formation, atomization, bond separation, and hydrogenation of a series of unsaturated boron-nitrogen compounds, linear with two and three members and cyclic with three, four, five, and six members are presented. For all these molecules, MNDO calculations are in excellent agreement with available ab initio calculations or experimental data. The high rotational barrier in aminoborane H2BNH2, 30.6 kcal/mol, and the length of bond in iminoborane HBNH, 1.183 Å, imply strong double and triple BN bond character in these two molecules. In the odd membered heterocycles, examination of the molecular geometries and energies of equilibrium states shows that in all cases, the stability of the compounds grows with the number of boron atoms and decreases with that of the nitrogen atoms. Moreover, compared study of the two BN-fulvenes with their homologous hydrocarbon shows that only BN (BB)-fulvene has a polyenic structure similar to that of fulvene.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230313
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  • 158
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    Multiconfigurational Hartree-Fock response functions (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 959-971 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The linear, quadratic, and cubic response of a multiconfigurational Hartree-Fock state to a time independent one-electron perturbation has been derived. A comparison between the exact response functions as obtained from Rayleigh-Schrödinger perturbation theory and the multiconfigurational Hartree-Fock response functions allows a identification of matrix elements of the perturbation operator between the ground and excited states and between excited states. We discuss some ambiguities which result from such an identification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230319
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  • 159
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    Monte Carlo simulations of solid nitrogen in the isothermal-isobaric ensemble with an ab initioSCF-CI potential (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 991-998 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monte Carlo simulations in the isothermal-isobaric ensemble for the α phase of solid N2 have been carried out with two different pair potentials obtained from ab initio quantum chemical calculations. Comparison is made with data obtained from empirical potentials as well as with experimental data, and in general, the agreement with experiment is found to be good. It is also found that the differences between experiment and theory can largely be attributed to correlation effects, not considered in the quantum mechanical calculations of the pair potential.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230322
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  • 160
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    Application of AGP wave functions to the ground states of Li2 and CH+ (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1047-1056 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The AGP wave function is used to describe the ground state potential energy curves of Li2 and CH+. Moderate size basis sets are used. The computational aspects of the AGP optimization are discussed and the nature of the AGP wave function versus internuclear separation is examined.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230328
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  • 161
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    Clustered hydrogenic centers in impure semiconductors (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1155-1163 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Doped semiconductors with shallow impurities provide an ideal situation to study a collection of hydrogenlike atoms under controllable experimental conditions. We present the results of recent cluster calculation on the electronic properties of such systems.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230406
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  • 162
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    Comparison of theoretical and thermodynamic values of interconstituent interactions in DNA (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1283-1293 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Experimental base stacking and hydrogen bonding enthalpies, as determined from double stranded DNA melting studies, are compared with theoretical calculations of interactions between the respective DNA interconstituent components. Comparisons are made in relation to the differences in magnitudes, sequence dependent spreads, and trends. It is shown that the use of an effective dielectric constant reconciles the differences between the experimental and theoretical values. Suggestions are made for calibration of potential functions suitable for nucleic acid conformational analysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230417
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  • 163
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    Recent investigations on the electronic structure of the fourth and fifth group transition metal monocarbides, mononitrides, and monoxides (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1317-1353 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An overview is given here of band structure calculations on the fourth and fifth group transition metal monocarbides, mononitrides, and monoxides, published since the review article by Calais [J.-L. Calais, Adv. Phys. 26, 847 (1977)]. Furthermore, the relations of three categories of experimental properties, which allow insight into the electronic structure of the above mentioned compounds, and the results of band structure calculations are discussed. Theoretical predictions are compared with experimental findings. The considered experimental properties are valence band photoemission spectra, valence band x-ray emission spectra, and optical properties.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230420
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  • 164
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    Conformational studies of the β(1→3) linked disaccharide component of the immunologically active pentasaccharide of the Forssman antigen (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1433-1439 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energy calculations at the PCILO level of approximation were performed on β(1 → 3) linked disaccharide consisting of N-acetylgalactosamine and galactose of the Forssman antigen to examine the side group conformations and their influence on the mutual orientations of the two pyranosyl rings. Two low energy regions for the glycosidic bond conformation have been located in the grid search using classical potential functions. The PCILO energy minimizations were then carried out in each of these regions. The preferred orientations of the nonreducing pyranosyl ring relative to the reducing ring were found to be in agreement with the available x-ray results. Moreover, the orientations of groups attached to the anomeric carbons were in good accordance with the requirements of the exo-anomeric effect.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230425
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  • 165
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    Molecular electrotatic potential of a triple stranded helix: Poly(dT)·poly(dA)·poly(dT) (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1451-1461 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular electrostatic potential of the triple helix poly(dT)·tpoly(dA)·poly(dT) is calculated, and the results are examined in relation to those obtained for its component double and single helical parts. For the double helix presenting the standard Watson-Crick hydrogen bonds, the deepest potentials are formed on the side of the major groove, a situation similar to that observed in the A-DNA duplex. For the double helix presenting Hoogsteen-type hydrogen bonds the deepest potentials lie in the major groove, on the side of the pyrimidine strand. In the triple helix the deepest potentials are located in the major groove in a narrow zone over the thymine bases of the Watson-Crick pair.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230427
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    Interacting stereo-irregular chains: A model for conducting polymers (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1363-1383 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Interacting stereo-irregular chains of hydrogen atoms, which simulate the topological structure of many conducting polymers, are generated by a computer and solved numerically with the unrestricted Hartree-Fock method with a modified spin polarized potential. The electron localization is investigated, and a mechanism for the interchain tunneling is discovered. Local antiferromagnetic ordering is derived which may explain the AF behavior observed in some conducting polymers.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230422
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  • 167
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    Quantum chemical studies on the conformational structure of bacterial peptidoglycan. V. PCILO Calculations on β(1 → 4) linked disaccharide of N-acetyl-glucosamine and N-acetyl muramic acid (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1441-1450 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The glycan moiety of the bacterial peptidoglycan consists of alternatingly β(1 → 4) linked disaccharides of N-acetylglucosamine (NAG) and its 3-O-D lactic derivative, N-acetyl β-D-muramic acid (NAM). PCILO conformational energy calculations have been carried out for NAG-NAM and NAM-NAG disaccharides to see whether or not the glycan strands possess a chitinlike structure as suggested by earlier workers. In agrement with recent experimental findings, the present results also suggest that the chitinlike structure is energetically disallowed. Furthermore, the bulky N-acetyl substituents at C2 positions of the two sugar molecules are found to be relatively less important in stabilizing mutual orientations of the two pyranosyl rings.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230426
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  • 168
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    Symmetry determined orbital and group overlap (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1479-1492 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The MO theory of structural polyhedrons is one of the basic subjects closely related to the bonding theory of complex compounds and clusters. A series of valuable papers on this subject have been contributed by Hoffman, Wade, King, and Lauher et al. A method called “group overlap method” for constructing the symmetry orbitals and for calculating the group overlap integrals is proposed. It is hoped that the group overlap method may be used for the qualitative and quantitative MO study of structural polyhedrons.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230430
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  • 169
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    Ab initioMODPOT/VRDDO/MERGE calculations on energetic compounds. III. Nitroexplosives: Polyaminopolynitrobenzenes (including DATB, TATB, and tetryl)Paper XVIII in the series “Molecular Calculations with the Nonempirical Ab Initio MODPOT/VRDDO/MERGE Procedures.” (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1493-1504 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quantum chemical ab initio MODPOT/VRDDO calculations have been carried out on the following aminonitrobenzenes for which crystal structures had been determined experimentally: 4-nitroaniline; N,N-dimethyl-p-nitroaniline; 2,4,6-trinitroaniline; 1,3-diamino-2,4,6-trinitrobenzene (DATB - Form I); 1,3,5-triamino-2,4,6-trinitrobenzene (TATB); 2,3,4,6-tetranitroaniline; N-methyl-N,2,4,6-tetranitroaniline (Tetryl); and N-(β,β,β-trifluoroethyl)-N,2,4,6-tetranitroaniline. These quantum chemical calculations were performed on the molecules in their conformations as found in their crystal structures. The calculations were carried out with our own ab initio programs which also incorporate as options several desirable features for calculations on large molecules: ab initio effective core model potentials (MODPOT) which enable calculations of valence electrons only explicitly, yet accurately, and a charge conserving integral prescreening evaluation (which we named VRDDO-variable retention of diatomic differential overlap) especially effective for spatially extended molecules. Aminonitrobenzenes are especially interesting since there are inherent intramolecular ring distortions and deviations from planarity and intramolecular hydrogen bonds as well as intermolecular hydrogen bonds causing further deviations from planarity. The theoretical indices resulting from the quantum chemical calculations are relevant to a number of properties and behavioral characteristics of these molecules, both intramolecular and intermolecular. The charges on the atoms [from the gross atomic populations (GAP's)] are needed for calculation of the atomic multipole-atomic multipole electrostatic contributions (a dominant factor) to the intermolecular interaction energies. These electrostatic interaction energies are part of the input necessary for calculations on the crystal packing and densities of these molecules. These GAP's are also of value in interpreting the experimental photoelectron and ESCA spectra of these molecules. The total overlap populations (TOP's) between atoms are related to the inherent bond strengths and can serve as a quantitative replacement for the old empirical bond length-bond order-bond energy relationship still used by explosives chemists to identify the “target bonds” (the weakest bonds). The TOP's are of considerable value in predicting and tracing initiation and subsequent steps of explosive phenomena. The molecular orbital energies of the lowest unoccupied orbitals are of interest since nitroexplosives have been implicated in testicular toxicity and the initial metabolic activation appears to proceed through a one-electron reduction of the nitroexplosive.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560230431
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  • 170
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    Use of VN-1 potentials in Green's function calculations (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1571-1577 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analysis of the leading effects of a propagator approach to the calculation of resonance energies is presented. By comparison with ΔSCF results, a simple approximation formula has been developed which contains the main features of the VN-1 potential option and the diagonal Tamm-Dancoff approximation. This result is expected to be a useful guide for further refinements of the many-body aspects of the theory.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230438
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  • 171
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    Quantum chemical structure-activity relationships on β-carbolines as natural monoamine oxidase inhibitors (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1643-1652 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron density and the molecular electrostatic potential of the β-carbolines are studied using ab initio STO-3G wave functions. The analysis was done from the point of view of a previous model built with monoamine oxidase substrates and irreversible inhibitors. The results confirm the usefulness of the model and make it possible to propose new precision to the molecular electrostatic potential patterns needed to have monoamine oxidase inhibitory activity.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230445
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  • 172
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    Relativistic extended Hückel studies of cluster models of solid HgTe, CdTe, and PbTe: Densities of states and nuclear spin-spin couplingA full account of the present work is published in Ref. 5. (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1685-1685 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230451
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  • 173
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    Calculation of excited-state properties of some small molecules: Comparative study of the CNDO/S and CNDO/2-vn-1 potential methods (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1695-1705 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transition energy and geometry of the lowest excited (nπ*) singlet and triplet states of CO, CS, HNO, H2CO, HFCO, and F2CO molecules are calculated by CNDO/S and CNDO/2-VN-1 potential methods, and the results are compared with those of experimental and ab initio theoretical studies, wherever available. In the calculation of the vertical transition energy, the performance of the CNDO/S method is seen to be generally more satisfactory than that of the CNDO/2-VN-1 potential method, while the reverse is true for the excited-state geometry. The CNDO/S method as such fails to describe the geometry of the excited state, but a combined version (CNDO/S-2) of CNDO/S and CNDO/2, as well as the CNDO/2-VN-1 potential method is fairly successful in this regard.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560230502
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  • 174
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    Theoretical study of degree of covalency in some CoF6(n-) complexes (n = 4, 3, and 2) (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1753-1765 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the basis of a high-quality LCAO MO SCF calculation, covalency versus ionicity of a Co-F bond in the CoF6(n-) complexes, where n = 4, 3, and 2, is discussed. The overlap and gross atomic populations, delocalization of certain MOS, and the charge densities in the bond region as well as around F's all indicate that the covalency increases as n decreases or the valency of Co increases in these complexes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230506
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  • 175
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    Usage de l'Algègbre de Lie su (n) Dans l'Etude des Systèmes Quantiques à n Etats. I. Quelques Conséquences Générales (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1807-1816 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In an n level quantum system there is a relation between each density operator and an element of su (n) Lie algebra. This relation is also established between Cartan's subalgebras and the complete sets of compatible observables. A scalar product is then defined in this algebra in order to introduce orthonormal bases and to simplify many calculations about expectation values of observables. Therefore simple general rules were established which show how to determine (completely or partly), from linearly independent observables, the density operator of the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230510
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  • 176
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    Masthead (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230601
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  • 177
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    Elastic forward scattering of high-energy electrons and molecular electron density (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1891-1901 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The elastic forward scattering of high-energy electrons from molecules has been studied in the second Born approximation. An integral transformation has been adopted to evaluate the second Born integrals analytically without explicit use of molecular wave functions. In the high-energy limit, the differential cross section for the forward scattering is expressed in terms of electric dipole and quadrupole moments, the second moment of charge distribution with respect to the molecular center, and transition dipole moments. All these quantities are shown to be computable from molecular electron densities in the ground state.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230603
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  • 178
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    Hartree-Fock exchange energy of an inhomogeneous electron gas (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1915-1922 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We examine the short-range behavior of the spherically averaged Hartree-Fock exchange charge density by performing a simple Taylor expansion. On the basis of this expansion, a theoretical model is constructed that generates gradient correction terms to the local density approximation for the exchange energy of an inhomogeneous electron gas. In particular, we derive the Xαβ exchange energy functional and a theoretical value for the parameter β. Our value for β agrees well with previous empirical estimates, and with empirical calculations in the present work.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230605
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  • 179
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    On a unified treatment of diffusion and kinetic processes (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1931-1944 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By the means of gauge invariance of the continuity equation Fick's law of diffusion can be extended to also comprehend the chemical reaction. In the case of first-order reactions a complete set of eigenfunctions is obtained. These solutions provide a tool for pattern recognition in biochemical and biological problems (e.g., formation of chromosome banding). The transport equation, including reactions of second order, exhibits soliton solutions describing the propagation of a kinetic process in a medium (molecular chain, fluids, etc.). A relationship to the soliton solutions of the nonlinear Schrödinger equation and Korteweg-de Vries equation of hydrodynamics is also indicated. The propagation of a reactive process (transition state) occurs in many problems of molecular biology. The Brownian motion of ions undergoing a reaction of first order in a constant magnetic field is also exactly solved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230607
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  • 180
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    Gradient expansion correction to the Dirac exchange term in statistical models for the Na atom with shell structure (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1973-1978 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the study of the ground-state binding energy of atoms, relatively more attention has been paid to the gradient expansion of the kinetic energy term of the Thomas-Fermi-Dirac model than to the gradient expansion of the exchange term of this model. Recently Shih and Shih, Murphy, and Wang have focused on this problem and calculated the first gradient expansion correction to the Dirac exchange term by making use of electron densities constructed from Hartree-Fock wave functions. In previous work, aimed to introduce the shell structure of atoms via a variational procedure using the energy density functional formalism, electron densities have been obtained for the Na atom within the Thomas-Fermi-Dirac model with and without the Weizsäcker and Hodges gradient expansion corrections to the kinetic energy term. In this paper we make use of the respective electron densities and calculate the first gradient expansion corrections to the Dirac exchange term. The results show that, for the Na atom, the magnitude of this correction is about 1% of the magnitude of the total binding energy.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230611
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  • 181
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    Second- and higher-order convergence in linear and nonlinear multiconfigurational Hartree-Fock theory (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 25-60 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We discuss how the local convergence of Newton-Raphson and fixed Hessian MCSCF iterative models may be rationalized in terms of a total order of convergence in an error vector and a corresponding error term. We demonstrate that a sequence of N Newton-Raphson iterations has a total order of convergence of 2N and that a sequence of N fixed Hessian iterations has a total order of convergence of N + 1. We derive the error terms of a Newton-Raphson and a fixed Hessian sequence of iterations. We discuss the implementation of the fixed Hessian and the Newton-Raphson approaches both when linear and nonlinear transformations of the variables are carried out. Sample calculations show that insight into the structure of the local convergence of Newton-Raphson and fixed Hessian models can be based on an order of convergence and an error term analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240104
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  • 182
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    Quantum model of coherent X-ray diffraction: Extension to Bloch orbitals (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 113-126 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The description of electron density in solids by quantum theory and by x-ray diffraction experiments should closely coincide. A formalism for describing the electronic structure of single crystals in terms of a density matrix is presented. Iterative equations for calculating the density matrix in a basis of Bloch orbitals using measured crystallographic intensity data are derived. Numerical results are presented. The Bloch orbital formalism explicitly accounts for the mutual interaction of atoms in different unit cells, and is useful for insulators, semiconductors, and metals.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240110
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  • 183
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    Quantum chemistry literature data base bibliography of ab initio calculations for 1978-80. By K. Ohno and K. Morokuma, Elsevier, New York, 1982. Vol. 12 in Physical Sciences Data. Price: $104.75 (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 135-135 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240113
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  • 184
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    Method of recurrent construction of Löwdin spin-adapted wave functions. III. Löwdin basis and its permutation symmetry: Evaluation of overlap integrals (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 279-306 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Löwdin basis functions are introduced and their permutation symmetry is studied in detail. A simple relation between the Löwdin basis and the orthogonal basis constructed by means of Young-Yamanouchi units is established. Both analytical and recurrence formulas for the overlap integrals of the Löwdin and some relevant auxiliary functions are derived. The symmetry of the overlap matrix of the Löwdin basis functions is briefly discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240303
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  • 185
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    Vibronic coupling of electronic states. III. The definitive breakdown of the CBO potential picture within the framework of our modelFor Part II, see K. Gustav and R. Colditz, Int. J. Quantum Chem. 22, 31 (1982). (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 327-332 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The definitive breakdown of the CBO potential picture in consequence of the vibronic coupling of two electronic states is discussed on the basis of our model. The present treatment differs from that given in the literature.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240306
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  • 186
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    On the electrostatic properties of papain in relation to its enzymatic activity (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 353-371 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrostatic potentials and fields created by the thiol protease, papain, are computed on the surface envelope of the protein and in the region of its active site using a technique based on accurate multipole expansions of the electron density of appropriately chosen subunits. The effect of binding counterions to the protein is considered specifically. The possible role of the “electrostatic environment” in the functioning of the enzyme is discussed and it is found that this environment can favor the proton transfer between Cys 25 and His 159 that is thought to initiate its mode of action, but that the reasons for this appear more complicated than earlier models would suggest.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240404
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  • 187
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    Bond length alternation in cyclic polyenes. III. Alternant molecular orbital method (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 411-423 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bond length alternation problem in cyclic polyene models as described by the Pariser-Parr-Pople Hamiltonian and an empirical quasiharmonic π-core potential is investigated using the one-parameter alternant molecular orbital (AMO) method. It is shown that in contrast to the unrestricted Hartree-Fock (UHF) results, which lead to symmetric equidistant structures, the one-parameter AMO results yield bond length alternating structures similar to those obtained with the restricted HF approach. The correlation energy recovered by the AMO method is examined for the symmetric polyenes in the whole range of coupling constants for both the Pariser-Parr-Pople and Hubbard Hamiltonians and compared with exact full configuration interaction (FCI) results. For the first member of the cyclic polyene series we also compared the FCI and AMO correlation energies for different nuclear framework distortions. This comparison indicates that in contrast to the UHF results the fraction of the correlation energy recovered by the AMO approach is very uniform over the range of nuclear distortions considered. The AMO results thus strongly indicate the dimerization in the polyenic chains.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240407
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  • 188
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    Unusual random walks (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 435-452 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For most structures (molecules, graphs, lattices) a count of random walks for nonequivalent sites will give different numbers, particularly for walks of many steps. Occasionally one finds the same count of walks for nonequivalent sites. These have been termed “unusual walks” and have been closely examined in the case of trivalent graphs. While it remains to be understood what structural factors are critical, some regularities have been observed and are discussed. Unusual walks within a single structure signal “isospectural” points in a graph. A number of structures possessing unusual walks have been displayed, and a few constructive steps which do not alter the “unusual” characteristics of selected vertices have been indicated.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240503
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  • 189
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    Electronic Resource
    A molecular geometry invariant property of energy level set boundaries in z space (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 523-526 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Boundaries of electronic energy level sets in the nuclear charge space wZ can be parametrized as single valued functionals for any nuclear geometry of molecules, which property, combined with the general convexity of such level sets, leads to various electronic energy inequalities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240602
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  • 190
    Electronic Resource
    Electronic Resource
    SCF and CI Studies of Hund's rules for the effects of electronic correlation and delocalization. I (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 593-602 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In connection with the reinterpretation of Hund's multiplicity rules for molecules, a detailed study has been made of the energy differences in the total energy and its components for the triplet and singlet Πu states of the hydrogen molecule and the analogous states of the four- and six-membered hydrogen atom rings. For the hydrogen molecule, both SCF and CI studies indicated that the outer electron is considerably more contracted in the triplet than in the singlet state. In both approximations, the energy difference is dominated for all bond distances of chemical and physical significance by the electron-nuclear attraction component and not by the electron repulsion component as predicted by simple first-order perturbation theory. Although the correlation energy for each of the states is of the same magnitude as the energy differences considered here, the difference of the correlation energies is much smaller. It had little effect on the qualitative differences between these states of the hydrogen molecule. For the four- and six-membered rings, SCF studies were made on the lowest singlet and triplet states where one electron was promoted from the σg to a Πu orbital. Even though the coupled electrons were more delocalized in these cases, the electron repulsion became relatively more important. However in all cases, the lower state had the highest electron repulsion energy and lower electron-nuclear attraction. The triplet state continued to have the more contracted outer open-shell orbital.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240606
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  • 191
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    Electronic Resource
    Calculation in k space of integrals arising in the theory of Van der Waals forces. II. Formulas for arbitrary atoms (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 633-649 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Basic integrals arising in the momentum space formulation of the van der Waals forces are derived for arbitrary two atoms. These integrals are essentially the matrix elements of the Fourier transformed Coulomb operator and the Fourier transformed square of the Coulomb operator between any two Slater orbitals. The derivation is completely analytic and the results are expressed as finite series expansions in terms of auxiliary integrals. Recursion relations among the auxiliary integrals are developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240610
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  • 192
    Electronic Resource
    Electronic Resource
    On the Sanibel coefficients in the expansion of spin-projected slater determinants (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 729-745 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Every Slater determinant D may be uniquely analyzed in terms of spin components Dl = OlD which are pure spin eigenfunctions, so that S2Dl = l(l+1)D. Every component Dl = OlD may in turn be written as a sum of symmetric combinations of Slater determinants, Tk = [αμ-kβk‖αkβν-k], and the coefficients ck(l) in the expansion OlD = ∑k ck(l) Tk are known as the “Sanibel coefficients.” By using the relation S2Dl = l(l+1)D, a recursion formula for the coefficients ck(l) is derived, which is then explicitly solved in the special case when Sz has the pure quantum number m = 0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240615
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  • 193
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    A possible interpretation of atomic valency as a spontaneously broken symmetry responseWork supported in part by Université Pierre et Marie Curie, UER 52. (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 24 (1983), S. 697-706 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concept of atomic valency is looked at as a specific response of an atomic system to an arbitrary environment. It is shown, on the basis of a mathematical result in group actions theory, how valency might be related both to previously found Hartree-Fock deformed states and to the isotropy groups (up to a conjugation) of the extrema of the electronic energy functional.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560240613
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  • 194
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    Electronic Resource
    Editorial comments (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. vii 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230103
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  • 195
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    AGP Propagator calculationsThis work was sponsored by a grant from the National Science Foundation. (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 65-70 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of the antisymmetrized geminal power (AGP) consistent reference state for RPA polarization propagator calculations is explored. Illustrative applications to the three lowest electronic states (3B1, 1A1, and 1B1) of the methylene radical are reported with comparisons to other theoretical methods and experiment.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230107
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  • 196
    Electronic Resource
    Electronic Resource
    Comparative study of the Hartree-Fock and the Hartree-Fock-Slater method (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 235-248 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Hartree-Fock method (standard Roothaan closed-shell HF-LCAO theory) and the Hartree-Fock-Slater method (restricted HFS-LCAO-DV method developed by Baerends and Ros) have been compared with emphasis on the respective one-electron equations and on the matrix elements of the respective Fock operators. Using the same STO basis in the two cases, the matrix elements of the Fock operators and of their separate one-electron, Coulomb, and exchange contributions have been calculated for the same orbitals and density of the ground state of the diatomic molecule ZnO. The effects of methodical (exchange potential) and numerical (DV method, density fit) differences between the HF and HFS methods on the various matrix elements have been analyzed. As expected the methodical effect prevails and is responsible for the higher (less negative) values of the matrix elements of the HFS Fock operator compared to those of the HF Fock operator. Numerical effects are observable also and are caused by the difference in integration procedures (DV method), not by the density fit.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230122
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  • 197
    Electronic Resource
    Electronic Resource
    Classical limit of quantum mechanics in the large (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 99-113 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hilbert space may be regarded as a convenient standard approximation by interpolation and extrapolation to a unitary space, in general decomposable into a sum of semisimple spaces. In the limit we expect a particle theory expanded in powers of h according to the number of interacting particles. In the classical limit h tending to zero, phase space, with equations of motion reducible to Hamiltonian form, replaces Hilbert space. The modification of states by observing them is taken care of by considering probability distributions of petty ensembles. If the equations for any single observer can be made autonomous by replacing empirical time by universal time with an arrow we have a causal system. We then obtain the relation between probability and negentropy required for the second law of thermodynamics. An approximate Newtonian theory provides proximate particles with internal and external variables and admits the Poincaré group. For the internal variables we have approximately the Breit interaction. For the external variables we have equivalence for observers of the homogeneous Lorentz group of relativity. We introduce grand ensembles of ultimate particles, and nebulae as proximate particles in the large. We assume the Einstein principle of equivalence for the ten parameter set of observers suggested by relativity and suppose the second law of thermodynamics holds for each observer. The Einstein law of gravitation follows in classical theory to the order of the reciprocal of the large constant, in general with positive natural curvature as well as that corresponding to mass. Replacing particle interactions by fields we include them in classical theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230112
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  • 198
    Electronic Resource
    Electronic Resource
    Correlation effects in externally perturbed many-electron systems (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 147-167 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Different methods for the calculation of the electron correlation contribution to atomic and molecular properties are analyzed and evaluated. The methods based on the self-consistent solution of the external perturbation problem are shown to offer several formal and computational advantages. The analysis of the correlation perturbation series for properties of many-electron systems indicates the importance of the appropriate treatment of unlinked diagrammatic contributions. In particular, the standard limited configuration interaction scheme based on single and double substitutions in the reference function may significantly suffer from the erratic treatment of unlinked clusters and needs to be corrected appropriately. The basis set choice for the calculation of highly accurate values of properties is also discussed. In order to circumvent the dimensionality problem the use of basis sets with explicit dependence on the external perturbation strength is recommended and methods for their choice and optimization are presented. A particular attention is paid to the many-body perturbation theory involving singly and doubly substituted intermediate states and based on the coupled Hartree-Fock solution for the one-electron perturbation problem. Different computational aspects of this method are discussed and compared with other techniques currently in use.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230116
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  • 199
    Electronic Resource
    Electronic Resource
    Two-dimensional fully numerical solutions of molecular Schrödinger equations. I. One-electron molecules (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 309-317 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A two-dimensional fully numerical relaxation approach is presented for the electronic Schrödinger equation of linear molecules. The method is tested on the lowest σ, π, δ, and φ states of H2+ and HeH2+. About 10-figure accuracy is obtained for the orbital energies. Seven-point numerical formulas are given for first and second derivatives.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230126
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  • 200
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    Electronic Resource
    Masthead (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230201
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