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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 69 (1998), S. 193-200 
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The role of electron pairing in chemical bonding stressed by the Lewis electron-pair model of the chemical bond is analyzed and discussed from the point of view of the proposal that chemical bonds are the regions of space populated roughly by two electrons and which at the same time exhibit low fluctuation of an electron pair. Based on this assumption, we have been able to introduce a new localization procedure, the output of which are just the orbitals (chemical bonds) satisfying the criterion of minimum pair fluctuation. It has been shown that these orbitals remarkably well display the most important attributes of chemical bonds, namely, the localization in the regions where classical bonds are expected and there is very high transferability from one molecule to another. The applicability of this procedure as a new means of the analysis and the visualization of the molecular structure is also discussed.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 69: 193-200, 1998
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 29Si NMR subtituent chemical shifts of 14 meta-and para-substituted derivatives of phenyltrimethyl-and phenoxytrimethyl-silanes have been interpreted in a uniform manner. They are shown to depend not only on the local but also on the non-local parts of the charge distribution around the resonating nucleus. While the local part is taken into account by the paramagnetic screening constant, the influence of the non-local part can be described by the induced internal electric field and additional higher order terms.
    Additional Material: 1 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 171-176 
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The recently proposed pair population analysis was applied to the study of electron reorganization in the course of chemical reactions. The studied reactions involved a series of pericyclic reactions, both forbidden and allowed, and attention was devoted mainly to the evaluation of the specific differences between the allowed reactions and the forbidden ones. It was demonstrated that while the mechanism of allowed reactions can be visualized as a simple cyclic shift of the bonds the electron reorganization in forbidden reactions is much more complex and involves the considerable changes in the character of the wave function during the process. © 1997 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1575-1583 
    ISSN: 0192-8651
    Keywords: 1-octanol/water partition coefficient ; molecular quantum similarity measures ; atomic shell approximation ; promolecular densities ; QSAR ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A new molecular descriptor of hydrophobicity based on molecular quantum similarity measures (MQSM), which can be used to replace the log P parameter in QSAR studies, is proposed. Unlike the majority of existing approaches for calculation of log P, the present methodology does not rely on the use of fragment additive contributions, but rather it is based on the comparison of quantum chemically calculated electron density distributions of a given molecule in water and in 1-octanol, using MQSM. The method has been tested on a broad series of 58 molecules including such structural types as aliphatic hydrocarbons, alcohols, amines, halides, carboxylic acids, esters, amides, and ketones, as well as more complex systems with two functional groups. In all cases investigated, an excellent linear relationship between calculated MQSM and log P values was found. Additionally, an example of QSAR analysis is presented using MQSM instead of log P values, corresponding to predict the narcosis of tadpoles.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 1575-1583, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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