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  • Theoretical, Physical and Computational Chemistry  (3)
  • Functional groups  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 93 (1996), S. 165-176 
    ISSN: 1432-2234
    Keywords: Group valence ; Functional groups ; Multicenter bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The quantum chemical definition of valence as a property of an atom in a molecule was generalized to functional groups in molecules. The new definition was applied to a series of functional groups in simple organic molecules. The results were found to be in agreement with expectation on the basis of classical valence rules. CH2, N2 and CO group valences in selected organic molecules are compared. Group valences for systems violating the classical valence rules are also briefly discussed with an emphasis on the role of multicenter bonding in the phenomenon of hyper- and subvalence. Finally, Si2 groups serve to probe the bulk character of small and medium silicon clusters.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretica chimica acta 93 (1996), S. 165-176 
    ISSN: 0040-5744
    Keywords: Key words: Group valence ; Functional groups ; Multicenter bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract.  The quantum chemical definition of valence as a property of an atom in a molecule was generalized to functional groups in molecules. The new definition was applied to a series of functional groups in simple organic molecules. The results were found to be in agreement with expectation on the basis of classical valence rules. CH2, N2 and CO group valences in selected organic molecules are compared. Group valences for systems violating the classical valence rules are also briefly discussed with an emphasis on the role of multicenter bonding in the phenomenon of hyper- and subvalence. Finally, Si2 groups serve to probe the bulk character of small and medium silicon clusters.
    Type of Medium: Electronic Resource
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  • 3
    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.
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  • 4
    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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  • 5
    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.
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