Quantum-chemical calculation of the factors determining interaction forces in monosubstituted methanes

Autor: I. F. Tupitsyn, A. Yu. Shibaev, Yu. V. Puzanov
Rok vydání: 1990
Předmět:
Zdroj: Theoretical and Experimental Chemistry. 25:378-383
ISSN: 1573-935X
0040-5760
DOI: 10.1007/bf00530428
Popis: On the basis of non-empirical calculations in the basis 3-21GF and semiempirical calculations by the MINDO/3 method we have considered the factors responsible for changes in the force constant of the CH bond (KCH) in molecules of the type CH3X (X = NH2, OH, F, Cl, CN, NC). Analysis of the “orbital strengths,” which determine the value of KCH, shows that for molecules of symmetry C3V the most important contributions come from electrons in MO of the π type. In such molecules the methyl group exhibits a hyperconjugation effect through its group of quasi-π orbitals. The qualitative picture of electronic effects on the value of KCH, obtained by resolving the total valency deformation forces into their components by the method of Fisher and Kollmar, agrees on the whole with the results obtained by treatment in terms of orbitals. It was found that in a number of methane derivatives, including molecules with CS symmetry, the value of KCH is influenced by non-valency interactions as well as by hyperconjugative effects.
Databáze: OpenAIRE
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