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Relative energies, stereoelectronic interactions, and conformational interconversion in silacycloalkanes
Author(s) -
Freeman Fillmore,
Fang Christine,
Shainyan Bagrat A.
Publication year - 2004
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.20236
Subject(s) - conformational isomerism , chemistry , heptane , twist , crystallography , methyl group , stereochemistry , computational chemistry , molecule , group (periodic table) , geometry , organic chemistry , mathematics
Stereoelectronic hyperconjugative interactions, geometrical parameters, and relative energies of conformations and isomers of silacycloalkanes have been calculated at the B3LYP/6‐311+G(d,p) level of theory. The chair conformer of silacyclohexane was calculated to be 3.89, 4.82, and 5.18 kcal/mol more stable than the respective 1,4‐twist conformer, 2,5‐twist conformer, and 2,5‐boat transition state. Intrinsic reaction path (IRC) calculations connected the half‐chair transition state to the chair and 2,5‐twist conformers of silacyclohexane. The energy difference (Δ E ) between the chair conformer and the half‐chair transition state that connects the chair conformer and 2,5‐twist conformer of silacyclohexane is 5.47 kcal/mol. The chair conformer of equatorial 1‐methyl‐1‐silacyclohexane is 0.45 kcal/mol more stable than the chair conformer of axial 1‐methyl‐1‐silacyclohexane. Axial 1‐methyl‐1‐silacyclohexane is 3.53 and 4.67 kcal/mol more than its 1,4‐twist and 2,5‐twist conformers, and equatorial 1‐methyl‐1‐silacyclohexane is 3.97 and 4.82 kcal/mol more stable than its 1,4‐twist and 2,5‐twist conformers. 1‐Silabicyclo[2.2.1]heptane is 4.58 and 10.8 kcal/mol, respectively more stable than 2‐silabicyclo[2.2.1]heptane and 7‐silabicyclo[2.2.1]heptane. The influences of selectively replacing a CH 2 group in a cycloalkane with a SiH 2 group on the geometrical parameters, conformational properties, ring strain, and stereoelectronic hyperconjugative interactions are discussed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004