| Abstract
| - The molecular structure of 1-methyl-1-silacyclohexane 3 has been determined by gas electrondiffraction (GED). The conformational preference of the methyl group was studied experimentallyin the gas phase (GED) and in solution (low-temperature 13C NMR) and by quantum chemicalcalculations (HF, MP2, and B3LYP with 6-31G* basis sets and mPW1PW91/6-311G(2df,p)). Bothexperimental methods result in a preference of the equatorial position of the methyl group, 68(7)%in the gas phase at 298 K and 74(1)% in solution at 110 K. The calulations predict 68−73% equatorialconformer at room temperature. From coalescence temperatures, Gibbs free energies of activationfor ring inversion ΔG⧧ (eq → ax) = 5.81(18) and ΔG⧧ (ax → eq) = 5.56(18) kcal mol-1 were derived.The calculated values for ΔG⧧ (eq → ax) are 5.92 (B3LYP) and 5.84 kcal mol-1 (mPW1PW91).
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