Conformational properties of 1-methyl-1-germacyclohexane: low-temperature NMR and quantum chemical calculations

Abstract

The conformational preference of the methyl group of 1-methyl-1-germacyclohexane was studied experimentally in solution (low-temperature 13C NMR) and by quantum chemical calculations (CCSD(T), MP2 and DFT methods). The NMR experiment resulted in an axial/equatorial ratio of 44/56 mol% at 114 K corresponding to an A value (A = G ax − G eq) of 0.06 kcal mol−1. An average value for ΔG e→a # = 5.0 ± 0.1 kcal mol−1 was obtained for the temperature range 106–134 K. The experimental results are very well reproduced by the calculations. CCSD(T)/CBS calculations + thermal corrections resulted in an A value of 0.02 kcal mol−1, whereas a ΔE value of −0.01 kcal mol−1 at 0 K was obtained.