Axial/equatorial proportions for 2-substituted cyclohexanones

Abstract

Axial-equatorial conformational proportions have been measured for 2-substituted cycloheranones in chloroform by the Eliel method for F, Cl, Br, I, MeO, MeS, Me 2 N, MeSe, and Me. For the first seven of these, at least five experimentally independent measurables were used and the resulting conformational preferences appear to be accurate to within 10%. Systematic errors degraded the results for MeSe and Me. For Me 2 N, the conformational preference also was measured for the first time at slow exchange in the low-temperature 13 C spectrum in several solvents. In chloroform, steric and polar effects contribute to the conformational preferences, with steric effects dominant for large groups such as I and MeS