Ultrasonic relaxation and ring inversion associated with chair to chair and twist-boat to chair conformational changes in 1,3-dioxans

Abstract

Ultrasonic relaxations observed in a number of alkyl-substituted 1,3-dioxans have been attributed to the perturbation of conformational equilibria involving chair to chair and twist-boat to chair isomerizations. From the temperature-dependence of the relaxation times the activation-energy parameters have been derived. In four symmetrical derivatives of 1,3-dioxans, the results have been combined with some n.m.r. data to yield the first estimates of the relative energy of the twist-boat conformer directly from experimental data.