Studies of Conformational Equilibria and Equilibration by Nuclear Magnetic Resonance Spectroscopy

Abstract

Nuclear magnetic resonance spectroscopy has been extraordinarily fruitful in the study of stereochemical problems, especially those associated with conformational analysis. In reasonably favorable cases, the position of the equilibria between conformational isomers can be determined with a high degree of accuracy, and in many cases it is also possible to make measurements of rates of equilibration of such isomers as a function of temperature. The activation parameters obtained from such measurements are of special theoretical interest because the rate processes involved are not complicated by making and breaking of bonds. This, along with the well-established utility of conformational analysis in natural-product chemistry, has led to much research on conformations and conformational equilibration in a variety of acyclic and cyclic compounds.