Anomeric and conformational deuterium isotope effects in saturated sulphur and nitrogen heterocycles

Abstract

Gas phase Fourier transform i.r. and solution 500 MHz 1H n.m.r. measurements show that deuterium prefers the equatorial over the axial site in N,N′,5,5-tetramethylhexahydro[2-2H1]pyrimidine by 420 J mol–1, but exhibits no preference in the case of 5,5-dimethyl[2-2H1]-1,3-dithiane.