Ring inversion of some 5,5-dimethyl-2-spiro-1,3-dioxans

Abstract

The ring inversion of some 5,5-dimethyl-1, 3-dioxans bearing spiro substituents (cyclobutane, cyclopentane and cyclohexane) at the 2-position has been investigated by high resolution n.m.r. using the total line-shape method. The activation parameters for this process have been determined and the importance of steric syn-axial interactions in determining the height of the barrier to inversion has been confirmed. Large negative values of ΔS^≠ for the inversion process were obtained in two cases.