The proton magnetic resonance spectra and conformations of “trans”-2,3-dihalogeno-1,4-dioxans

Abstract

The A₂B₂ and ¹³C-satellite proton magnetic resonance spectrum of “trans”-2,3-dichloro-1,4-dioxan, m. p. 30°, has been analysed, and shows that the chair form of the dioxan ring is deformed as a solute or in the liquid phase as well as in the solid state. “trans”-2,3-Dibromo-1,4-dioxan has, apparently, the same molecular conformation as the dichloro-compound. The “anomeric” effect plays an important part in assisting the α-carbon–halogen bonds to adopt axial dispositions on a dioxan chair. A similar effect can be foreseen for analogous sulphur-containing compounds.