Investigations of structure and conformation. Part 6. Long-range interactions and line-width alternation for γ-proton splittings in ·CH2OCH2OCH3: temperature-dependent electron spin resonance spectra

Abstract

E.s.r. spectra of ·CH₂OCH₂OCH₃ at low temperatures show line-width alternation in both the α- and the γ-proton hyperfine splitting patterns; conformational interconversion involving rotation around the O_β–C_γ bond has an energy barrier of 19 ±2 kJ mol^–1. In the radical's preferred conformation, the γ-proton splittings have opposite signs, which is understandable in terms of a combination of both hyperconjugation and through-bond spin-polarisation to spin transmission. INDO MO Calculations provide corroboration for the conformational analysis.