13C nuclear magnetic resonance spectra of methoxycyclohexane derivatives. Rotamer populations about C–OMe bonds as indicated by 13C chemical shifts of methoxy- and ring-carbons and 3JC,H coupling constants

Abstract

Methoxy ¹³C chemical shifts in methoxycyclohexane derivatives may be rationalized in terms of rotamer populations about the C–OMe bond and δ₁-effects caused by steric interaction of the methoxy-group with substituents at the neighbouring 2- and 6-positions. Information on rotamer populations is obtained also from the ¹³C chemical shifts of C-2 and C-6, and from the three-bond coupling between the proton at C-1 and the methoxy-carbon atom.