Proton magnetic resonance studies of specifically deuterated cyclohexane compounds. Part II. t‐Butylcyclohexane

The preparation and PMR investigation of some specifically deuterated t‐butylcyclohexanes is reported. The chemical shifts of the various ring protons and the vicinal axial‐equatorial coupling constants have been determined accurately. The coupling constants show that an equatorial t‐butyl group distorts the chair conformation of cyclohexane: the t‐butyl side of the ring is somewhat puckered. The chemical shifts of the ring protons of t‐butylcyclohexane differ from those of cyclohexane. In consequence the use of a t‐butyl group as a holding group in conformational analysis is not always justified. A long range coupling of 1.4 Hz is observed between 1,3‐diequatorial ring protons. This partly explains the complexity of the spectra of apparently simple spin systems of other cyclohexane derivatives. The dehydration of 3‐t‐butylperdeuterocyclohexanol using D3PO4 gives rise to a mixture of the three t‐butylperdeuterocyclohexenes. The intermediate formation of a protonated four‐membered ring is proposed in order to explain the presence of deuterium in the t‐butyl group of only 1‐t‐butylperdeuterocyclohexene.