13C Nuclear magnetic resonance studies. XIV. Conformational effects on carbinyl carbon shieldings in cyclohexanols and derivatives

Abstract

The 13C shieldings of the alicyclic carbons bearing oxygen in several cyclohexanols, their acetates and methyl ethers depend on the orientation of the oxygen functions. The compounds examined include the cis- and trans-4-alkyl derivatives in which the alkyl groups are t-butyl,i-propyl, ethyl and methyl, as well as the 3-t-butyl isomers. The results for the parent compounds are employed for the estimation of the conformational free energies of the hydroxyl, acetoxyl, and methoxyl groups, and serve to establish that 13C magnetic resonance (c.m.r.) spectroscopy offers a new approach to conformational analysis. The data were obtained using the decoupling technique and materials containing 13C in natural abundance.