Nuclear magnetic resonance spectroscopy. Carbon-carbon coupling

Abstract

One-bond, carbon-carbon coupling constants have been observed for several series of compounds containing ^(13)C in its natural abundance of 1.1% at both sites. The small (10-15 Hz) coupling constants in cyclopropanes show that the carbon-carbon bonds have low s character. Substituent and hybridization effects on the carbon-carbon coupling of aliphatic and alicyclic alcohols, ketones, and five- and six-membered aromatic heterocycles have been observed. Carbon-carbon couplings in methyl derivatives are proportional to carbon-proton coupling in similar bonding situations, with a slope similar to that predicted and observed by Karabatsos for the correlation of carbon-proton and proton-proton couplings. Two- and three-bond carbon-carbon coupling constants are interpreted in terms of the Fermi contact mechanism by correlations with proton-proton and carbon-proton coupling constants in similar bonding situations.