Carbon—Carbon Spin-Coupling Constants in Characteristic CC-Bond Types

Abstract

Carbon—carbon spin‐coupling constants have been measured for a variety of types of CC bonds (in C¹³‐enriched compounds), usually characterized by the different hybridizations of the C atoms. For hydrocarbons in which these bond types appear, the CC spin‐coupling constant is proportional to the product of the s characters of the carbon atoms forming the bond in question. For several substituted hydrocarbons ``modified s characters'' may be found, from which the spin‐coupling constants can be calculated by means of the same proportionality factor found for the hydrocarbons. The enhancement in CC spin‐coupling constant due to pi electrons seems pronounced for double and triple bonds but less so in acyclic conjugated systems. A simple correlation of CC‐bond distance and CC‐coupling constant does not exist in general, but has been found for CC single bonds in hydrocarbons.