Infrared intensities as a quantitative measure of intramolecular interactions. Part XXVI. Variable resonance behaviour by alkyl and substituted alkyl groups

Abstract

It is shown that long chain and some bridgehead alkyl substituents (such as adamantan-1-yl and bicyclo[2·2.2]-octan-1-yl) have greater resonance interaction with a benzene ring than methyl groups. Such substituents are also shown to be more polarisable as the electron demand of the π-system is changed. The neopentyl group shows different behaviour. The failure of adamantanyl and bicyclo-octanyl substituents to show significant enhancement of donation in the solvolysis of alkyl-substituted cumyl chlorides is thus ascribed to solvation. Studies on the resonance interaction and polarisability of some halogeno-substituted alkyl groups provide clarification of the present controversy as to their mode of action.