Alkyl substituent effects. Part 1. An analysis of alkyl inductive properties in terms of group connectivity

Abstract

Formulae are derived which express the scales of the inductive substituent constants σI and σ*, the group electronegativities χR, and the polarisability constants P of alkyl groups in terms of base-constants and ‘connectivity characteristics,’ pure numbers the value of which depend only on the number of carbon atoms a group contains and the pattern of their bonding. The formulae are of predictive value in calculating σI, σ*, χR, or P for any alkyl group and in discerning what these scale of measurement have in common and where they differ. It is shown that alkyl σ* is not a artefact as has been claimed, that σI and σ* are linear functions of alkyl group electronegativity, and that P probably has a hyperconjugative element.