The variation of substituent resonance effects with electron demand
Abstract
The Hammett substituent constants for a number of substituents have been resolved into constant inductive (σI) and variable resonance (σR) contributions. Variations in σR have been interpreted in terms of changes in the demand for π electrons made on substituents and an empirical scale of ‘electron demand’ has been set up. The relationship has been tested using reactivity data, and its applications discussed.