Substituent effects in anthrasemiquinones. Part 2.—Use of additivity principles and linear correlation plots

Abstract

Electron paramagnetic resonance spectra have been obtained from 31 anthraquinones, mostly asymmetric, with methyl, hydroxyl, methoxyl, and sulfoxyl substituents. The measured hyperfine splitting constants are all assigned consistently by means of additivity principles, the assignments being at variance with recently published ones. It is shown that the additivity parameters (δ) are obtainable from linear correlation plots as the product of two parameters, one being a function of the substituent in question, and the other expressing a measure of the change that a splitting constant exhibits at a particular position.