Substituent effects on the chemical shift of the hydroxy-proton of 2,6-dimethylphenols and 1-naphthols in dimethyl sulphoxide

Abstract

The chemical shifts of the hydroxy-proton of 2.6-dimethyl phenol and ten 4-substituted 2.6-dimethylphenols and of I -naphthol and nine 4-substituted 1 -naphthols have been measured for dimethyl sulphoxide solutions. Analysis of published data on the chemical shifts of phenols in dimethyl sulphoxide reveals that +M as well as -M 4-substituents exhibit enhanced resonance effects. Substituent effects in 2,6-dimethylphenols and in 1 -naphthols parallel these effects in phenols. The Hammett p values for the three series are -1.49, -1.43, and -1.55 respectively. In naphthols -M 4-substituents do not exhibit enhanced resonance effects over and above those observed in the correspondingly substituted phenols.