Resonance and field/inductive substituent effects on the gas-phase acidities of para-substituted phenols: A direct approach employing density functional theory

Abstract

Relative gas-phase acidities of para-substituted phenols (1, Sub - C 6H4 - OH) and their ω-substituted para-alkylphenol analogs [2, Sub - (CH2)n - C6H4 - OH] were calculated at the B3LYP/6-31+G* and AMI levels of theory. The acidity of a substituted molecule of 2 is compared with that of the unsubstituted molecule of 2 to determine the field/inductive effect of the substituent on the acidity of 2. This field/inductive effect was extrapolated to n = 0, yielding the field/inductive effect of the substituent on the acidity of 1. The derived field/inductive effect in 1 was subtracted from the difference in acidity between 1 and phenol in order to determine the resonance effect of the substituent on the acidity of 1. Our results are compared with the field/inductive and resonance substituent parameters empirically derived from previous experimental solution studies. Copyright © 2004 John Wiley & Sons, Ltd.