HYDROXYL STRETCHING IN SUBSTITUTED PHENOLS - AN AM1 STUDY

Hydroxyl-stretching frequencies (nu(OH)) were estimated for a number of 4-substituted and 2,6-disubstituted phenols using the AM1 all-valence electron molecular orbital approximation. There was significant correlation between calculated and experimentally observed frequencies with better correlation observed with the gas phase as compared with dilute solution-phase values. Significant Hammett sigma-rho relationships were recorded for the 4-substituted phenols, consistent with experimental observations. The nu(OH) stretching frequency associated with the equilibrium structure of 2,6-di-t-butylphenol was calculated to be 15 cm(-1) higher than that of phenol and this increase was attributed to steric interactions that act to effectively shorten the OH bond length. (C) 1993 John Wiley & Sons, Inc.