The O–H bond dissociation enthalpies (BDE) of various substituted phenol derivatives were determined using the ONIOM(ROB3LYP/6-311++G(2df,2p):PM6) approach. Computed BDE(O–H)s of all phenol derivatives were in good agreement with available experimental values, and also well correlated with the Hammett constants, σp. It is found that the strong electron-donating NH2 and N(CH3)2 substituents induce a significant decrease in the BDE(O–H)s. On the contrary, the strong electron withdrawing NO2 and CF3 groups result in an increase in BDE(O–H)s.
