Heterocyclic analogs of phenol as novel potential antioxidants

Five density functional theory (DFT) methods including B3LYP, B3PW91, MPW1K, MPWB, TPSS1KCIS have been evaluated by comparing with the experimental OH bond dissociation enthalpies (BDEs) of substituted phenols. B3PW91 is found to be the best method, for which the calculation error was 3.62 kJ/mol. Subsequently, the BDEs (OH) of hydroxyl groups on five- and six-membered heteroatomic aromatic rings have been calculated using the (RO)B3PW91/6-311++G(2df,2p)//(U)B3LYP/6-311g(d,p) procedure. In addition, the ionization energy (IE) and proton affinity [PA(O−)] of these compounds have also been examined. On the basis of our theoretical study, a series of imidazolols, thiazolols, and oxazolols were studied to assess their antioxidant activities. It was found that 5-oxazolol could be a promising novel antioxidant precursor. Copyright © 2009 John Wiley & Sons, Ltd.