Evaluation of DFT methods to study reactions of benzene with OH radical

Several density functional theory (DFT) methods are applied to two different reaction channels involving OH + C6H6, and the results compared with high-level ab initio calculations. The OH adds directly to one C atom in the first channel, first forming an encounter complex with the OH poised above the aromatic plane. B3LYP, BH&HLYP, and MPW1K compute an accurate estimate of the overall exothermicity, whereas M05-2X, PBE0, and PBEPBE overestimate this quantity to some degree. With the exceptions of PBEPBE and PBE0, the other methods produce an acceptable barrier to addition. All approaches except BH&HLYP correctly predict an exothermic H abstraction, although PBEPBE is too exothermic. The BH&HLYP barrier to H abstraction is too high while the MPW1K, PBE0, and B3LYP values are better, and M05-2X the best. (c) 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011