O—H and C—H bond dissociations in non-phenyl and phenyl groups: A DFT study with dispersion and long-range corrections

Hydrogen atom transfer is one important reaction in biological system, in industry, and in atmosphere. The reaction is preluded by hydrogen bond dissociation. To gain a comprehensive understanding on the reaction, it is necessary to investigate how the current computational methods model hydrogen bond dissociation. As a starting point, we utilized density functional theory-based calculations to identify the effect of dispersion and long-range corrections on O—H and C—H dissociations in non-phenyl and phenyl groups. We employed five different methods, namely B3LYP, CAM-B3LYP (with long-range correction), M06-2X, and B3LYP and CAM-B3LYP with the D3 version of Grimme’s dispersion. The results showed that for the case of O—H dissociation in two member of phenyl groups, namely phenol and catechol, the dispersion correction’s effect was negligible, but the long-range correction’s effect was significant. The significant effect was shown by the increasing of energy barrier and the shortening of O—H interatomic distance in the transition state. Therefore, we suggest one should consider the long-range correction in modeling hydrogen bond dissociation in phenolic compounds, namely phenol and catechol.