Density functional theoretical studies on effect of intramolecular hydrogen bonds on reduction of nitrophenols

Abstract

Intramolecular hydrogen bonds(IMHBs) can lead to different physicochemical characteristics of nitrophenols(NPs) that determine their environmental behavior. In the present work, to reveal the relationship between IMHB and nitrophenol reduction, the effects of IMHB on the molecular geometries and properties of a series of nitrophenols were investigated with density functional theory(DFT) calculations. The results of the geometry optimization and atoms-in-molecules(AIM) analysis indicate relatively strong IMHBs in ortho-substituted nitrophenols, whose stability could be significantly improved. In comparing the E LUMO and adiabatic electron affinities(AEA) of the nitrophenol isomers, the presence of IMHBs benefited the reductive degradation of NPs, consistent with a previous study. To gain an insight into the effect mechanism of IMHBs on the reductive degradation behavior of these molecules, the condensed electrophilicity Fukui index(f –), natural charges and Wiberg bond orders of these nitrophenol isomers were calculated. The calculations indicate that the electrophilic reactivity activity of the O atom on the nitro group could be significantly improved due to the formation of IMHBs, which results in the enhanced reductive degradation of ortho-substituted NPs.