engleski

A computational study of the nitrobenzene reduction mechanism

Lately, nitrobenzene, nitrosobenzene and their derivatives have received a significant amount of attention in modern solid-state and polymer chemistry. The identification of mechanistic pathways in the reduction of nitrobenzene is very important for the understanding of the reactivity of nitrosoaromatics. Although the available data suggests a free-radical mechanism, a detailed energetic and structural characterization of all intermediates is yet to be found. Using computational methods, we studied the reduction pathway of nitrobenzene to aniline in a protic environment. Due to the complexity of this 6e-/6H+ mechanism, a framework for direct comparison of redox and non-redox reactions was devised. ωB97-XD/may- cc-pVTZ level of theory gave the best results with the MUE of 0.75 kcal/mol when compared to experimental data. Since some reaction intermediates generated in parallel reactions (for example, from PhNO2H+ and PhNO2– to PhNO2H.) have been experimentally confirmed, all possible elementary steps were taken into the consideration. We calculated Gibbs energies of all investigated intermediates and proposed a mechanism in good agreement with experimental observations. Also, our lowest energy pathway provides an explanation for the evident difficulty in obtaining nitrosobenzene by direct reduction of nitrobenzene, as well as the lack of experimental data on reduction intermediates between hydroxyaniline and aniline.

nitrobenzene ; reduction ; DFT

nije evidentirano