Computational study of the catalytic synthesis of 5‐nitro‐1,2,4‐triazol‐3‐one

Abstract

In this study, 5-nitro-1,2,4-triazol-3-one (NTO) was theoretically synthesized from urea via chlorination followed by amination, formylation, and nitration under aqueous and gaseous environments based on experience of experimental methods, and metal chlorides and metal oxides were used as catalysts to promote reaction. Reaction routes closely related to experimental processes were successfully constructed, and the corresponding energy barriers were estimated for each elementary reaction. Reaction conditions distinct from those reported in the literature (including the adoption of aluminum chloride, ferric chloride, aluminum oxide, ferrous oxide, and chromium oxide catalysts, the use of nitric acid and dinitrogen pentoxide as nitration agents, and adjustment of the reaction temperature) were used in corresponding reaction systems, and the modeling results suggested that ferric chloride is a good catalyst for the chlorination reaction, ferrous oxide is suitable for catalyzing amination, formylation, and nitration, and nitric acid is the better agent for nitration. Estimates of the comparable energy barriers for each reaction stage were considered to imply more feasible pathways for NTO synthesis.

Density functional theory study on the reaction of triazol-3-one with nitronium: direct nitration versus acidic group-induced nitration

“…As a result of above ndings, the NO 3 À -induced and HSO 4 Àinduced processes (path Bn and Bs) associated with the synthesis of NTO in concentrated nitric acid and nitric-sulfuric acids are much more favorable than path A due to their obviously positive effects on reducing the nitration barriers. Therefore, in view of the barrier height of 29.8 kcal mol À1 in the nitration of TO using HNO 3 as the nitration reagent calculated at the B3LYP/6-31G(d,p) level, 21 and the results in the present paper, it is concluded that the nitration of TO in nitric-sulfuric acids is the most favorable one, which follows the path Bs in the HSO 4…”

“…35 The geometries of reactant complexes, transition states, and products were optimized using DFT-B3LYP method in conjugation with the 6-311G(d,p) basis set, 36,37 which has been widely used of in the similar system. 21,[38][39][40] At the same level of theory, vibrational frequencies were calculated on all the obtained structures to verify whether they are transition structures or local minima, to provide the zero-point vibrational energy (ZPE) and to determine the thermodynamic contributions to the enthalpy and free energy. Moreover, intrinsic reaction coordinate (IRC) 41 analysis was carried out for each transition state so as to ensure that the desired reactant and product are connected to the transition structure obtained.…”

“…It was shown that the concentration of the nitric acid used plays an extremely important role during the nitration of TO in a concentrated nitric acid system. Cheng et al 21 proposed the nitration mechanism of TO in nitric acid and dinitrogen pentoxide (N 2 O 5 ), which were used as the nitration reagents. Nevertheless, the nitration mechanism of TO in concentrated nitric acid or in nitric-sulfuric acids has never been reported so far.…”