Electrochemical reduction of nitrotriazoles in aqueous media as an approach to the synthesis of new green energetic materials

The synthesis of new azo and azoxy compoundsvia electrochemical reduction of nitrotriazoles has been investigated in aqueous media, using nitrotriazolone (NTO) and nitrotriazole (NTr) as representative substrates. Reduction of NTO produces mainly solid azoxytriazolone (AZTO), with azotriazolone (azoTO) and aminotriazolone (ATO) as minor products, while 3-hydroxylaminotriazole is the major product formed from NTr. AZTO and azoTO are of interest as new green high-nitrogen compounds for use as insensitive high explosives (IHE). The effect of varying reaction conditions such as pH and substrate concentration has been evaluated, and a mechanism is proposed accounting for the experimental observations. In particular, the ratio of azoxy to azo in the solid product is influenced by pH and temperature, and the minor product ATO is formed not via direct reduction of NTO but via a novel thermal disproportionation reaction of the hydrazotriazolone intermediate. Conditions of high substrate concentration and low cell temperature maximise the azoxy yield and minimise the formation of minor products. Results indicate that this green electrosynthetic approach may be generally useful for the synthesis of new azoxy and azo triazoles from suitable substrates.