In silico study on the mechanism of formation of hydrazine and nitrogen in the reactions of excess hydroxylamine with 2,4-dinitrophenyl diethyl phosphate

Abstract

We have examined the mechanism of unexpected formation of hydrazine and nitrogen gas from excess of hydroxylamine in 2,4-dinitrophenyl diethyl phosphate (phosphate triester) reaction using post-Hartree–Fock quantum chemical calculations. The MP2/6-31G(d) calculated results show that the formation of hydrazine and nitrogen gas initiates with the attack of the nitrogen atom of hydroxylamine to the nitrogen center of hydroxylamine-O-phosphate ester. The more reactive oxygen center of hydroxylamine is less preferential in this case to initiate the formation of hydrazine and nitrogen gas while attacking the hydroxylamine-O-phosphate ester. Interestingly, the dehydration of the hydroxylhydrazine intermediate to form diimide is catalysed by the water molecules. Further, the cyclic hydrogenation of two moles of cis-diimide leads to formation of stable hydrazine and nitrogen gas via a four-membered cyclic transition state (TS4) with small activation barrier 1.0 kcal mol⁻¹.