Ab Initio Chemical Kinetics of Key Processes in the Hypergolic Ignition of Hydrazine and Nitrogen Tetroxide

Abstract

Kinetics and mechanisms of key processes leading to the hypergolic ignition of N2H4 and N2O4 have been studied by high-level ab initio molecular orbital theory in conjunction with statistical theory calculations. The results of this work suggest that the explosion following the contact of N2H4 and N2O4 in liquid or gaseous state at low temperatures can be initiated by the rapid reaction of N2H4 with ONONO2 isomers of N2O4 producing H2NN(H)NO+HNO3 without thermal activation accompanying with 21 kcal mol(-1) exothermicity. The HNO3 thus formed can instantaneously produce [N2H5+]NO3-] salt releasing twice as much acid base neutralization energy to enhance NO2 and N2H3 radical production. The thermochemistry and rate constants for reactions of species involved (NO2, NO3, N2O4, and its isomers, OH and N2Hx,(x= 2, 3, and 4)) in the chain initiation and propagation have been predicted and compared with available data in the literature.