An Alternate Mechanism for the Reactions of Methylhydrazine with Dinitrogen Tetroxide

Various mechanisms have been proposed in the literature for the hypergolic reactions of methylhydrazine (MMH) and dinitrogen tetroxide (NTO). Most of these mechanisms involve radical reactions. However, experimental results obtained on the liquid-phase reactions of MMH and NTO by using high-resolution linear quadrupole ion trap/orbitrap mass spectrometry suggest that highly energetic ionic reactions play an important role in the hypergolic reactions of MMH with NTO. The elemental compositions of the detected ions were determined and their structures were explored by using tandem mass spectrometry experiments. Quantum chemical calculations indicate that the reactions of the nitrosonium and/or nitronium cations generated from NTO via the unsymmetrical NTO (UNTO) are important in explaining the hypergolic behavior of NTO with MMH. The most important reactions include the initial generation of the MMH radical cation that then reacts with the nitrate anion or nitrogen dioxide radical to form the final detected product ions.