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Published May 2013 | Supplemental Material
Journal Article Open

Experimental and quantum mechanics investigations of early reactions of monomethylhydrazine with mixtures of NO_2 and N_2O_4


The gas-phase chemistry of the hypergolic system CH_3NHNH_2 – monomethylhydrazine (MMH), with oxidizers NO_2/N_2O_4 at room temperature and 1 atm N_2 was investigated experimentally using a gold-coated chamber reactor, coupled with a Fourier transform infrared (FTIR) spectrometer. The IR-active species identified in the early reactions include HONO, monomethylhydrazinium nitrite (MMH·HONO), methyl diazene (CH_3N=NH), methyl nitrate (CH_3ONO_2), methyl nitrite (CH_3ONO), nitromethane (CH_3NO_2), methyl azide (CH_3N_3), H_2O, N_2O and NO. In order to elucidate the mechanisms by which these observed products are formed, we carried out quantum mechanics calculations [CCSD(T)/M06-2X] for the possible reaction pathways. Based on these studies, we propose that the oxidation of MMH in an atmosphere of NO_2 occurs via two mechanisms: (1) sequential H-abstraction and HONO formation, and (2) reaction of MMH with asymmetric ONONO_2, leading to formation of methyl nitrate. These mechanisms successfully explain all intermediates observed experimentally. We conclude that the formation of asymmetric ONONO_2 is assisted by an aerosol formed by HONO and MMH that provides a large surface area for ONONO_2 to condense, leading to the generation of methyl nitrate. Thus we propose that the overall pre-ignition process involves both gas-phase and aerosol-phase reactions.

Additional Information

© 2013 The Combustion Institute. Published by Elsevier Inc. Received 25 September 2012. Received in revised form 6 January 2013. Accepted 18 January 2013. Available online 15 February 2013. This material is based upon work supported by, or in part by, the U. S. Army Research Laboratory and the U. S. Army Research Office under grant number W911NF-08-1-0124. The computational facility was funded by DURIP grants from ARO and ONR.

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