Kinetics Study of Reaction CH3N•hNH2 + OH by multireference second-order perturbation theory and multireference coupled-cluster theory

Hongyan Sun, Chung K. Law, Karol Kowalski, Kiran Bhaskaran-Nair

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The H-abstraction reactions of monomethylhydrazine (MMH) generate four radical intermediates: CH3N•ENH2, cis-CH3NHN•EH, trans-CH3NHN•EH, and C•EH2NHNH2, which undergo further decomposition to smaller radicals and stable products. The s-scission of H atom from the CH3N•ENH2 radical is not as feasible as the s-scission of NH2 and CH3 radicals from the other three radicals due to its higher energy barrier (Sun et al., J. Phys. Chem. A, 2012, 116(33), 8419-8430). Consequently, the CH3N•ENH2 radical undergoes further oxidation reactions. Due to the strong quasi-degeneracy effect, the kinetics of CH3N•ENH2 + OH was studied in detail with application of several ab initio quantum chemistry theories. Twenty-five geometries of the stationary point of potential energy surface were investigated by using multi-reference second-order perturbation theory. The single point energies were refined by quadratic configuration interaction theory, coupled-cluster theory, locally renormalized coupled-cluster theory, and state selective multi-reference coupled-cluster theory including Brillouin-Wigner and Mukherjee•'s approaches, with single and double excitations and correction for triple excitations. For the OH addition to the central and terminal nitrogen of the CH3N•ENH2 radical, the state-averaged active space (4e,3o) consists of two degenerated p orbitals of the OH and the p orbitals of N atoms in the transition states and H-bonded complexes. For the dissociation of the CH3N(OH)NH2 and CH3NNH2(OH) adducts, a larger active space was applied. Specifically, for the OH intramolecular abstraction of methyl H, the active space consists of 10 electrons distributed in 8 orbitals: σ and π bonding and antibonding pairs of N'{N bond, σ bonding and antibonding pair of O'{H bond, the π bonding of N'{O bond, and the s orbital of central nitrogen. The predominant channel was found to be the OH addition to terminal N atom of CH3N•ENH2 with submerged energy barriers via two optical isomeric H-bonded complexes with energy of -5.73 kcal/mol; the forming CH3NNH2OH adduct decomposes via small energy barrier to trans- and cis-methyldiazene and water with exothermicity up to 75 kcal/mol. The large exothermicity and negative energy barrier of the reaction implicate its significant importance in MMH earlier ignition.

Original languageEnglish (US)
Title of host publication8th US National Combustion Meeting 2013
PublisherWestern States Section/Combustion Institute
Pages1763-1767
Number of pages5
ISBN (Electronic)9781627488426
StatePublished - Jan 1 2013
Event8th US National Combustion Meeting 2013 - Park City, United States
Duration: May 19 2013May 22 2013

Publication series

Name8th US National Combustion Meeting 2013
Volume2

Other

Other8th US National Combustion Meeting 2013
CountryUnited States
CityPark City
Period5/19/135/22/13

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Mechanical Engineering
  • Physical and Theoretical Chemistry

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    Sun, H., Law, C. K., Kowalski, K., & Bhaskaran-Nair, K. (2013). Kinetics Study of Reaction CH3N•hNH2 + OH by multireference second-order perturbation theory and multireference coupled-cluster theory. In 8th US National Combustion Meeting 2013 (pp. 1763-1767). (8th US National Combustion Meeting 2013; Vol. 2). Western States Section/Combustion Institute.