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Ab Initio Chemical Kinetics for Nitrogen Tetroxide Reactions with 1,1‐ and 1,2‐Dimethylhydrazines
Author(s) -
Le Huyen Trinh,
Raghunath Putikam,
Chang Lin Ming
Publication year - 2020
Publication title -
propellants, explosives, pyrotechnics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.56
H-Index - 65
eISSN - 1521-4087
pISSN - 0721-3115
DOI - 10.1002/prep.201900426
Subject(s) - isomerization , chemistry , kinetics , chemical kinetics , propellant , transition state , chemical reaction , reaction mechanism , ab initio , thermodynamics , computational chemistry , organic chemistry , catalysis , quantum mechanics , physics
This work employed the quantum‐chemical method at the CCSD(T)/6‐311+G(3df,2p)//B3LYP/6‐311+G(3df,2p) level to study the mechanisms and kinetics of N 2 O 4 (NTO) with H 2 NN(CH 3 ) 2 and CH 3 NHNHCH 3 hypergolic initiation reactions, the processes critical to the chemical rocket propulsion of the N 2 O 4 ‐hydrazine propellant systems. The reaction of N 2 O 4 with the dimethylhydrazines (DMHZ's) can be started by the fast reaction of DMHZ's with ONONO 2 , taking place after the novel N 2 O 4 →ONONO 2 transformation with each of DMHZ's as a spectator within the NTO‐DMHZ collision complexes, through loose, roaming‐like transition states during the bimolecular encounters. The barriers for such isomerization processes were found to be 7.2 and 9.9 kcal/mol for H 2 NN(CH 3 ) 2 and CH 3 NHNHCH 3 , respectively. The kinetics of these reactions have been computed in the temperature range 200–2000 K; the results indicate that under the ambient temperature and pressure condition, the half‐life of NTO in the presence of an excess amount of H 2 NN(CH 3 ) 2 is predicted to be 3.3×10 −5 s. The results of a similar estimate for CH 3 NHNHCH 3 is about 2 orders of magnitude longer; both estimates indicate that very effective hypergolic reactions can occur upon mixing in these systems.