Browsing by Author "Le Huyen, Trinh"

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A model study on the mechanism and kinetics for reactions of the hydrated electron with H3O+ and NH4+ ions
(2019-09-16)
Le Huyen, Trinh
;
Pham, Tien, V
;
Minh Tho Nguyen
;
Lin, M. C.
;
交大名義發表
Mechanism and kinetics of the reactions of the hydrated electron (e(aq)(-)) with H3O+ and NH4+ cations were determined using quantum chemical computations with both density functional theory (B3LYP) and wavefunction (MP2 and CCSD(T)) methods and the 6-311 + + G(3df,2p) basis set, in conjunction with a PCM method for treating structures in solution. Although both reactions occur with a hydrogen atom transfer, their mechanisms differ from each other by kinetic results. While the reaction of e(aq)(-) and H3O+ in solution is diffusion-controlled, NH4+ reacts with e(aq)(-) via a transition structure with H-tunneling. The predicted rate constants agree well with available experimental results.
Ab Initio Chemical Kinetics for Nitrogen Tetroxide Reactions with 1,1-and 1,2-Dimethylhydrazines
(1970-01-01)
Le Huyen, Trinh
;
Raghunath, Putikam
;
Lin, Ming Chang
;
交大名義發表
;
應用化學系
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 N2O4 (NTO) with H2NN(CH3)(2) and CH3NHNHCH3 hypergolic initiation reactions, the processes critical to the chemical rocket propulsion of the N2O4-hydrazine propellant systems. The reaction of N2O4 with the dimethylhydrazines (DMHZ's) can be started by the fast reaction of DMHZ's with ONONO2, taking place after the novel N2O4 -> ONONO2 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 H2NN(CH3)(2) and CH3NHNHCH3, 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 H2NN(CH3)(2) is predicted to be 3.3x10(-5) s. The results of a similar estimate for CH3NHNHCH3 is about 2 orders of magnitude longer; both estimates indicate that very effective hypergolic reactions can occur upon mixing in these systems.