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The theoretical study of temperature- and pressure-dependent reactions kinetic for unimolecular isomerization reactions of C2H5O radical

Nguyen Ngoc Tri, Nguyen Ngoc Ha

Abstract


Minimum energies for the C2H5O radical, products and transition states of reactions on the potential energy surface were obtained at the MP2/6-311++G(3df,2pd) high level of theory, and single-point energies were refined at the CCSD(T)/6-311++G(3df,2pd) level of theory for all stationary points. Isomerization reactions of C2H5O radical take place via two proton migration mechanisms: C2H5O → CH3CHOH (1,2-H shift) (1) and C2H5O → CH2CH2OH (1,3-H shift) (2). Temperature and pressure-dependent rate constants of the two reactions (1) and (2) were calculated by using transitional state theory (TST) and Rice-Ramsperger-Kassel-Marcus (RRKM) theory. Obtained results show that the reaction rate constants were: kTST(T) (1) = 1.978.1010.T0.428 exp(-13530.4/T), kTST(T) (2) = 3.077.1010.T0.403 exp(-14347.2/T); kRRKM(T) (1) = 1.664.1012.T0.204 exp(-15465.0/T), kRRKM(T) (2) = 1.183.1012.T0.147 exp(-15927.1/T) using TST and RRKM theory, respectively. The pressure-dependent rate constants of isomerization reactions being analysed and solved by RRKM theory and master equation (ME) method were k(T,P) (1) = 9.110.107.P0.815 exp(-4959.3/T) and k(T,P) (2) = 1.382.107.P0.850 exp(-5009.5/T). Our results suggest that, rate constants of both (1) and (2) depend linearly on pressure in the low-temperature and pressure ranges, or in the high-temperature range. Conversely, rate constants of both (1) and (2) are nearly not depending on pressure in the low-temperature and high-pressure ranges.

Keywords. Potential energies surface, isomerization reactions, Rice-Ramsperger-Kassel-Marcus theory.


Keywords


Potential energies surface, isomerization reactions, Rice-Ramsperger-Kassel-Marcus theory

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