Kinetics of Hydrogen Abstraction Reaction Class H + H−C(sp3):  First-Principles Predictions Using the Reaction Class Transition State Theory

2003 ◽  
Vol 107 (8) ◽  
pp. 1138-1147 ◽  
Author(s):  
Shaowen Zhang ◽  
Thanh N. Truong
Author(s):  
Nguyen Trong Nghia

C2H5OH has been using as an alternative fuel for decades; HO2 also plays a pivotal role in the combustion. The kinetics and mechanism for the reaction between C2H5OH and HO2 radical has been investigated using the molecular parameters for the reactants, transition states and products predicted at the CCSD(T)//B3LYP/6-311++G(3df,2p) level of theory. There are ten pair products have been found including C2H5O + H2O2 (PR1), CH3CHOH + H2O2 (PR2), CH2CH2OH + H2O2 (PR3), CH3CH2OOOH + H (PR4), C2H5 + HOOOH (PR5), CH3CH2OOH + OH (PR6), CH3CH(OH)OOH + H (PR7), HOCH2CH2OH + H (PR8), HOOCH3 + CH2OH (PR9), and CH3 + HOOCH2OH (PR10) in which the second and third ones are the major channels. The rate constants and branching ratios for all H-abstraction reactions have been calculated using the conventional transition state theory with asymmetric Eckart tunneling corrections for the temperature ranging from 298 to 2000 K.


2011 ◽  
Vol 10 (05) ◽  
pp. 629-639
Author(s):  
YUE ZHANG

We present a direct ab initio dynamics study of thermal rate constants of the hydrogen abstraction reaction of H 2 Se + H → SeH + H 2. The QCISD and CCSD(T) methods were employed to optimize the geometries of stationary points and to calculate the harmonic vibrational frequencies. The split-valence 6-311 + G(d,p) and correlation-consistent cc-pVTZ basis sets big enough to describe the geometries and vibrational frequencies of the species involving in the title reaction. The energies obtained at the QCISD(T)/6-311 ++ G(3df,3pd)//QCISD/6-311 + G(d,p) level of theory is able to compare to those calculated at the CCSD(T)/6-311 ++ G(3df,3pd)//CCSD(T)/6-311 + G(d,p) level of theory. The energies of all the selected points along the minimum energy path (MEP) were refined at the QCISD(T)/6-311 ++ G(3df,3pd) level of theory. The barriers were obtained at the both QCISD(T)/6-311 ++ G(3df,3pd)//QCISD/6-311 + G(d,p) and CCSD(T)/6-311 ++ G(3df,3pd)//CCSD(T)/6-311 + G(d,p) levels of theory are in good agreement with experimental one. The forward rate constants were evaluated with both canonical variational transition state theory with small curvature tunneling correction (CVT/SCT) and improved canonical variational transition state theory with small curvature tunneling correction (ICVT/SCT) in the temperature range of 200–2500 K. The calculated forward rate constants of the reaction at the QCISD(T)/6-311 ++ G(3df,3pd)//QCISD/6-311 + G(d,p) level of theory are in good agreement with available experimental data.


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