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Ab Initio Kinetics for Decomposition/Isomerization Reactions of C 2 H 5 O Radicals
Author(s) -
Xu Zhen Feng,
Xu Kun,
Lin Ming Chang
Publication year - 2009
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200800719
Subject(s) - chemistry , isomerization , radical , reaction rate constant , transition state theory , ab initio , rrkm theory , potential energy surface , computational chemistry , diluent , ab initio quantum chemistry methods , transition state , ground state , decomposition , thermodynamics , kinetics , molecule , atomic physics , organic chemistry , physics , quantum mechanics , catalysis
Radical reactions : The ground‐state potential energy surface of the C 2 H 5 O system is investigated by ab initio methods using optimized geometries. The rate constants for the unimolecular isomerization and decomposition reactions of the three isomeric radicals (see picture) are calculated by microcanonical transition‐state theory at 200–3000 K, varying the pressures of the diluents.The ground‐state potential energy surface of the C 2 H 5 O system, including the decomposition and isomerization of the ethoxy (CH 3 CH 2 O), 1‐hydroxyethyl (CH 3 CHOH), and 2‐hydroxyethyl (CH 2 CH 2 OH) radicals, is computed by the modified Gaussian‐2 (G2M) and CCSD(T)/6‐311+G(3df,2p) methods by using the geometries optimized at the B3LYP/6‐311+G(3df,2p) level of theory. These detailed reaction pathways are used to calculate the rate constants for the unimolecular isomerization and decomposition reactions of the three radicals by the microcanonical transition‐state theory and Rice–Ramsperger–Kassel–Marcus (RRKM) theory in the temperature range of 200–3000 K at varying pressures of He and other diluents. The predicted rate constants are in reasonable agreement with the available experimental data. In addition, the predicted heats of formation of the three isomeric radicals are compared with available experimental and theoretical values.