%0 Journal Article
%T Oxidation reaction mechanism and kinetics between OH radicals and alkyl
%A Abolfazl Shiroudi
%A Arezoo Tahan
%J Progress in Reaction Kinetics and Mechanism
%@ 1471-406X
%D 2019
%R 10.1177/1468678319832382
%X Kinetic rate constants for the oxidation reactions of OH radicals with CH3SH (1), C2H5SH (2), n-C3H7SH (3) and iso-C3H7SH (4) under inert conditions (Ar) over the temperature range 252£¿430£¿K have been studied using the CBS-QB3 composite method. Kinetic rate constants under atmospheric pressure and in the fall-off regime have been estimated using transition state theory (TST) and statistical Rice¨CRamsperger¨CKassel¨CMarcus (RRKM) theory. Comparison with experiment confirms that in the OH-addition pathways 1£¿4 leading to the related products, the first bimolecular reaction step has effective negative activation energies around £¿2.61 to 3.70 kcal mol£¿1. Effective rate coefficients have been calculated according to a steady-state analysis of a two-step model reaction mechanism. As a result of the negative activation energies, pressures larger than 104£¿bar would be required to restore to some extent the validity of this approximation for all the channels. By comparison with experimental data, all our calculations for both the OH-addition and H-abstraction reaction pathways indicate that from a kinetic viewpoint and in line with the computed reaction energy barriers, the most favourable process is the OH-addition pathway to n-C3H7SH to yield the [n-C3H7SH£¿OH]£¿ species, whereas under thermodynamic control of the bimolecular reactions (R£¿SH+OH£¿), the most abundant product derived from the H-abstraction pathway will be the [n-C3H7£¿S£¿+H2O] species
%K Aliphatic thiols
%K OH radical
%K oxidation processes
%K OH-addition
%K rate constant
%K reaction mechanism
%K TST
%K RRKM
%U https://journals.sagepub.com/doi/full/10.1177/1468678319832382