Reactions of OH and OD radicals with simple thiols and sulfides studied by infrared chemiluminescence of isotopic water products: Reaction OH + CH3SH revisited

Abstract

AbstractVibrational excitation of the H2O, HOD, and D2O product molecules from the reactions of OH and OD radicals with CH3SH, CH3C(O)SH, (CH3)3CSH, H2S, and CH3SCH3 was determined by modeling the infrared emission spectra using a renovated and extended set of model spectroscopic bands. Using the deuterated reactant, CH3SD, it was possible to separate spectra of abstraction from C‐ and S‐sites, which allowed measurement of branching fractions and kinetic isotope effects for individual channels. For the OH + CH3SH reaction, branching fractions of 0.13 ± 0.03 (C─H) and 0.87 ± 0.03 (S─H) were obtained. The vibrational energy released to water from abstraction of H‐atoms from the C─H and S─H sites of the reactant molecules is described. The results reported in this paper take precedence over an earlier study of CH3SH. The vibrational energy partitioning between the stretch and bend modes of water molecules from the reactions of the thiols and related reactions of H2S and CH3SCH3 are discussed. The mechanism for the OH + CH3SSCH3 reaction was confirmed to be addition followed mainly by decomposition to CH3SH and CH3SO.