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

Abstract

Vibrational 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.

Atmospheric Fate of the CH3SOO Radical from the CH3S + O2 Equilibrium

“…The OH radical reacts with CH 3 SH by H-abstraction from either the thiol group forming the CH 3 S radical or the methyl group forming the CH 2 SH radical. The CH 3 S yield was reported to be 1.1 ± 0.2 by direct kinetics measurement and 0.87 ± 0.03 based on the H 2 O and HOD yields from experiments with deuterated species . In a recent theoretical ab initio/RRKM study, the CH 3 S yield was found to be 0.98 at 298 K and 760 Torr .…”

“…The CH 3 S yield was reported to be 1.1 ± 0.2 by direct kinetics measurement 53 and 0.87 ± 0.03 based on the H 2 O and HOD yields from experiments with deuterated species. 54 In a recent theoretical ab initio/RRKM study, the CH 3 S yield was found to be 0.98 at 298 K and 760 Torr. 55 Here, we assume a unity yield of CH 3 S from the OH + CH 3 SH reaction.…”

Oceanic emissions of dimethyl sulfide and methanethiol and their contribution to sulfur dioxide production in the marine atmosphere

“…Other studies have shown that the reaction of MeSH with OH occurs primarily at the S-H group (0.87 ± 0.03) forming CH3S•, with a minor channel of H-abstraction from the methyl group (0.13 ± 0.03) (Butkovskaya and Setser, 2021). Recent ab initio/RKKM calculations determined the CH3S• yield from MeSH + OH at 298 K and 760 torr to be 0.98 (Mai et al, 2020).…”

Oceanic emissions of dimethyl sulfide and methanethiol and their contribution to sulfur dioxide production in the marine atmosphere

“…While the bimolecular rate constants of MeSH with the primary atmospheric oxidants (OH, BrO, NO 3 , Cl) are known, there has been limited study on the reactive intermediates or yields of stable products from MeSH oxidation (Butkovskaya and Setser, 1999;Tyndall and Ravishankara, 1991). However, oxidation of MeSH by OH (Reaction R1) has been shown to produce the methyl thiyl radical (CH 3 S) at a yield of 1.1 ± 0.2 (Tyndall and Ravishankara, 1989), providing a mechanistic link to known reactions in the DMS H abstraction pathway (Reaction R1) (Barnes et al, 2006), as shown in the simplified reaction scheme in Fig.…”

“…CH 3 S production from DMS H abstraction is the major pathway for SO 2 production from DMS, and the reactions of CH 3 S are therefore well studied (Barnes et al, 2006). Other studies have shown that the reaction of MeSH with OH occurs primarily at the S−H group (0.87 ± 0.03) forming CH 3 S, with a minor channel of H abstraction from the methyl group (0.13 ± 0.03) (Butkovskaya and Setser, 2021). Recent ab initio/RKKM calculations determined the CH 3 S yield from MeSH + OH at 298 K and 760 torr to be 0.98 (Mai et al, 2020).…”