Experimental and Theoretical Studies of the Reaction of the OH Radical with Alkyl Sulfides: 3. Kinetics and Mechanism of the OH Initiated Oxidation of Dimethyl, Dipropyl, and Dibutyl Sulfides: Reactivity Trends in the Alkyl Sulfides and Development of a Predictive Expression for the Reaction of OH with DMS

Williams, M. B.; Campuzano‐Jost, Pedro; Hynes, Anthony J.; Pounds, Andrew J.

doi:10.1021/jp9010668

Cited by 20 publications

(23 citation statements)

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“…Taking into account the recent experimental studies 19,28 on the DMS 1 OH reaction in the presence of O 2 and their apparent agreement with previous studies, the kinetics of this reaction seems to be well established. However, there are some features related with the analysis and interpretation of that kinetic data that still needs of theoretical discussion.…”

Section: Comparison Between Cvt Theoretical Rate Constants and Experisupporting

confidence: 75%

“…According to the conclusions obtained in a previous work 32 and maintaining the methodology used in our recent electronic structure studies, [37][38][39] the MPW1K/MG3S level of calculation has been chosen for the description of the PES. The selected MPW1K 28,42 (modified Perdew-Wang one-parameter model for kinetics) hybrid functional is based on the PerdewWang exchange functional with Adamo and Barone's modified enhancement factor and the Perdew-Wang correlation functional. MPW1K has been tested against kinetic databases, and it has shown a good compromise between cost and accuracy.…”

Section: Computational Detailsmentioning

confidence: 99%

“…This predictive expression of Williams et al is based on elementary rate values for the H-abstraction process (I) and for the adduct formation (II) and on the equilibrium constant of the reversible adduct formation directly measured in the absence of O 2 . 19 the scavenging process is said to show no isotopic dependence, whereas in the latest analysis, 28 a larger O 2 enhancement in the rate coefficient is observed for the deuterated isotopomer that the authors attribute to a somewhat different falloff behavior of the DMSÁOH and d 6 -DMSÁOH formation rate constants.…”

Section: Introductionmentioning

confidence: 96%

“…Their values confirmed the greater contribution of the addition channel in the presence of O 2 at low temperatures obtained by Williams et al The results of those last experimental studies have been incorporated in the present revision of the IUPAC Gas Kinetic Data Evaluation. 26 In several recent works, Williams et al 19,27,28 have obtained new experimental results on the overall kinetics and mechanisms of the DMS (d 6 -DMS) 1 OH reactions. In contrast to the previous studies using relative techniques, Williams et al reported direct observations of the rate coefficients based on the concentration-time behavior of the hydroxyl radical over the total pressure range 50-650 torr and the temperature range 240-300 K. The results obtained are in agreement with the predictions of Albu et al 18 In addition, the O 2 dependence of the effective rate coefficients for the DMS (d 6 -DMS) 1 OH reactions is analyzed.…”

Section: Introductionmentioning

confidence: 99%

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Variational transition‐state theory study of the rate constant of the DMS·OH scavenging reaction by O₂

2011

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The chemical tropospheric dimethyl sulfide (DMS, CH3SCH3) degradation involves several steps highly dependent on the environmental conditions. So, intensive efforts have been devoted during the last years to enhance the understanding of the DMS oxidation mechanism under different conditions. The reaction of DMS with OH is considered to be the most relevant process that initiates the whole oxidation process. The experimental observations have been explained by a two-channel mechanism consisting of a H-abstraction process leading to CH3S(O)CH3 and HO2 and an addition reaction leading to the DMS·OH adduct. In the presence of O2, the DMS·OH adduct is competitively scavenged increasing the contribution of the addition channel to the overall DMS oxidation. Recent experimental measurements have determined from a global fit that the rate constant of this scavenging process is independent of pressure and temperature but this rate constant cannot be directly measured. In this article, a variational transition-state theory calculation of the low- and high-pressure rate constants for the reaction between DMS·OH and O2 has been carried out as a function of temperature. Our proposal is that the slight temperature dependence of the scavenging rate constant can only be explained if the H-abstraction bottleneck is preceded by a dynamical bottleneck corresponding to the association process between the DMS·OH adduct and the O2 molecule. The agreement between the low-pressure and high-pressure rate constants confirms the experimental observations.

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Section: Comparison Between Cvt Theoretical Rate Constants and Experisupporting

confidence: 75%

Section: Computational Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Variational transition‐state theory study of the rate constant of the DMS·OH scavenging reaction by O₂

2011

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“…8) limitation of the photosensitizing capacity of CDOM and/or the availability of substrates for H-abstraction. Although the exact mechanism responsible for DMS photodegradation in natural waters is not well established, the OH radical is likely implicated (Bouillon and Miller, 2005;Williams et al, 2009). OH radicals in natural waters are produced from CDOM photochemistry (Mopper and Zhou, 1990) and photolysis of nitrate (Zafiriou and True, 1979) in the absence of O 2 , with an additional contribution from the (photo) Fenton reaction (Esplugas et al, 2002) in the presence of O 2 .…”

Section: Dms As a Precursor Of Chmentioning

confidence: 99%

Photomineralization and photomethanification of dissolved organic matter in Saguenay River surface water

Zhang

Xie

2015

Biogeosciences

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Abstract. Rates and apparent quantum yields of photomineralization (AQY DOC ) and photomethanification (AQY CH 4 ) of chromophoric dissolved organic matter (CDOM) in Saguenay River surface water were determined at three widely differing dissolved oxygen concentrations ([O 2 ]) (suboxic, air saturation, and oxygenated) using simulated-solar radiation. Photomineralization increased linearly with CDOM absorbance photobleaching for all three O 2 treatments. Whereas the rate of photochemical dissolved organic carbon (DOC) loss increased with increasing [O 2 ], the ratio of fractional DOC loss to fractional absorbance loss showed an inverse trend. CDOM photodegradation led to a higher degree of mineralization under suboxic conditions than under oxic conditions. AQY DOC determined under oxygenated, suboxic, and air-saturated conditions increased, decreased, and remained largely constant with photobleaching, respectively; AQY DOC obtained under air saturation with short-term irradiations could thus be applied to longer exposures. AQY DOC decreased successively from ultraviolet B (UVB) to ultraviolet A (UVA) to visible (VIS), which, alongside the solar irradiance spectrum, points to VIS and UVA being the primary drivers for photomineralization in the water column. The photomineralization rate in the Saguenay River was estimated to be 2.31 × 10 8 mol C yr −1 , accounting for only 1 % of the annual DOC input into this system.Photoproduction of CH 4 occurred under both suboxic and oxic conditions and increased with decreasing [O 2 ], with the rate under suboxic conditions ∼ 7-8 times that under oxic conditions. Photoproduction of CH 4 under oxic conditions increased linearly with photomineralization and photobleaching. Under air saturation, 0.00057 % of the photochemical DOC loss was diverted to CH 4 , giving a photochemical CH 4 production rate of 4.36 × 10 −6 mol m −2 yr −1 in the Saguenay River and, by extrapolation, of (1.9-8.1) × 10 8 mol yr −1 in the global ocean. AQY CH 4 changed little with photobleaching under air saturation but increased exponentially under suboxic conditions. Spectrally, AQY CH 4 decreased sequentially from UVB to UVA to VIS, with UVB being more efficient under suboxic conditions than under oxic conditions. On a depth-integrated basis, VIS prevailed over UVB in controlling CH 4 photoproduction under air saturation while the opposite held true under O 2 -deficiency. An addition of micromolar levels of dissolved dimethyl sulfide (DMS) substantially increased CH 4 photoproduction, particularly under O 2 -deficiency; DMS at nanomolar ambient concentrations in surface oceans is, however, unlikely a significant CH 4 precursor. Results from this study suggest that CDOM-based CH 4 photoproduction only marginally contributes to the CH 4 supersaturation in modern surface oceans and to both the modern and Archean atmospheric CH 4 budgets, but that the photochemical term can be comparable to microbial CH 4 oxidation in modern oxic oceans. Our results also suggest that anoxic microniches in particulate orga...

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Reaction kinetics and thermochemistry of the chemically activated and stabilized primary ethyl radical of methyl ethyl sulfide, CH₃SCH₂CH₂•, with O₂ to CH₃SCH₂CH₂OO•

Song

Bozzelli

2019

Int J of Chemical Kinetics

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Oxidation of methyl ethyl sulfide (CH 3 SCH 2 CH 3 , methylthioethane, MES) under atmospheric and combustion conditions is initiated by hydroxyl radicals, MES radicals, generated after loss of a H atom via OH abstraction, will further react with O 2 to form chemically activated and stabilized peroxyl radical adducts. The kinetics of the chemically activated reaction between the CH 3 SCH 2 CH 2 • radical and molecular oxygen are analyzed using quantum Rice-Ramsperger-Kassel theory for k(E) with master equation analysis and a modified strong-collision approach to account for further reactions and collisional deactivation. Thermodynamic properties of reactants, products, and transition states are determined by the B3LYP/6-31+G(2d,p), M062X/6-311+G(2d,p), B97XD/6-311+G(2d,p) density functional theory, and CBS-QB3, G3MP2B3, and G4 composite methods. The reaction of CH 3 SCH 2 CH 2 • with O 2 forms an energized peroxy adduct CH 3 SCH 2 CH 2 OO• with a calculated well depth of 34.1 kcal mol −1 at the CBS-QB3 level of theory. Thermochemical properties of reactants, transition states, and products obtained under CBS-QB3 level are used for calculation of kinetic parameters. Reaction enthalpies are compared between the methods. The temperature and pressure-dependent rate coefficients for both the chemically activated reactions of the energized adduct and the thermally activated reactions of the stabilized adducts are presented. Stabilization and isomerization of the CH 3 SCH 2 CH 2 OO• adduct are important under high pressure and low temperature.At higher temperatures and atmospheric pressure, the chemically activated peroxy adduct reacts to new products before stabilization. Addition of the peroxyl oxygen radical to the sulfur atom followed by sulfur-oxygen double bond formation and elimination of the methyl radical to form S(= O)CCO• + CH 3 (branching) is a potentially important new pathway for other alkyl-sulfide peroxy radical systems under thermal or combustion conditions. K E Y W O R D Skinetics, methyl ethyl sulfide, oxidation, thermochemistry 618

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Cited by 20 publications

References 36 publications

Variational transition‐state theory study of the rate constant of the DMS·OH scavenging reaction by O₂

Variational transition‐state theory study of the rate constant of the DMS·OH scavenging reaction by O₂

Photomineralization and photomethanification of dissolved organic matter in Saguenay River surface water

Reaction kinetics and thermochemistry of the chemically activated and stabilized primary ethyl radical of methyl ethyl sulfide, CH₃SCH₂CH₂•, with O₂ to CH₃SCH₂CH₂OO•

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Cited by 20 publications

References 36 publications

Variational transition‐state theory study of the rate constant of the DMS·OH scavenging reaction by O2

Variational transition‐state theory study of the rate constant of the DMS·OH scavenging reaction by O2

Photomineralization and photomethanification of dissolved organic matter in Saguenay River surface water

Reaction kinetics and thermochemistry of the chemically activated and stabilized primary ethyl radical of methyl ethyl sulfide, CH3SCH2CH2•, with O2 to CH3SCH2CH2OO•

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Variational transition‐state theory study of the rate constant of the DMS·OH scavenging reaction by O₂

Variational transition‐state theory study of the rate constant of the DMS·OH scavenging reaction by O₂

Reaction kinetics and thermochemistry of the chemically activated and stabilized primary ethyl radical of methyl ethyl sulfide, CH₃SCH₂CH₂•, with O₂ to CH₃SCH₂CH₂OO•