Kinetic and mechanistic study of the X and XO (X = Cl, Br) reactions with dimethyl sulfoxide

Abstract

The kinetics and mechanism of the reactions of dimethyl sulfoxide (DMSO) with Cl, Br, ClO and BrO have been studied by the mass spectrometric discharge-flow method at 298 K and at a total pressure of 1 Torr of helium. The rate coefficient of the reaction Cl + DMSO ! products (1) was measured under pseudo-first-order conditions either in excess of DMSO or in excess of Cl atoms: k 1 ¼ (2.05 AE 0.35) Â 10 À11 cm 3 molecule À1 s À1 (quoted uncertainty includes estimated systematic errors). Both HCl and CH 3 were detected as products of reaction (1) and the branching ratios 0.91 AE 0.15 and 0.10 AE 0.02, respectively, were found for the channels forming these species. For the reaction Br + DMSO ! products (2) the rate constants for the HBr and CH 3 forming channels (2a and 2b, respectively) were determined from the kinetics of formation of these products: k 2a ¼ (1.1 AE 0.3) Â 10 À14 and k 2b ¼ (1.2 AE 0.3) Â 10 À15 cm 3 molecule À1 s À1 . For the reactions ClO + DMSO ! products (3) and BrO + DMSO ! products (4), only upper limits, k 3 < 1.6 Â 10 À14 and k 4 < 4 Â 10 À14 cm 3 molecule À1 s À1 , could be determined.

Oxidation of Dipropyl Thiosulfinate Initiated by Cl Radicals in the Gas Phase: Implications for Atmospheric Chemistry

“…In the case of the substitution channels, Arrhenius pre-exponential factors ( A ) of 2.00 × 10 –10 and 1.00 × 10 –11 cm 3 molecule –1 s –1 for the entrance and exit channels, respectively, were used. These A values were taken from the experimentally measured rate coefficients reported for the H-abstraction and substitution paths involved in the (CH 3 ) 2 SO + • Cl and (CH 3 S) 2 + • Cl reactions, respectively. , The aim of using these values was to ensure close agreement between the rate coefficients calculated using Mesmer, and the experimental values reported for the related analogous reactions: (CH 3 ) 2 SO + • Cl and (CH 3 S) 2 + • Cl. The modified Arrhenius parameters and activation energies for the entrance and exit channels for all the H-abstraction and substitution paths were chosen to be 0.1 and 0 kcal mol –1 , respectively.…”

Environmental effects of large igneous province magmatism: a Siberian perspective

“…The recommendation is based on a competitive kinetics study in 740 Torr air by Ballesteros et al [70]. A low-pressure discharge flow − mass spectrometry study by Riffault et al [1118], gives an upper limit that is consistent with the recommendation. The large uncertainty factor results primarily from the fact that the reported rate constant is obtained from a series of competitive kinetics experiments that are referenced to an assumed value of 3.2 x 10 −13…”

“…Br + CH 3 S(O)CH 3 . The recommendation is based on the results of a low-pressure discharge flow − mass spectrometry study by Riffault et al [1118]. These authors obtained an upper limit for the total rate constant of 1.5 x 10 −14 cm 3 molec…”

Temperature‐dependent rate constants for the reactions of chlorine atom with methanol and Br2

“…Experiments have been conducted at total pressure of 2 Torr of Helium using a conventional fast‐flow reactor combined with a molecular beam sampling electron‐impact ionization mass spectrometer 22,24‐26 . Depending on the temperature range two different flow reactors were used.…”