# Kinetic and mechanistic study of the reaction between methane sulfonamide (CH 3S(O) 2NH 2) and OH

Methane sulfonamide (MSAM), inline-formulaCH3S(O)2NH2, was recently detected for the first time in ambient air over the Red Sea and the Gulf of Aden where peak mixing ratios of inline-formula≈60inline-formulapptv were recorded. Prior to this study the rate constant for its reaction with the inline-formulaOH radical and the products thereby formed were unknown, precluding assessment of its role in the atmosphere. We have studied the inline-formulaOH-initiated photo-oxidation of MSAM in air (298 inline-formulaK, 700 inline-formulaTorr total pressure) in a photochemical reactor using in situ detection of MSAM and its products by Fourier transform infrared (FTIR) absorption spectroscopy. The relative rate technique, using three different reference compounds, was used to derive a rate coefficient of inline-formula $M12inlinescrollmathml\left(normal 1.4±normal 0.3\right)×{normal 10}^{-normal 13}\phantom{\rule{0ex}{0ex}}unit{\mathrm{normal cm}}^{normal 3}\phantom{\rule{0ex}{0ex}}\mathrm{normal molec}{.}^{-normal 1}\phantom{\rule{0ex}{0ex}}{\mathrm{normal s}}^{-normal 1}$ 171pt15ptsvg-formulamathimge77641cad2fb2065a856345613e01084 acp-20-2695-2020-ie00001.svg171pt15ptacp-20-2695-2020-ie00001.png . The main end products of the photo-oxidation observed by FTIR were inline-formulaCO2, inline-formulaCO, inline-formulaSO2, and inline-formulaHNO3 with molar yields of (inline-formula0.73±0.11), (inline-formula0.28±0.04), (inline-formula0.96±0.15), and (inline-formula0.62±0.09), respectively. inline-formulaN2O and inline-formulaHC(O)OH were also observed in smaller yields of (inline-formula0.09±0.02) and (inline-formula0.03±0.01). Both the low rate coefficient and the products formed are consistent with hydrogen abstraction from the inline-formula−CH3 group as the dominant initial step. Based on our results MSAM has an atmospheric lifetime with respect to loss by reaction with inline-formulaOH of about 80 d.

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Berasategui, Matias / Amedro, Damien / Edtbauer, Achim / et al: Kinetic and mechanistic study of the reaction between methane sulfonamide (CH3S(O)2NH2) and OH. 2020. Copernicus Publications.

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