Kinetic and mechanistic study of the reaction between methane sulfonamide (CH<sub>3</sub>S(O)<sub>2</sub>NH<sub>2</sub>) and OH

Abstract

Abstract. Methane sulfonamide (MSAM), CH3S(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 ≈60 pptv were recorded. Prior to this study the rate constant for its reaction with the OH radical and the products thereby formed were unknown, precluding assessment of its role in the atmosphere. We have studied the OH-initiated photo-oxidation of MSAM in air (298 K, 700 Torr 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 (1.4±0.3)×10-13cm3molec.-1s-1. The main end products of the photo-oxidation observed by FTIR were CO2, CO, SO2, and HNO3 with molar yields of (0.73±0.11), (0.28±0.04), (0.96±0.15), and (0.62±0.09), respectively. N2O and HC(O)OH were also observed in smaller yields of (0.09±0.02) and (0.03±0.01). Both the low rate coefficient and the products formed are consistent with hydrogen abstraction from the −CH3 group as the dominant initial step. Based on our results MSAM has an atmospheric lifetime with respect to loss by reaction with OH of about 80 d.

Theoretical Study of the Atmospheric Chemistry of Methane Sulfonamide Initiated by OH Radicals and the CH3S(O)2N•H + 3O2 Reaction

“…Also, the NO 3 radical cannot readily form a PRC with the S-atom of MSAM due to steric hindrance. It was further reported that photolysis of MSAM as a mechanism of removal is negligible under tropospheric conditions . Therefore, the atmospheric fate of MSAM mostly depends on its reaction with • OH.…”

“…Other important sulfur compounds in the marine atmosphere include dimethyl sulfoxide, dimethyl sulfone, methyl sulfonic acid, and methyl sulfinic acid . The fates of these compounds in their reactions with OH radicals have been reported, and their atmospheric lifetimes with respect to OH radicals are estimated to range from hours to several weeks. , In addition to the sulfur compounds, nitrogen-containing molecules are also present in ocean atmospheres. Various studies have reported that organic and inorganic forms of nitrogen, such as amines (R–NH 2 ), nitrous oxide (N 2 O), and ammonia (NH 3 ), are emitted from highly biologically active upwelling regions of the oceans. − These studies reveal that sulfur- and nitrogen-containing trace compounds are present in ocean atmospheres and that they may strongly influence the global sulfur and nitrogen cycles. ,− …”

“…A reaction mechanism was proposed based on the results of numerical simulations and time-dependent formation of the end products. In summary, the results suggested that the MSAM + • OH reaction proceeds with hydrogen abstraction from the −CH 3 (methyl) group as the dominant initial step . The atmospheric lifetime of MSAM with respect to its reaction with the OH radical was reported to be about 80 days …”

A new marine biogenic emission: methane sulfonamide (MSAM), dimethyl sulfide (DMS), and dimethyl sulfone (DMSO<sub>2</sub>) measured in air over the Arabian Sea

“…Due to the low NO x of the remote marine atmosphere, this pathway seems unlikely as well. There are speculations about a possible formation from the initially formed OH-DMS adduct by O 2 addition and a subsequent complex process which is not yet fully understood (Berndt and Richters, 2012;Arsene et al, 1999;Turnipseed et al, 1996;Barnes et al, 2006).…”

Reaction between CH<sub>3</sub>C(O)OOH (peracetic acid) and OH in the gas-phase: A combined experimental and theoretical study of the kinetics and mechanism

“…Reference spectra for CH3C(O)OOH and CH3C(O)OH were obtained with the Bruker Vector 22 coupled to two further IRabsorption cells. These were a 44.39 L cylindrical quartz chamber equipped with a White-type, multiple-reflection mirror system with an 86.3 m optical path and external (HgCdTe) detector at liquid-N2 temperature (Berasategui et al, 2020;Bunkan et al, 2018) and a 570 mL glass cell with a 15 cm optical path, located in the internal optical path of the FTIR using an internal DTGS detector. The pressure in both absorption cells was monitored using 1000 or 100 Torr capacitance manometers.…”