Photooxidation Reactions of Allyl Methyl Sulfide Initiated by OH Radicals and Cl Atoms in the Troposphere

The sulfur-containing volatile organic compounds (VOSCs) have a pronounced potential to impact the atmosphere. Hence, studying their photooxidation reactions with tropospheric oxidants has substantial relevance. Allyl methyl sulfide (AMS), which falls under this category, is found to be released from various sources. Hence, the present study explored the kinetics of AMS + OH and AMS + Cl reactions over 283-363 K, employing both experimental and computational methodologies. Pulsed laser photolysis─laser-induced fluorescence (PLP-LIF) technique was utilized to determine the rate coefficients of the AMS+OH reaction, whereas the kinetics of the AMS + Cl reaction were assessed using the relative rate (RR) technique, aided by gas chromatography with a flame ionization detector (GC-FID). The reaction products formed during the oxygen-assisted AMS + Cl reaction were separated and identified by gas chromatography-mass spectrometry (GC-MS). The Arrhenius expressions determined using experimental methodologies include <i>k</i>_AMS+OH(283-363 K) = (3.28 ± 1.07) × 10^-12 exp{(534 ± 104)/<i>T</i>} and <i>k</i>_AMS+Cl(283-363 K) = (9.14 ± 1.34) × 10^-11 exp{(426 ± 47)/<i>T</i>} cm³ molecule^-1 s^-1. Computational studies were performed to complement the experimental findings and confirmed the addition pathways as the major pathways in both reactions. An inverse correlation with the temperature was observed for the rate coefficients of AMS + OH and AMS + Cl reactions. At the same time, the AMS + OH reaction kinetics were found to be independent of the pressure, and a positive correlation with the pressure was revealed for the AMS + Cl reaction. Sulfur dioxide, a key product of the AMS+Cl reaction, can lead to various atmospheric issues that can cause serious human health problems.