Formation pathways of DMSO2 in the addition channel of the OH-initiated DMS oxidation: A theoretical study

✍ Scribed by Juan M. Ramírez-Anguita; Àngels González-Lafont; José M. Lluch

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 451 KB
• Volume: 30
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.21168

✦ Synopsis

Abstract

The production of dimethyl sulfoxide (DMSO) and dimethyl sulfone (DMSO~2~) in the dimethyl sulfide (DMS) degradation scheme initiated by the hydroxyl (OH) radical has been shown to be very sensitive to nitrogen oxides (NO~x~) levels. In the present work we have explored the potential energy surfaces corresponding to several reaction pathways which yield DMSO~2~ from the CH~3~S(O)(OH)CH~3~ adduct [including the formation of CH~3~S(O)(OH)CH~3~ from the reaction of DMSO with OH] and the reaction channels that yield DMSO or/and DMSO~2~ from the CH~3~S(O~2~)(OH)CH~3~ adduct are also studied. The formation of the CH~3~S(O~2~)(OH)CH~3~ adduct from CH~3~S(OH)CH~3~ (DMS‐OH) and O~2~ was analyzed in our previous work. All these pathways due to the presence of NO~x~ (NO and NO~2~) and also due to the reactions with O~2~, OH and HO~2~ are compared with the objective of inferring their kinetic relevance in the laboratory experiments that measure DMSO~2~ (and DMSO) formation yields. In particular, our theoretical results clearly show the existence of NO~x~‐dependent pathways leading to the formation of DMSO~2~, which could explain some of these experimental results in comparison with experimental measurements carried out in NO~x~‐free conditions. Our results indicate that the relative importance of the addition channel in the DMS oxidation process can be dependent on the NO~x~ content of chamber experiments and of atmospheric conditions. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009