Atmospheric Oxidation Mechanism of 2-Hydroxy-benzothiazole Initiated by Hydroxyl Radicals

Volatile chemical products (VCPs) and their transformation mechanisms are increasingly important in assessing air quality, as regulations on the atmospheric volatile organic compounds emitted by industries and fossil fuel-powered vehicles have become more stringent. 2-Hydroxy-benzothiazole (2-OH-BTH) is an important class of VCPs, also known as a high production volume chemical, and is employed in numerous industrial and domestic products. Therefore, understanding the 2-OH-BTH’s atmospheric fate is crucial for assessing its environmental risk. In the present work, the •OH-initiated transformation mechanism and kinetics of 2-OH-BTH were explored using density functional theory calculations. The results suggest that for the reaction of 2-OH-BTH with •OH, H-abstraction is the dominant pathway. The most favorable intermediate formed from the H-abstraction pathway further goes for unimolecular C–S bond rupture to form an S-centered radical intermediate. The S-centered radical intermediate reacts with O2 to produce alkyl peroxy radicals, that mainly react with NO to form organonitrates/alkoxy radical-related products. The final formed product has a higher toxicity compared to its parent corresponding compound. The current study provides a comprehensive investigation of •OH-initiated atmospheric oxidation of 2-OH-BTH, which is valuable for understanding the transformation mechanisms and assessing its risk in the atmospheric environment.