Theoretical study of the reaction mechanism between Criegee intermediates and hydroxyl radicals in the presence of ammonia and amine.

Criegee intermediates (CIs), formed in the ozonolysis process of unsaturated hydrocarbons, play an important role in the formation of OH radicals, sulfuric acid, and aerosols. In this study, quantum chemical calculations were carried out to investigate the mechanism for the reaction of Criegee intermediates [involving CHOO, CHCHOO and (CH)COO] with OH radicals at the level of CCSD(T)/jun-cc-pVTZ//M06-2X/6-311 + G(2d,2p). A third component, such as water, ammonia, or amines, was introduced to the reaction of CIs with OH to evaluate their catalytic effect. The results show that the OH addition is the favorable channel among four channels involving cis-H abstraction, trans-H abstraction and O abstraction. The third component has a positively catalytic effect on the trans-H abstraction and O abstraction pathways. Moreover, for the trans-H abstraction of CHCHOO and (CH)COO with OH, ammonia and amine exhibit more effectively catalytic ability than water. Furthermore, Born-Oppenheimer molecular dynamic simulation results show that the addition of third component to CIs and hydrogen abstraction from the third component by OH occur simultaneously.