Rate constant and mechanism of the OH-initiated degradation of 3-penten-2-one in the atmosphere

Abstract

A systematic investigation has been performed on OH-initiated atmospheric oxidation mechanism of 3-penten-2-one (3P2) using a high-level ab initio method. The energy profile diagram information is obtained at the CCSD(T)/6-311++G(d,p)//BH&HLYP/6-311++G(d,p) + 0.9335 × ZPE levels of theory. The calculated total rate constant at 298 K using the transition state theory with tunneling corrections is found to be 3.28 × 10−11 cm3 molecule−1 s−1, which is in reasonable agreement with the experimental determination. The temperature-dependent rate constant for the reaction of 3P2 with OH radicals from 200 to 1000 K is predicted to be k = 4.44 × 10−24 × T3.9 × exp(2177/T) cm3 molecule−1 s−1. Based on mechanistic studies, our results show that acetaldehyde [CH3C(O)H], methyl glyoxal [CH3C(O)C(O)H], 2-hydroxypropanal[CH3CHOHC(O)H], peroxyacetyl nitrate CH3C(O)OONO2 (PAN), CO2, formaldehyde [HC(O)H], and CH3C(O)CHOHC(O)CH3 are the predominant products for the 3P2 + OH reaction under atmospheric conditions, which agrees closely with the experimental findings.