Atmospheric oxidation chemistry of 1-methoxy 2-propyl acetate initiated by OH radicals: kinetics and mechanisms

• Published in: Molecular physics 2020-01, Vol.118 (2)
• Main Authors: Du, Benni, Zhang, Weichao
• Format: Article
• Language: English
• Subjects: 1-methoxy 2-propyl acetate; Acetic acid; Anhydrides; Mathematical analysis; Methyl formate; OH radicals; Organic chemistry; Oxidation; Radicals; rate constant; Rate constants; Reaction kinetics; reaction mechanism; Temperature dependence; transition state theory
• ISSN: 0026-8976; 1362-3028
• DOI: 10.1080/00268976.2019.1601786

Kinetics and mechanism of the gas-phase reaction of CH 3 C(O)OCH(CH 3 )CH 2 OCH 3 (MPA) with OH radicals in the presence of O 2 and NO have been investigated theoretically by performing a high and reliable level of theory, viz., CCSD(T)/6-311 + G(d,p)//BH&HLYP/6-311++G(d,p) + 0.9335×ZPE. The calculations predict that the H-abstraction from the −CH 2 −O− position of MPA is the most facile channel, which leads to the formation of the corresponding alkoxy radicals CH 3 C(O)OCH(CH 3 )C(O *)HOCH 3 under atmospheric conditions. This activated radicals CH 3 C(O)OCH(CH 3 )C(O *)HOCH 3 will undergo further rearrangement, fragmentation and oxidative reactions and predominantly leads to the formation of various products (methyl formate HC(O)OCH 3 and acetic anhydride CH 3 C(O)OC(O)CH 3 ). In the presence of water, acetic anhydride can convert into acetic acid CH 3 C(O)OH via the hydrolysis reaction. The calculated total rate constants over the temperature range 263-372 K are used to derive a negative activation energy (E a = −5.88 kJ/mol) and an pre-exponential factor (A = 1.78×10 −12 cm 3 molecule −1 s −1 ). The obtained Arrhenius parameters presented here are in strong agreement with the experimental values. Moreover, the temperature dependence of the total rate constant over a temperature range of 263−1000 K can be described by k = 5.60 × 10 −14 ×(T/298 K) 3.4 ×exp(1725.7 K/T) cm 3 molecule −1 s −1 .