Atmospheric insight into the reaction mechanism and kinetics of isopropenyl methyl ether (i-PME) initiated by OH radicals and subsequent oxidation of product radicals

Studies on primary gas-phase reactions of emitted saturated and unsaturated ethers with oxidants and subsequent secondary reactions of product radicals with O-2 in the presence of NO are important in their atmospheric chemical processes. To accomplish these findings, we have examined the chemistry of OH-initiated oxidation of isopropenyl methyl ether (i-PME) CH3C(CH2)OCH3 by electronic structure ca using density functional theory. Our energetic calculations show that OH additions to carbon-carbon double bonds of i-PME are more favorable reaction pathways than H-abstraction reactions from the various CH sites of the titled molecule. The rate constant values which are obtained from the transition state theory also signify that OH-addition reactions have faster reaction rates than H-abstraction reactions. Our calculated total rate constant of the reaction is found 9.90 x 10(-11) cm(3) molecule(-1) s(-1). The percentage branching ratio calculations imply that OH-addition reactions have 98.09% contribution in the total rate constant. The atmospheric lifetime of i-PME is found to be 2.8 h. Further, we have identified 2-hydroxy-2-methoxypropanol, methyl acetate, methy-1,2-hydroxyacetate and 1-hydroxypropane-2-one, 1,2-dihydroxypropan-2-yl format, 2-hydroxyacetic acid, acetic acid, and formaldehyde from the secondary oxidation of product radicals.

Automated summary

The study investigated the primary gas-phase reactions of emitted saturated and unsaturated ethers with oxidants and secondary reactions of product radicals with O-2 in the presence of NO. The research focused on the OH-initiated oxidation of isopropenyl methyl ether (i-PME) using density functional theory, revealing that OH-addition reactions are more favorable and have faster reaction rates compared to H-abstraction reactions. The total rate constant of the reaction and the branching ratio were calculated, and the products from the secondary oxidation were identified.