Insights into the Reaction Mechanism of Criegee Intermediate CH₂OO with Methane and Implications for the Formation of Methanol

Abstract

Criegee intermediates (CIs) play a key role in controlling the atmospheric budget of hydroxyl radical, organic acids, and secondary organic aerosols. In this study, the detailed reaction mechanisms of the simplest Criegee intermediate CHOO and its derivatives with methane (CH) have been systematically investigated theoretically. Two pathways A and B have been identified for the title reaction. In pathway A, CIs can act as an oxygen donor by inserting its terminal oxygen atom into the C-H bond of alkanes, resulting in the formation of alcohol species. The corresponding energy barriers ranging from 6.5 to 24.1 kcal/mol are associated with the O-O bond strength of CIs. Meanwhile, this pathway is more favorable thermodynamically, where the free energy changes (enthalpy changes) range from -81.1 (-78.3) to -110.9 (-109.0) kcal/mol, respectively. In pathway B, an addition reaction to produce the hydroperoxides occurs, accompanying the hydrogen transfer from the alkanes to the terminal oxygen atom of CIs. The corresponding energy barriers ranging from 17.3 to 30.9 kcal/mol are higher than those in pathway A. Further calculations of the rate constants suggest that pathway A is the most favorable reaction channel and the rate constant exhibits a positive temperature dependence. In addition, the conformation-dependent reactivity for the title reaction has been observed. The present findings can enable us to better understand the potential reactivity of CIs in the presence of the alkane species.

Theoretical insights into the reaction mechanisms between 2,3,7,8-tetrachlorodibenzofuran and the methylidyne radical

“…Nowadays, the density functional theory (DFT) method has been widely applied in computational chemistry since its reliability and efficiency in predicting the geometries and properties has been veried by a lot of studies including the CH radical. [30][31][32][33][34][46][47][48][49][50][51][52][53][54][55][56][57] Therefore, all the species in the whole reactions have been fully optimized at the B3LYP/6-311++G** level of theory. Subsequently, vibrational frequency analysis has been performed at the same level of theory to identify the nature of the optimized structures.…”

Theoretical Investigations on the Reactivity of Hydrogen Peroxide toward 2,3,7,8-Tetrachlorodibenzo-p-dioxin

“…All the geometries have been fully optimized at the B3LYP/6-311++G(d,p) level of theory, where the reliability of the method has been verified by numerous systems [ 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. Subsequently, vibrational frequency analysis has been carried out to identify the nature of the optimized species.…”

Theoretical Insights into the Electron Capture Behavior of H2SO4···N2O Complex: A DFT and Molecular Dynamics Study

“…In this study, full geometric optimizations were performed employing the B3LYP and M06-2X methods as well as the 6-311++G(3df,3pd) basis set, where the reliability of the DFT method has been confirmed by many systems [ 24 , 25 , 26 , 27 , 28 , 29 ]. As a result, it was found that both methods can give consistent results for the geometry and energy parameters overall.…”