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.

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One-electron reduction behavior of tetrachloro-o-benzoquinone has been studied theoretically and it is a good electron acceptor in various media.

The reaction mechanism between tetrachloro-o-benzoquinone and H2O2 was studied theoretically and an alternative approach to produce the hydroxyl radical was proposed.

Dissociation dynamics of the temporary negative ions of ethanol and acetaldehyde formed by the low-energy electron attachments is investigated by using the anion velocity map imaging technique and ab initio molecular dynamics simulations. The momentum images of the dominant fragments O(-)/OH(-) and CH3 (-) are recorded, indicating the low kinetic energies of O(-)/OH(-) for ethanol while the low and high kinetic energy distributions of O(-) ions for acetaldehyde. The CH3 (-) image for acetaldehyde also shows the low kinetic energy. With help of the dynamics simulations, the fragmentation processes are qualitatively clarified. A new cascade dissociation pathway to produce the slow O(-) ion via the dehydrogenated intermediate, CH3CHO(-) (acetaldehyde anion), is proposed for the dissociative electron attachment to ethanol. After the electron attachment to acetaldehyde molecule, the slow CH3 (-) is produced quickly in the two-body dissociation with the internal energy redistributions in different aspects before bond cleavages.