Kinetics and Reactivity Trend of Criegee Intermediates

Abstract:

Ozonolysis of alkenes produces very reactive carbonyl oxides (also called Criegee intermediates, CIs). CIs are thought to play roles in atmospheric chemistry, including formation of OH radicals and reaction with SO₂, inorganic and organic acids, water, etc. (Lin & Chao, 2017). Owing to very short lifetime and thus low steady-state concentration of CIs, it is hard to directly detect CIs in ozonolysis experiments. A new photolytic preparation of CIs (Taatjes et al., 2013) allows us to direct monitor CIs in real time via its strong UV absorption. Kinetics and UV-Vis spectroscopy of a few CIs, including formaldehyde oxide, acetaldehyde oxide, acetone oxide, methyl vinyl ketone oxide and methacrolein oxide have been investigated. Some interesting trends have been found in their reactivity. In this talk, an overview of the above CIs will be discussed, including the following issues. (i) The reactivity of CIs has strong structure dependence (for example, anti-CH₃CHOO reacts quickly with water but syn-CH₃CHOO does not) (Lin & Chao, 2017). (ii) The atmospheric fates of different types of CIs are, thus, different. (iii) Water may catalyze CI reactions. An analysis method (Chao et al., 2019) has been proposed to predict the efficiency of water catalysis.

References:

Chao, W., Yin, C., Takahashi, K., & Lin, J. J.-M. (2019). Hydrogen-Bonding Mediated Reactions of Criegee Intermediates in the Gas Phase: Competition between Bimolecular and Termolecular Reactions and the Catalytic Role of Water. J. Phys. Chem. A 123(39), 8336-8348.

Lin, J. J.-M., & Chao, W. (2017). Structure-dependent reactivity of Criegee intermediates studied with spectroscopic methods. Chem. Soc. Rev. 46(24), 7483-7497.

Taatjes, C. A., Welz, O., Eskola, A. J., Savee, J. D., Scheer, A. M., Shallcross, D. E., Rotavera, B., Lee, E. P. F., Dyke, J. M., Mok, D. K. W., Osborn, D. L., & Percival, C. J. (2013). Direct Measurements of Conformer-Dependent Reactivity of the Criegee Intermediate CH₃CHOO. Science, 340(6129), 177-180.