Selective deuteration illuminates the importance of tunneling in the unimolecular decay of Criegee intermediates to hydroxyl radical products.

ABSTRACT: Ozonolysis of alkenes, an important nonphotolytic source of hydroxyl (OH) radicals in the atmosphere, proceeds through unimolecular decay of Criegee intermediates. Here, we report a large kinetic isotope effect associated with the rate-limiting hydrogen-transfer step that releases OH radicals for a prototypical Criegee intermediate, CH₃CHOO. IR excitation of selectively deuterated syn-CD₃CHOO is shown to result in deuterium atom transfer and release OD radical products. Vibrational activation of syn-CD₃CHOO is coupled with direct time-resolved detection of OD products to measure a 10-fold slower rate of unimolecular decay upon deuteration in the vicinity of the transition state barrier, which is confirmed by microcanonical statistical theory t

SUBMITTER: Green AM 

PROVIDER: S-EPMC5703325 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature