Rapid unimolecular reaction of stabilized Criegee intermediates and implications for atmospheric chemistry

• Published in: Nature communications Vol. 10; no. 1; pp. 2003 - 8
• Main Authors: Long, Bo, Bao, Junwei Lucas, Truhlar, Donald G.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 639/301/1034/1037; 639/638/440/950; 704/106/35/824; Atmospheric chemistry; Atmospheric models; ENVIRONMENTAL SCIENCES; Humanities and Social Sciences; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Intermediates; multidisciplinary; Organic chemistry; Oxidation; Rate constants; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-09948-7

Elucidating atmospheric oxidation mechanisms is necessary for estimating the lifetimes of atmospheric species and understanding secondary organic aerosol formation and atmospheric oxidation capacity. We report an unexpectedly fast mechanistic pathway for the unimolecular reactions of large stabilized Criegee intermediates, which involves the formation of bicyclic structures from large Criegee intermediates containing an aldehyde group. The barrier heights of the mechanistic pathways are unexpectedly low – about 2–3 kcal/mol – and are at least 10 kcal/mol lower than those of hydrogen shift processes in large syn Criegee intermediates; and the calculated rate constants show that the mechanistic pathways are 10 5 -10 9 times faster than those of the corresponding hydrogen shift processes. The present findings indicate that analogous low-energy pathways can now also be expected in other large Criegee intermediates and that oxidative capacity of some Criegee intermediates is smaller than would be predicted by existing models. Criegee intermediates have received much attention in atmospheric chemistry because of their importance in ozonolysis mechanisms. Here, using quantum mechanical kinetics, the authors reveal an unexpectedly fast mechanistic pathway for unimolecular reactions of large stabilized Criegee intermediates.