H-X (X = H, CH, CHF, CHF, CF, and SiH) Bond Activation by Criegee Intermediates: A Theoretical Perspective.

Using theoretical calculations and Born-Oppenheimer molecular dynamics simulations, it is shown here that Criegee intermediate, which is principally produced in the olefin ozonolysis, can activate H-X (X = H, CH, CHF, CHF, CF, and SiH) under mild conditions, a reaction that has long been known for transition metals. The zwitterionic electronic structure of Criegee intermediate makes it an interesting metal-free system for activating enthalpically strong small molecules such as H, methane, silanes, and boranes. The calculated barriers for the H or SiH reactions of CHOO are significantly lower than those for the CH or its fluorinated analogue reactions. The distortion-interaction energy model is found to be successful in explaining the differential reactivity of the Criegee intermediate toward activating the various H-X bonds. The canonical transition state theory calculations suggest that the CHOO-H reaction is 9-11 orders of magnitude faster than the CHOO-CH reaction over the 200-300 K temperature range. Considering that the laboratory synthesis of Criegee intermediate is now feasible, these findings may open up new vistas in the metal-free activation of small molecules.