C–H activation in reactions of protonated hydrogen peroxide with propane: Remarkable regioselectivity for hydride abstraction and mechanism for acid catalyzed hydrogen exchange

Reactions between deuterium labelled alkanes and H2OOH+ have been investigated by conducting gas phase reactions within the cell of an FT-ICR mass spectrometer. Propane is exceptional in giving off a hydride (deuteride) thereby producing the propyl cation and two water molecules, as well as demonstrating high activity for proton induced H/D exchange. The detailed mechanistic scenario has been modelled using accurate quantum chemical methods (MP2 and G3). The calculations show that hydrogen exchange takes place via a synchronous flip–flop mechanism. Results of reactions with partially deuteriated propanes demonstrate quite exceptional regioselectivity for hydride abstraction in favour of the secondary positions (2-H) compared to the primary (1-H). This observation is understood on the basis of transition state theory.