Reactions of Criegee Intermediates are Enhanced by Hydrogen-Atom Relay Through Molecular Design

We report a type of highly efficient double hydrogen atom transfer (DHAT) reaction. The reactivities of 3-aminopropanol and 2-aminoethanol towards Criegee intermediates (syn- and anti-CH₃CHOO) were found to be much higher than those of n-propanol and propylamine. Quantum chemistry calculation has confirmed that the main mechanism of these very rapid reactions is DHAT, in which the nucleophilic attack of the NH₂ group is catalyzed by the OH group which acts as a bridge of HAT. Typical gas-phase DHAT reactions are termolecular reactions involving two hydrogen bonding molecules; these reactions are typically slow due to the substantial entropy reduction of bringing three molecules together. Putting the reactive and catalytic groups in one molecule circumvents the problem of entropy reduction and allows us to observe the DHAT reactions even at low reactant concentrations. This idea can be applied to improve theoretical predictions for atmospherically relevant DHAT reactions.