Proton transfer reactions at the surface of ice. Heterogeneous reactions involved in stratospheric ozone depletion

Two heterogeneous reactions on an ice surface that are relevant in connection with stratospheric ozone depletion are discussed theoretically: the hydrolysis of chlorine nitrate, ClONO2, to produce HOCl and HNO3, and the acid ionization of hydrochloric acid HCl. For the former, a recently proposed proton transfer mechanism actively involving the ice lattice is supported by examination of the ClONO2 hydrolysis energetics when proton transfer is prevented. For the latter, a previously proposed picture of facile HCl ionization at, but not on, the ice surface is supported by the results of a quantum treatment of the proton and of a model investigation of the free energetics of ionization atop the ice surface.