The heterogeneous reaction of HCl on an ice surface, which is relevant in atmospheric and stratospheric chemistry, is discussed from a theoretical approach. A proton transfer mechanism is proposed for HCl ionization on amorphous ice surfaces leading to a solvent separated ion pair. The reactivity of ionized hydrochloric acid on carbon suboxide (C3O2) is studied as an example and in connection with our earlier experimental work. The role of the ice environment on the structure and polarization of the suboxide molecule is elucidated and a theoretical model is proposed for the synthesis of chloroformylketene.