Reactivity at Low Temperature of Carbon Suboxide (C₃O₂) with Amorphous Surface of HCl Hydrates Monitored by FTIR Spectroscopy

An experimental study, monitored by FTIR spectroscopy, of the spontaneous reaction of C 3 O 2 with HCl on the acid hydrate surface has been performed at low temperature. The first appearing reaction product at 85 K was assigned to chloroformylketene while the second, appearing at 145 K, to malonyl dichloride by comparison with previously reported data in matrix isolation spectroscopy. C 3 O 2 was deposited at 80 K over an amorphous surface of HCl hydrates mainly formed from ionic species (H 3 O + (H 2 O) n - 1 Cl -; n = 1−3, 4, 6), prepared by codeposition of a H 2 O:HCl gaseous mixture at 80 K. The reactions were promoted by warming the substrate from 80 to 200 K. Experiments showed that monohydrate H 3 O + Cl - was more reactive than higher hydrates by easier C 3 O 2 protonation. Reactions are described by an ionic mechanism catalyzed by ice water and occurring on the surface. Spectral evidence of HCl amorphous hydrates, chloroformylketene, and malonyl dichloride are reported.