Electron-Stimulated Chemical Reactions in Carbon Tetrachloride/Water (Ice) Films

The electron-stimulated chemical reactions in carbon tetrachloride/water (ice) and ice films have been studied using reflection−absorption infrared spectroscopy (RAIRS) and mass spectrometry. CO2, CO, and HCl were identified as the final neutral reaction products in the electron-stimulated degradation of CCl4, while COCl2 and C2Cl4 were produced as intermediates. Molecular H2 and O2 were detected as neutral gas-phase products in the electron beam irradiation of pure ice films. Production of molecular oxygen was, however, efficiently quenched during irradiation of CCl4/H2O(ice) mixtures. A reaction mechanism is postulated based on the reactivity of the trichloromethyl (•CCl3) radical and dichlorocarbene (:CCl2) intermediates. Reactions between the trichloromethyl (•CCl3) radical and oxygen or hydroxyl radicals lead to the production of phosgene, the subsequent electron-stimulated decomposition of which produces CO or CO2. In contrast, reactions involving dichlorocarbene produce CO via hydrolysis or C2Cl4 as a result of a carbon−carbon coupling reaction.