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

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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. CO 2, CO, and HCl were identified as the final neutral reaction products in the electron-stimulated degradation of CCl 4, while COCl 2 and C 2 Cl 4 were produced as intermediates. Molecular H 2 and O 2 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 CCl 4 /H 2 O(ice) mixtures. A reaction mechanism is postulated based on the reactivity of the trichloromethyl ( • CCl 3 ) radical and dichlorocarbene (: CCl 2 ) intermediates. Reactions between the trichloromethyl ( • CCl 3 ) radical and oxygen or hydroxyl radicals lead to the production of phosgene, the subsequent electron-stimulated decomposition of which produces CO or CO 2 . In contrast, reactions involving dichlorocarbene produce CO via hydrolysis or C 2 Cl 4 as a result of a carbon−carbon coupling reaction.