A study of the heterogeneous reaction between dinitrogen pentaoxide and chloride ions on low-temperature thin films

Article abstract of DOI:10.1021/jp993763l

When low-temperature thin films of either ionic or covalent dinitrogen pentaoxide, N₂O_5, are exposed to gaseous HCl and water, the only products observed in the solid phase by reflection - absorption infrared spectroscopy (RAIRS) are molecular nitric acid and the oxonium ion. Nitryl chloride, ClNO_2, is not detectable. When dinitrogen pentaoxide is co-deposited with hydrogen chloride and water at 85 K and annealed to 140 K, the resultant RAIR spectra indicate that the film is composed of H₃O⁺Cl^-, N₂O₅, HNO_3, and D_2h-N₂O₄. When nitryl chloride is co-deposited with either water or HCl/water mixtures, infrared spectra indicative of solid D_2h-N₂O₄ are measured, as well as peaks corresponding to nitrate ions and cis-ClONO (chlorine nitrite). Reaction between ClNO2 and its isomer, cis-ClONO, is proposed as an explanation for the formation of dinitrogen tetraoxide in both systems. The proposed reaction mechanism for this hydrolysis is extended to the N₂O₅/H₂O/HCl deposits in order to explain the lack of observable ClNO₂ in such thin films.