Photochemical dehydration of acetamide in a cryogenic matrix

Abstract

Vacuum ultraviolet (VUV) irradiation of acetamide has been monitored by Fourier transform infrared spectroscopy in argon matrix at 10 K. Several primary photoproducts, including HNCO ∶ CH₄ and CO ∶ CH₃NH₂ molecular complexes, and acetimidic acid, which is reported for the first time, were characterized. The acetimidic acid identification was based on comparison between the experimental and theoretical (B3LYP) infrared spectra. Acetimidic acid is found in argon matrix in the (s-Z)–(E) and (s-Z)–(Z) configurations. It is also an intermediate in the VUV decomposition process, its dehydration leads to the formation of CH₃CN ∶ H₂O molecular complex. The assignment of the complex was achieved by co-depositing the pairs of respective species and by ab initio calculation.