Gas-Phase Reaction of NH2+ with Acetic Acid: Implications in Astrochemistry

A theoretical study of the ion-molecule reaction, NH2+ with acetic acid that could lead to precursors of glycine in the interstellar medium, has been carried out on the triplet and singlet potential energy surfaces. All stationary points and transition states on the (NO2C2H6)(+) triplet and singlet surfaces have been determined at the MP2(full) level with the cc-pVTZ basis set. Energetic data have been obtained at the CCSD(T) level employing the aug-cc-pVTZ basis set. The global minimum of the (NO2C2H6)(+) system is predicted to be protonated glycine in its singlet state, (1)A', and in general singlet states are more stable than the corresponding triplet ones. Formation of ionized glycine from this reaction is shown to be a feasible process under interstellar conditions, but the proton transfer channel and the formation of the compound CH2COOH+ seem to be more favorable processes on the triplet and singlet potential surfaces, respectively.