A quantum chemical study of the formation of cyanide (CN−) and acetate (CH3COO-) ions in astrophysical ices via proton transfer from HCN, HNC, or CH3COOH to NH3

Quantum chemical calculations at the B3LYP/6-31+G∗∗ and MP2/6-31+G∗∗ levels were employed to characterize proton transfer from hydrogen cyanide (HCN), hydrogen isocyanide (HNC), and acetic acid (CH3COOH) to ammonia (NH3) in clusters with up to 14 H2O molecules in order to model behavior in amorphous icy grain mantles. In keeping with previous work on cyanic acid (HOCN), isocyanic acid (HNCO), and formic acid (HCOOH), the calculations found that a proton transfers from the acids to NH3 with no barrier in clusters of sufficient size to form solvated anion complexes with NH4+. The infrared band origins and intensities for characteristic vibrational motions of the acetate and cyanide anions are identified in order to provide guidance for experimental studies and astronomical observations.