Mechanisms of interstellar synthesis of glycine, alanine, and serine from aminonitriles, OH, and H₂O

A new potential energy surface for forming glycine in the gas phase, starting from association of aminoacetonitrile (NH₂CH₂CN) with OH followed by subsequent hydrolysis, was determined using CBS-QB3 calculation. The overall activation energy was 90 kJ mol⁻¹ or 0 without or with catalytic H₂O, respectively. Alanine or serine was formed from 2-aminopropionitrile (CH₃CH(NH₂)CN) or 2-amino-3-hydrxypropionitrile (HOCH₂CH(NH₂)CN) instead of aminoacetonitrile with the overall activation energies of 89 or 49 kJ mol⁻¹, respectively. When an additional H₂O was involved in each reaction as a catalyst, barrierless reaction pathways were obtained. These results suggest that it is possible for investigated reactions to occur in interstellar ices along the proposed pathways, taking kinetic aspects into account.