Formation of Acetaldehyde in the Interstellar Medium from the Reaction of Methanol and Atomic Carbon in Interstellar Water Ice

Abstract

Acetaldehyde is a well-known interstellar molecule which is important for astrochemistry as it can undergo reaction with nitrogen-containing chemical species and can form amino acids or their precursors. Quantum chemical calculations at wB97XD/6-311++G(2d,p) level of theory were performed to study its formation mechanism from the reaction between atomic carbon C(3P) and methanol adsorbed on the surface of interstellar water ice. It was observed that acetaldehyde is formed from a two-step mechanism where the first step is a barrier-mediated step which generates radicals CH3 and H–CO followed by a barrierless addition of these radicals in interstellar ice (step 2). Due to a proton relay mechanism, the entrance barrier is very small and the formation of acetaldehyde is observed to be very efficient in the interstellar ice.