Theoretical study of amino acid precursor formation in the interstellar medium. 1. Reaction of methylenimine with hydrogen cyanide

Abstract

Search for amino acids and related compounds of prebiotic interest in the interstellar medium is one of the most challenging tasks for modern radio astronomy and astrobiology. Although no convincing detections of even the simplest amino acid glycine have been reported so far, rich organic chemistry of molecular clouds gives hope to expect even more complex species of prebiotic interest to be present in the interstellar medium. Methylenimine (HNCH 2), definitively detected in several Galactic objects, has been suggested as a possible precursor for glycine and its nitrile. One can imagine different reaction pathways, but most probable are those involving abundant, commonly found organic species. One of such species is hydrogen cyanide HCN. From common considerations, its interaction with methylenimine might produce glycine nitrile (H 2NCH 2CN). Here we present the results of ab initio quantum chemical study of this reaction, performed using the hybrid B3LYP functional and 6–31++G ∗∗ basis set. Three high energy transition states have been found, which make this reaction hardly feasible in the gas phase and suggest grain surface chemistry to be the only possible pathway for the glycine nitrile formation from methylenimine and HCN (if any).