Reaction of atomic carbon with ammonia. The mechanism of formation of amino acid precursors

The formation of amino acid precursors in the reaction of atomic carbon with water and ammonia at 77 K

“…We have demonstrated that the reaction of atomic carbon with ammonia proceeds by the mechanism shown in Scheme 1 in which an initial complex between carbon and ammonia can either decompose to HNC and hydrogen or rearrange to aminomethylene, 1 [7]. Subsequent acid-base reaction of HNC with ammonia gives…”

“…The N-methylglycine probably results from the reaction of HCN with the small amount of N-methylmethanimine formed in the dehydrochlorination of Nchloromethylamine [12]. The table demonstrates that the ratio of GLY to ASP in this reaction is 1.38 while the reaction of carbon with ammonia and HCN gives a GLY:ASP ratio of 40 [7]. These facts lead us to conclude that reaction of carbon with 2 does indeed generate a species which can react with HCN to generate aspartic acid precursor, 7.…”

“…These facts lead us to conclude that reaction of carbon with 2 does indeed generate a species which can react with HCN to generate aspartic acid precursor, 7. Two possible routes to 7 are shown in Equations (6) and (7). In Equation (6), carbon is postulated to add to the C-N double bond in 2 to give an initial azacyclopropylidene, 8.…”

“…There is ample analogy for the initial steps of both Equations (6) and (7). Thus, addition of atomic carbon to C-C double bonds yields cyclopropylidenes and thence allenes [8] in analogy to the postulated formation of ketenimine in Equation (6).…”

“…It is easy to imagine the condensation of a gaseous carbon atom on a cold surface such as an interstellar grain, which has been coated with water and ammonia, leading to the same amino acid precursors that we observe in our reactions. We have speculated on the mechanism of the formation of these amino acid precursors [7] and in this paper we report the results of additional experiments which bear on these interesting reactions. …”