A chemical link between methylamine and methylene imine and implications for interstellar glycine formation.

Methylamine CH 3 NH 2 is considered to be an important precursor of interstellar amino acid because hydrogen abstraction might lead to the aminomethyl radical •CH 2 NH 2 that can react with •HOCO to form glycine, but direct evidence of the formation and spectral identification of •CH 2 NH 2 remains unreported. We performed the reaction H + CH 3 NH 2 in solid p-H 2 at 3.2 K and observed IR spectra of •CH 2 NH 2 and CH 2 NH upon irradiation and when the matrix was maintained in darkness. Previously unidentified IR spectrum of •CH 2 NH 2 clearly indicates that •CH 2 NH 2 can be formed from the reaction H + CH 3 NH 2 in dark interstellar clouds. The observed dual-cycle mechanism containing two consecutive H-abstraction and two H-addition steps chemically connects CH 3 NH 2 and CH 2 NH in interstellar media and explains their quasi-equilibrium. Experiments on CD 3 NH 2 produced CD 2 HNH 2 , in addition to •CD 2 NH 2 and CD 2 NH, confirming the occurrence of H addition to •CD 2 NH 2 .