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).