The reactivity of methanimine radical cation (H2CNH•+) and its isomer aminomethylene (HCNH2•+) with methane

Experimental and theoretical studies are presented on the reactions of the isomeric radical cations H2CNH•+ and HCNH2•+ with CH4. Ionic isomers were generated selectively by VUV dissociative photoionization of azetidine and cyclopropylamine precursors respectively. Both exclusively give H2CNH2+ plus CH3• as products, but differences are observed related to a competition between stripping and complex-mediated H-transfer. Astrochemical implications for Titan’s atmosphere are briefly discussed, where the presence of methanimine (H2CNH), a key prebiotic molecule and a potential precursor for tholins, is proposed on the basis of atmospheric models and the observation of CH2NH2+ ions in Cassini mass spectrometric data.