Combined experimental and computational study of the reactivity of the methanimine radical cation (H 2 CNH˙ + ) and its isomer aminomethylene (HCNH 2 ˙ + ) with propene (CH 3 CHCH 2 ).

The gas phase reactivity of the radical cation isomers H 2 CNH˙ + (methanimine) and HCNH 2 ˙ + (aminomethylene) with propene (CH 3 CHCH 2 ) has been investigated by measuring absolute reactive cross sections and product branching ratios, under single collision conditions, as a function of collision energy (in the range ∼0.07-11.80 eV) using guided ion beam mass spectrometry coupled with VUV photoionization for selective isomer generation. Experimental results have been merged with theoretical calculations to elucidate reaction pathways and structures of products. The H 2 CNH˙ + isomer is over a factor two more reactive than HCNH 2 ˙ + . A major channel from both isomers is production of protonated methanimine CH 2 NH 2 + via hydrogen-atom transfer reaction but, while H 2 CNH˙ + additionally gives charge and proton transfer products, the HCNH 2 ˙ + isomer leads instead to protonated vinylimine CH 2 CHCHNH 2 + , produced alongside CH 3 ˙ radicals. The reactions have astrochemical implications in the build up of chemical complexity in both the interstellar medium and the hydrocarbon-rich atmospheres of planets and satellites.