2019MNRAS.485.5210K

Possible formation routes of interstellar amino acids have been proposed where the first step consists in the transformation of organic nitriles (RCH₂ - C≡N) into ketenimines (RCH = C = NH). Such a transformation shows high-energy barriers and needs energetic processing to occur. We show in this study that the CN bond could be activated through H-addition reactions to form ketenimines when starting from organic α, β-unsaturated nitriles (C≡N). Consequently, both methyl ketenimine CH₃CH = C = NH and ethylcyanide CH₃CH₂C≡N might have their origin from H₂C = CH - C≡N + 2H reaction occurring on the interstellar icy grains. During the hydrogenation of H₂C = CH - C≡N ice under interstellar conditions, CH₃CH₂C≡N has been formed with an abundance 10 times higher than that of CH₃CH = C = NH. Our measurements lead us to conclude that such a distribution would be directly linked to the π-electrons delocalization H₃C - C°H - C≡N - H₃C - CH = C = N° occurring during the reduction of the CC double bond of acrylonitrile.