W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA.
Phys Chem Chem Phys. 2019 Jan 23;21(4):1952-1962. doi: 10.1039/c8cp06002a.
Methylamine (CH3NH2) and methanimine (CH2NH) represent essential building blocks in the formation of amino acids in interstellar and cometary ices. In our study, by exploiting isomer selective detection of the reaction products via photoionization coupled with reflectron time of flight mass spectrometry (Re-TOF-MS), we elucidate the formation of methanimine and ethylenediamine (NH2CH2CH2NH2) in methylamine ices exposed to energetic electrons as a proxy for secondary electrons generated by energetic cosmic rays penetrating interstellar and cometary ices. Interestingly, the two products methanimine and ethylenediamine are isoelectronic to formaldehyde (H2CO) and ethylene glycol (HOCH2CH2OH), respectively. Their formation has been confirmed in interstellar ice analogs consisting of methanol (CH3OH) which is ioselectronic to methylamine. Both oxygen-bearing species formed in methanol have been detected in the interstellar medium (ISM), while for methanimine and ethylenediamine only methanimine has been identified so far. In comparison with the methanol ice products and our experimental findings, we predict that ethylenediamine should be detectable in these astronomical sources, where methylamine and methanimine are present.
甲胺（CH3NH2）和甲亚胺（CH2NH）是星际和彗星冰中氨基酸形成的基本组成部分。在我们的研究中，通过利用光离子化结合反射飞行时间质谱（Re-TOF-MS）对反应产物进行异构体选择性检测，我们阐明了在高能电子（作为穿透星际和彗星冰的高能宇宙射线产生的次级电子的代理）暴露下，甲胺冰中形成甲亚胺和乙二胺（NH2CH2CH2NH2）的过程。有趣的是，这两个产物甲亚胺和乙二胺分别与甲醛（H2CO）和乙二醇（HOCH2CH2OH）等电子。它们的形成已在由甲醇（CH3OH）组成的星际冰类似物中得到证实，甲醇与甲胺等电子。含氧物种都已在星际介质（ISM）中检测到，而对于甲亚胺和乙二胺，目前仅鉴定出甲亚胺。与甲醇冰产物和我们的实验结果相比，我们预测在存在甲胺和甲亚胺的这些天文源中，应该可以检测到乙二胺。
