On the Formation of the Popcorn Flavorant 2,3‐Butanedione (CH 3 COCOCH 3 ) in Acetaldehyde‐Containing Interstellar Ices
On the Formation of the Popcorn Flavorant 2,3‐Butanedione (CH 3 COCOCH 3 ) in Acetaldehyde‐Containing Interstellar Ices
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爆米花香料2,3丁二酮(CH 3 COCOCH 3 )在乙醛星际冰中的形成
DOI：
10.1002/cphc.202000116
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发表时间：
2020
期刊：
影响因子：
2.9
通讯作者：
Kaiser, Ralf I.
中科院分区：
文献类型：
--
作者：
Kleimeier, N. Fabian;Turner, Andrew M.;Fortenberry, Ryan C.;Kaiser, Ralf I.
乙醛(CH3CHO)在整个星际介质中普遍存在，并在冷分子云、恒星形成区域和陨石(如Murchison)中被观察到。乙醛是最简单的含甲基醛，通过Strecker合成，是合成糖、脱氧核糖和氨基酸等益生菌分子的关键前体。在这项研究中，我们首次在实验室检测到2，3-丁二酮(双乙酰，CH3COCH3)-一种黄油和爆米花香料-在乙醛星际模拟冰中合成，暴露在5 K的电离辐射下。详细的同位素替代实验结合升华分子的可调真空紫外光电离表明，2，3-丁二酮主要是通过两个乙酰基(CH3ĊO)的无障碍自由基-自由基反应生成的。这些过程对于详细了解复杂的有机分子是如何在深空合成的，从而通过一个强有力的星系宇宙射线驱动的非平衡化学来约束在含有乙醛的地外冰层中形成的分子的分子结构和复杂性是至关重要的。
Acetaldehyde (CH3CHO) is ubiquitous throughout the interstellar medium and has been observed in cold molecular clouds, star forming regions, and in meteorites such as Murchison. As the simplest methyl‐bearing aldehyde, acetaldehyde constitutes a critical precursor to prebiotic molecules such as the sugar deoxyribose and amino acids via the Strecker synthesis. In this study, we reveal the first laboratory detection of 2,3‐butanedione (diacetyl, CH3COCOCH3) – a butter and popcorn flavorant – synthesized within acetaldehyde‐based interstellar analog ices exposed to ionizing radiation at 5 K. Detailed isotopic substitution experiments combined with tunable vacuum ultraviolet (VUV) photoionization of the subliming molecules demonstrate that 2,3‐butanedione is formed predominantly via the barrier‐less radical–radical reaction of two acetyl radicals (CH3ĊO). These processes are of fundamental importance for a detailed understanding of how complex organic molecules (COMs) are synthesized in deep space thus constraining the molecular structures and complexity of molecules forming in extraterrestrial ices containing acetaldehyde through a vigorous galactic cosmic ray driven non‐equilibrium chemistry.