Butscher Teddy, Duvernay Fabrice, Rimola Albert, Segado-Centellas Mireia, Chiavassa Thierry
Aix-Marseille Université, Laboratoire PIIM, Team ASTRO, Service 252, Saint Jérôme, Ave. Escadrille Normandie Niemen, 13013 Marseille, France.
Departament de Quimica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Spain.
Phys Chem Chem Phys. 2017 Jan 25;19(4):2857-2866. doi: 10.1039/c6cp07024h.
Many complex organic molecules (hereafter COMs) have been detected in different regions of the interstellar medium (ISM). In each region, different energetic processes - UV irradiation, atom bombardments, etc. - that could be linked to the formation of detected COMs may occur depending on the environment. Several formation mechanisms were proposed but increasing attention is paid to radical recombination reactions. Previous studies showed that glycolaldehyde (HC(O)CHOH) and ethylene glycol (HOCHCHOH) are formed by radical recombination between HC˙O and ˙CHOH, and by ˙CHOH dimerisation, respectively. Formyl (HC˙O), one of the most famous astrophysically-relevant radical species, has been detected as a gaseous component of the ISM. Its reactivity was already attributed to the formation of several COMs. This work aims to study the dimerisation of formyl radical HC˙O using a cryogenic matrix technique. The evolution of the chemical sample composition is monitored by infrared spectroscopy and by mass spectrometry during temperature programmed desorption (TPD) monitoring. Results indicate that the reaction of one HC˙O with another does not lead to the direct formation of glyoxal (HC(O)C(O)H) but yields HCO and CO. Results are also compared with those for the reaction between two ˙CHOH radicals and the recombination between HC˙O and ˙CHOH. Also, glyceraldehyde was tentatively detected in our experiment using different spectroscopic techniques. A radical mechanism is proposed to explain its formation in our experiments. Complementary quantum chemical calculations provide an atomistic interpretation of the experimental findings.
在星际介质（ISM）的不同区域已检测到许多复杂有机分子（以下简称COM）。在每个区域，根据环境的不同，可能会发生与检测到的COM形成相关的不同能量过程，如紫外线照射、原子轰击等。人们提出了几种形成机制，但自由基复合反应越来越受到关注。先前的研究表明，乙醇醛（HC(O)CHOH）和乙二醇（HOCHCHOH）分别是由HC˙O和˙CHOH之间的自由基复合以及˙CHOH二聚化形成的。甲酰基（HC˙O）是最著名的与天体物理相关的自由基物种之一，已被检测为ISM的气态成分。其反应活性已被认为与几种COM的形成有关。这项工作旨在使用低温基质技术研究甲酰基自由基HC˙O的二聚化。在程序升温脱附（TPD）监测过程中，通过红外光谱和质谱监测化学样品组成的演变。结果表明，一个HC˙O与另一个HC˙O的反应不会直接导致乙二醛（HC(O)C(O)H）的形成，而是生成HCO和CO。还将结果与两个˙CHOH自由基之间的反应以及HC˙O和˙CHOH之间的复合反应结果进行了比较。此外，在我们的实验中使用不同的光谱技术初步检测到了甘油醛。提出了一种自由基机制来解释其在我们实验中的形成。补充的量子化学计算为实验结果提供了原子层面的解释。
