Acetic acid CH₃C(O)OH attracts significant attention in interstellar chemistry because it is considered to be a potential precursor for the formation of amino acids, such as glycine and alanine. The reaction NH₂ + •CH₂C(O)OH within the ice mantles and on an ice surface is considered to be responsible for the formation of glycine from CH₃C(O)OH. However, detailed experimental investigations are scarce. We took advantage of the unique properties of para-hydrogen (p-H₂), which serves as a quantum-solid matrix host and a medium for hydrogen-atom tunneling reactions, to investigate the reaction between CH₃C(O)OH and H atoms. On photolysis at 365 nm of a CH₃C(O)OH/Cl₂/p-H₂ matrix to produce Cl atoms and subsequent infrared irradiation to produce H atoms by promoting Cl + H₂ (v = 1) → H + HCl, new lines at 3581.6, 1681.0, 1455.6, 1350.7, 1180.9, 968.4, 898.4, 766.4, and 579.5 cm^–1 were observed and assigned to the carboxymethyl radical, •CH₂C(O)OH; the observed new spectrum agrees satisfactorily with IR intensities and scaled harmonic vibrational wavenumbers predicted with the B3LYP/aug-cc-pVTZ method. The observation of only •CH₂C(O)OH as a product of H + CH₃C(O)OH indicates that the reaction proceeds through H-abstraction at the CH₃ moiety, whereas H-abstraction from the OH-site and other H-addition channels are unfavorable. Further H-abstraction from •CH₂C(O)OH was unobserved. This previously neglected H-abstraction from CH₃C(O)OH is expected to be a major channel for the formation of •CH₂C(O)OH on a grain surface and bulk ice and to play an important role in the formation of glycine and other complex organic molecules (COM) in the interstellar media.

中文翻译：

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氢原子萃取乙酸制氢形成固体对氢中的羧甲基自由基•CH ₂ C（O）OH及其在天化学中的意义

乙酸CH ₃ C（O）OH在星际化学中备受关注，因为它被认为是形成氨基酸（例如甘氨酸和丙氨酸）的潜在前体。在冰套中和在冰表面上的NH ₂ +•CH ₂ C（O）OH反应被认为是由CH ₃ C（O）OH形成甘氨酸的原因。但是，缺乏详细的实验研究。我们利用对氢（p -H ₂）的独特性质来研究CH ₃之间的反应，该对氢用作量子固体基质主体和氢原子隧穿反应的介质C（O）OH和H原子。CH ₃ C（O）OH / Cl ₂ / p -H ₂基质在365 nm处光解产生Cl原子，然后通过促进Cl + H ₂（v = 1）→H + HCl进行红外辐射产生H原子，观察到了在3581.6、1681.0、1455.6、1350.7、1180.9、968.4、898.4、766.4和579.5 cm ^–1处的新行，并将其分配给羧甲基自由基•CH ₂ C（O）OH；观测到的新光谱与IR强度和B3LYP / aug-cc-pVTZ方法预测的缩放谐波振动波数令人满意地吻合。仅观察到作为H + CH ₃产物的•CH ₂ C（O）OHC（O）OH表示反应是通过在CH ₃部分进行H抽提进行的，而从OH-位和其他H加成通道的H抽提是不利的。未观察到从•CH ₂ C（O）OH进一步吸氢。CH ₃ C（O）OH的这种先前被忽略的H吸收有望成为在谷物表面和大块冰上形成•CH ₂ C（O）OH的主要通道，并在形成冰的过程中发挥重要作用。星际介质中的甘氨酸和其他复杂有机分子（COM）。