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Infrared Spectroscopy of the Astrochemically Relevant Protonated Formaldehyde Dimer
The Journal of Physical Chemistry A ( IF 2.9 ) Pub Date : 2017-12-28 00:00:00 , DOI: 10.1021/acs.jpca.7b10573
J. Philipp Wagner 1 , David C. McDonald 1 , Michael A. Duncan 1
Affiliation  

The protonated formaldehyde dimer (H2CO)2H+ was generated in an electrical discharge and supersonic expansion of argon saturated with formalin solution vapor. Its infrared spectrum was measured in the region from 900 to 4000 cm–1 employing infrared laser photodissociation and messenger atom tagging. Comparison of the experiment to quantum chemical computations at the CCSD(T)/cc-pVQZ//MP2/cc-pVTZ level reveals that the experimentally observed structure is the head-to-tail dimer and not the more stable proton-bound dimer. This is consistent with the usually observed C–O bond formation upon formaldehyde oligomerization under acidic conditions in solution and resembles the structure of the neutral (H2CO)2 dimer in the gas phase. There is no evidence for the formation of other isomers, most notably protonated glycolaldehyde, that could result from covalent bond formation. These findings may be relevant to a proposed carbohydrate formation mechanism in the interstellar medium starting from protonated formaldehyde dimer.

中文翻译:

与天体化学相关的质子化甲醛二聚体的红外光谱

质子化的甲醛二聚体(H 2 CO)2 H +是在充满福尔马林溶液蒸气的氩气的放电和超音速膨胀中产生的。通过红外激光光解和信使原子标记,在900至4000 cm –1范围内测量了其红外光谱。实验与CCSD(T)/ cc-pVQZ // MP2 / cc-pVTZ级别的量子化学计算的比较表明,实验观察到的结构是头尾二聚体,而不是更稳定的质子结合二聚体。这与在酸性条件下溶液中甲醛低聚时通常观察到的C–O键形成是一致的,并且类似于中性(H 2 CO)的结构。2在气相二聚体。没有证据表明可能由共价键形成导致形成其他异构体,尤其是质子化的乙醇醛。这些发现可能与从质子化甲醛二聚体开始的星际介质中拟议的碳水化合物形成机制有关。
更新日期:2017-12-28
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