Gas-phase preparation of carbonic acid and its monomethyl ester.
Gas-phase preparation of carbonic acid and its monomethyl ester.
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DOI：
10.1002/anie.201406969
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发表时间：
2014-10
影响因子：
--
通讯作者：
H. Reisenauer;J. Philipp Wagner;Peter R. Schreiner
中科院分区：
文献类型：
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作者：
H. Reisenauer;J. Philipp Wagner;Peter R. Schreiner
碳酸（H2 CO 3），生命的基本分子（例如，作为碳酸氢盐缓冲液），在溶液和固态中已经得到很好的表征，但是由于缺乏方便的制备方法，很长一段时间以来，它一直无法在气相中进行光谱表征;微波光谱只是最近才被记录下来。本文提出了一种新的和通用的方法，用于通过气相热解碳酸二叔丁酯和碳酸叔丁酯甲酯分别制备H2 CO 3及其单甲酯（CH 3 OCO 2 H）。H2 CO 3和CH 3 OCO 2 H在8 K下被捕获在惰性气体基质中，它们的红外光谱与高水平理论计算的结果[CCSD（T）/cc-pVQZ以外的焦点分析]非常吻合。尽管光谱也与H2 CO 3的β-多晶型物上方的气相的光谱完全一致，但对于先前报道的α-多晶型物，这不是真的。相反，α-H2 CO 3上方的气相对应于CH 3 OCO 2 H，这为过去几十年来对分子H2 CO 3进行的研究提供了新的线索。
Carbonic acid (H2CO3), an essential molecule of life (e.g., as bicarbonate buffer), has been well characterized in solution and in the solid state, but for a long time, it has eluded its spectral characterization in the gas phase owing to a lack of convenient preparation methods; microwave spectra were recorded only recently. Here we present a novel and general method for the preparation of H2CO3 and its monomethyl ester (CH3OCO2H) through the gas-phase pyrolysis of di-tert-butyl and tert-butyl methyl carbonate, respectively. H2CO3 and CH3OCO2H were trapped in noble-gas matrices at 8 K, and their infrared spectra match those computed at high levels of theory [focal point analysis beyond CCSD(T)/cc-pVQZ] very well. Whereas the spectra also perfectly agree with those of the vapor phase above the β-polymorph of H2CO3, this is not true for the previously reported α-polymorph. Instead, the vapor phase above α-H2CO3 corresponds to CH3OCO2H, which sheds new light on the research that has been conducted on molecular H2CO3 over the last decades.