Carbamate Formation in the System (2-Methylpiperidine + Carbon Dioxide) by Raman Spectroscopy and X-ray Diffraction,The Journal of Physical Chemistry B

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Carbamate Formation in the System (2-Methylpiperidine + Carbon Dioxide) by Raman Spectroscopy and X-ray Diffraction
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2018-11-21 , DOI: 10.1021/acs.jpcb.8b08253
O. Fandino ₁ , S. Sasidharanpillai ₁ , D. V. Soldatov ₁ , P. R. Tremaine ₁

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In aqueous solution, 2-methylpiperine (2-MP) has been proposed as a phase-separating amine for carbon-capture applications, whose carbamate is considered to be unstable due to steric hindrance. This paper demonstrates, for the first time, that the carbamate can be synthesized as the salt of the 2-methylpiperidinium cation (2-MPH⁺) and the 2-methylpiperidine-N-carboxylate anion (2-MPCOO^–) by adding carbon dioxide gas to anhydrous liquid 2-MP at CO₂/amine ratios α > 0.32 to yield well-defined prismatic crystals. Raman spectra have been measured for anhydrous liquid 2-MP and aqueous solutions of 2-MP and 2-MPH⁺Cl^– at 298 K. The spectra of anhydrous liquid 2-MP, containing dissolved CO₂ at lower CO₂/amine ratios,_. clearly showed the presence of 2-MPH⁺ and several unidentified bands that were attributed to the carbamate, 2-MPCOO^–. Quantum chemical calculations at the B3LYP/6-311++G(d,p) level of theory yielded simulated Raman spectra consistent with the experimental spectra. The spectra show the methyl group of both liquid and aqueous 2-MP and that of aqueous 2-MPH⁺Cl^– to be in the equatorial position. The crystal structure shows the same conformations in the solid state and confirms that Raman spectroscopy can be used to determine the conformation of 2-MP species in the liquid state and aqueous solutions.

中文翻译：

通过拉曼光谱和X射线衍射在系统（2-甲基哌啶+二氧化碳）中形成氨基甲酸酯

在水溶液中，已经提出了2-甲基哌啶（2-MP）作为用于碳捕获应用的相分离胺，其氨基甲酸酯由于空间位阻而被认为是不稳定的。本文首次证明，可通过添加二氧化碳将氨基甲酸酯合成为2-甲基哌啶鎓阳离子（2-MPH ⁺）和2-甲基哌啶-N-羧酸根阴离子（2-MPCOO ^–）的盐^。气体转化为无水液体2-MP，CO ₂ /胺比α> 0.32，得到明确的棱柱晶体。已在298 K下测量了无水液体2-MP以及2-MP和2-MPH ⁺ Cl ^–的水溶液的拉曼光谱。包含溶解的CO的无水液体2-MP的光谱₂在较低的CO ₂ /胺比率_。清楚地表明2-MPH存在⁺和几个不明身份的乐队是归因于氨基甲酸酯，2- MPCOO ^-。在理论的B3LYP / 6-311 ++ G（d，p）水平进行量子化学计算，得出与实验光谱一致的模拟拉曼光谱。该光谱显示出液体和含水2-MP的甲基和水2-MPH的⁺氯^-是在赤道位置。晶体结构在固态下显示相同的构型，并证实拉曼光谱法可用于确定液态和水溶液中的2-MP物质的构型。

更新日期：2018-11-24

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