Electrocatalytic Hydrogenation of Oxygenated Compounds in Aqueous Phase,Organic Process Research & Development

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Electrocatalytic Hydrogenation of Oxygenated Compounds in Aqueous Phase
Organic Process Research & Development ( IF 3.1 ) Pub Date : 2018-09-24 00:00:00 , DOI: 10.1021/acs.oprd.8b00236
Udishnu Sanyal ₁ , Juan Lopez-Ruiz ₁ , Asanga B. Padmaperuma ₁ , Jamie Holladay ₁ , Oliver Y. Gutiérrez ₁

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Electrocatalytic hydrogenation is a strategy to hydrogenate biogenic compounds under ambient conditions by replacing the thermal and H₂ inputs by cathodic potential. This work compares the performances of this approach (in aqueous phase at room temperature) for the conversion of a variety of model oxygenated compounds over a series of metals. The target functionalities were carbonyl groups, aromatic rings, and ether bonds. All of the metals explored (Pt, Rh, Pd, and Cu) are active for the reduction of carbonyl compounds to alcohols. The conversion rate of benzaldehyde increased as a function of the metal as Pt < Rh < Pd (Cu was tested under different conditions). In contrast, only Rh and Pt were active for hydrogenation of aromatic rings (Rh was more active than Pt). In a comparison of the target functionalities, carbonyl groups are more reactive than aromatic rings and ether bonds in phenolic compounds and diaryl ethers on all of the explored metals. This carbonyl reactivity, however, is enhanced by the aromaticity of the molecule. Hence, the reactivity trend of the examined molecules is butyraldehyde < furfural < acetophenone < benzaldehyde. For phenolic compounds, phenol is more reactive than cresol and methoxyphenol. Thus, the presence of substituent groups on the functionality being converted (either carbonyl or aromatic ring) decreases the conversion rate. Ether bonds are cleaved under electrocatalytic conditions, which opens two main pathways for the conversion of aryl ethers: hydrogenation of the aromatic ring and hydrogenolysis of the ether bonds, whereas hydrolysis occurs as a minor pathway. Electrocatalytic hydrogenation competes with the H₂ evolution reaction under the conditions of the tests, and therefore, the Faradaic efficiency (the fraction of current utilized in hydrogenation) and hydrogenation rate are correlated. That is, within the potential range explored, increasing hydrogenation rates lead to higher Faradaic efficiencies. The slope of this correlation, however, depends on the potential and on the functionality being hydrogenated.

中文翻译：

含氧化合物在水相中的电催化加氢

电催化氢化是一种在环境条件下通过替代热和H ₂来氢化生物化合物的策略。阴极电位输入。这项工作比较了此方法（在室温下在水相中）在一系列金属上将各种模型含氧化合物转化的性能。目标官能度为羰基，芳环和醚键。所探索的所有金属（Pt，Rh，Pd和Cu）均具有将羰基化合物还原为醇的活性。苯甲醛的转化率随着金属的增加而增加，Pt <Rh <Pd（在不同条件下测试了Cu）。相反，只有Rh和Pt对芳香环的氢化具有活性（Rh比Pt更具活性）。在与目标官能团的比较中，羰基的反应性比所有勘探金属上的酚类化合物和二芳基醚中的芳环和醚键更高。然而，该羰基反应性通过分子的芳香性增强。因此，所检查分子的反应趋势为丁醛<糠醛<苯乙酮<苯甲醛。对于酚类化合物，苯酚比甲酚和甲氧基苯酚更具反应性。因此，在被转化的官能团（羰基或芳族环）上取代基的存在降低了转化率。醚键在电催化条件下裂解，这为芳基醚的转化打开了两个主要途径：芳环的氢化和醚键的氢解，而水解则是次要途径。电催化加氢与氢竞争糠醛<苯乙酮<苯甲醛。对于酚类化合物，苯酚比甲酚和甲氧基苯酚更具反应性。因此，在被转化的官能团（羰基或芳族环）上取代基的存在降低了转化率。醚键在电催化条件下裂解，这为芳基醚的转化打开了两个主要途径：芳环的氢化和醚键的氢解，而水解则是次要途径。电催化加氢与氢竞争糠醛<苯乙酮<苯甲醛对于酚类化合物，苯酚比甲酚和甲氧基苯酚更具反应性。因此，在被转化的官能团（羰基或芳族环）上取代基的存在降低了转化率。醚键在电催化条件下裂解，这为芳基醚的转化打开了两个主要途径：芳环的氢化和醚键的氢解，而水解则是次要途径。电催化加氢与氢竞争醚键在电催化条件下裂解，这为芳基醚的转化打开了两个主要途径：芳环的氢化和醚键的氢解，而水解则是次要途径。电催化加氢与氢竞争醚键在电催化条件下裂解，这为芳基醚的转化打开了两个主要途径：芳环的氢化和醚键的氢解，而水解则作为次要途径发生。电催化加氢与氢竞争在试验条件下发生₂放出反应，因此，法拉第效率（氢化中使用的电流的比例）和氢化速率相关。也就是说，在所探索的潜力范围内，增加的氢化速率会导致更高的法拉第效率。然而，这种相关性的斜率取决于电势和被氢化的官能度。

更新日期：2018-09-24

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