Department of Chemistry, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark.
Chemistry. 2018 Dec 3;24(67):17832-17837. doi: 10.1002/chem.201804402. Epub 2018 Nov 7.
Zinc oxide has been developed as a catalyst for the dehydrogenation of primary alcohols into carboxylic acids and hydrogen gas. The reaction is performed in mesitylene solution in the presence of potassium hydroxide, followed by workup with hydrochloric acid. The transformation can be applied to both benzylic and aliphatic primary alcohols and the catalytically active species was shown to be a homogeneous compound by a hot filtration test. Dialkylzinc and strongly basic zinc salts also catalyze the dehydrogenation with similar results. The mechanism is believed to involve the formation of a zinc alkoxide which degrades into the aldehyde and a zinc hydride. The latter reacts with the alcohol to form hydrogen gas and regenerate the zinc alkoxide. The degradation of a zinc alkoxide into the aldehyde upon heating was confirmed experimentally. The aldehyde can then undergo a Cannizzaro reaction or a Tishchenko reaction, which in the presence of hydroxide leads to the carboxylic acid.
氧化锌已被开发为一种催化剂，用于伯醇脱氢为羧酸和氢气。反应在均三甲苯溶液中进行，存在氢氧化钾，然后用盐酸进行后处理。该转化可应用于苄基和脂肪族伯醇，并且通过热过滤测试表明催化活性物质是均相化合物。二烷基锌和强碱锌盐也以类似的结果催化脱氢。该机理被认为涉及锌醇盐的形成，其降解为醛和锌氢化物。后者与醇反应生成氢气并再生锌醇盐。通过实验证实，在加热时，锌醇盐降解为醛。然后，醛可以进行康尼扎罗反应或蒂希琴科反应，在存在氢氧根的情况下，这会导致羧酸的形成。
