Adams’s catalyst, also known as platinum oxide, is usually represented as platinum(IV) oxide hydrate, PtO2•H2O. It is a catalyst for hydrogenationand hydrogenolysis in organic synthesis. This dark brown powder is commercially available. The oxide itself is not an active catalyst, but it becomes active after exposure to hydrogen whereupon it converts to platinum black, which is responsible for reactions.

Adams’s catalyst is used for many applications. It has shown to be valuable for hydrogenation and hydrogenolysis, dehydrogenation, and oxidation reactions. During the reaction, platinum metal (platinum black) is formed which has been cited to be the active catalyst.[3][4]Hydrogenation occurs with syn stereochemstry when used on an alkyne resulting in a cis-alkene. Some of the most important transformations include the hydrogenation of nitro compounds to amines and ketones to alcohols. Although, reductions of alkenes can be performed with Adam’s catalyst in the presence of nitro groups without reducing the nitro group. When reducing nitro compounds to amines, platinum catalysts are preferred over palladium catalysts to minimize hydrogenolysis. The catalyst is also used for the hydrogenolysis of phenyl phosphate esters, a reaction that does not occur with palladium catalysts. The pH of the solvent significantly affects the reaction course, and reactions of the catalyst are often enhanced by conducting the reduction in neat acetic acid, or solutions of acetic acid in other solvents.

二氧化铂也称亚当斯催化剂氧化铂,通常以一水合物的形式存在,是有机合成中氢化和氢解反应的催化剂,深褐色[粉末。加热超过650℃时分解为金属铂和氧气。二氧化铂自身无催化活性,但遇氢气后,可转变为有催化活性的铂黑

发展过程

发展二氧化铂前,有机物加氢常用胶体钯、胶体铂或铂黑作催化剂。胶体催化剂虽活性较强,但反应后很难与产物分离。这导致很多反应都是用铂黑催化进行,促使研究者改良铂黑的制备的方法。对此,亚当斯曾说:

我让学生去做催化还原,我们先是用铂黑催化剂,利用当时认为是最好的方法来制备,但铂黑的催化效果实在不好——同样方法制得的催化剂,有时有催化活性,有时就没有活性。于是我就开始研究活性铂黑更好的制备方法(从而导致了二氧化铂的发现)。[4]

安全

二氧化铂自身基本无害,但它被氢气还原后形成的铂黑可自燃。反应中应保持铂黑润湿,避免与氧气接触。


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