Views: 3 Author: Site Editor Publish Time: 2022-05-09 Origin: Site
Sodium borohydride is an inorganic compound with the chemical formula NaBH4. It is a white to grayish white crystalline powder with strong moisture absorption. Its alkaline solution is brownish yellow. It is one of the most commonly used reducing agents. Soluble in water, liquid ammonia and amines, easily soluble in methanol, slightly soluble in ethanol and tetrahydrofuran, insoluble in ether, benzene and hydrocarbons. It is stable in dry air, decomposes in wet air, and also decomposes under heating at 500 ℃. Generally, sodium borohydride cannot reduce esters, amides, carboxylic acids and nitriles, but when the carbonyl group of esters α With the exception of the presence of heteroatoms at the position, the ester can be reduced. It is usually used as reducing agent for aldehydes, ketones and acyl chloride, foaming agent for plastic industry, paper bleaching agent, and hydrogenation agent for manufacturing dihydrostreptomycin in pharmaceutical industry.
It is listed in the list of dangerous chemicals prone to explosion and controlled in accordance with the measures for the administration of public security of dangerous chemicals prone to explosion.
Sodium borohydride was discovered by H. C. brown and his mentor Schlesinger at the University of Chicago in 1942. At first, in order to study the properties of borane and carbon monoxide complex, it was unexpectedly found that borane has the ability to reduce organic carbonyl compounds. Borane was a rare substance at that time, so it did not attract the attention of organic chemists. The development of borane chemistry benefited from the Second World War, when the U.S. Department of defense needed to find a volatile uranium compound with the lowest molecular weight for the enrichment of fissile material uranium 235. Uranium borohydride U (BH4) 4 meets this requirement. The synthesis of this compound requires lithium hydride, but there is little supply of lithium hydride, so cheap sodium hydride is used as raw material, and sodium borohydride is found in this process. Later, because the problem of uranium hexafluoride treatment process was solved, the U.S. Department of defense abandoned the plan to enrich uranium 235 through uranium borohydride, and Brown's research topic became how to easily prepare sodium borohydride. Army Signal Corps is interested in the use of this new compound to produce large amounts of hydrogen. With their support, they carried out relevant research. Pure sodium borohydride was obtained by recrystallization with ether solvents.
Sodium borohydride has α、β、γ Three crystal forms. At room temperature α Type NaCl structure cubic crystal; 6.3gpa to β Tetragonal crystal, converted to at 8.9GPa γ Type orthogonal crystal.