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Sodium borohydride is an inorganic substance with a chemical formula of NaBH4. It is white to off-white fine crystalline powder or lumps. It has strong hygroscopicity. 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 humid air, and also decomposes under heating at 400°C. Under normal circumstances, sodium borohydride cannot reduce esters, amides, carboxylic acids and nitriles, except when there are heteroatoms in the α-position of the carbonyl group of the ester, the ester can be reduced.
Sore throat, cough, shortness of breath, headache, abdominal pain, diarrhea, dizziness, conjunctival hyperemia, pain and other symptoms after contact with sodium borohydride. Inhalation or skin contact with the reagent is harmful to humans. This reagent is generally used as a reducing agent for aldehydes, ketones, and acid chlorides, as a foaming agent in the plastics industry, a bleaching agent for papermaking, and a hydrogenating agent for the manufacture of dihydrostreptomycin in the pharmaceutical industry. Sodium borohydride should be kept dry, and should be handled carefully in a fume hood. It should be stored in a cool, dry warehouse, away from heat, fire and flammable materials, and do not store or transport it with inorganic acids.
Physical properties：White crystalline powder, strong hygroscopicity, easy to deliquesce by absorbing water. Soluble in water, liquid ammonia and amines. Easily soluble in methanol, slightly soluble in ethanol and tetrahydrofuran. Insoluble in ether, benzene, hydrocarbons. It is stable in dry air, decomposes in moist air, and also decomposes when heated to 400°C.
1. Since the hydrogen in sodium borohydride has a partial negative charge (the electronegativity of B is smaller than that of H), the hydrogen in alcohols and amines -OH, -NH-, and -NH2 have more partial positive charges. Electric charge, so the BH4- in sodium borohydride can form a double hydrogen bond with the molecules that make up these substances, so sodium borohydride can be dissolved in water, liquid ammonia, alcohols and amines.
2. Sodium borohydride will react slowly with water and alcohol and other substances containing hydroxyl groups to release hydrogen (the equation is as follows). At the same time, because the reaction is slow, the loss of sodium borohydride in a short period of time is small, so sodium borohydride Alkaline solutions, methanol, ethanol can be used as solvents.
3. Sodium borohydride is an inorganic compound with strong selective reduction. It is commonly used as a reducing agent in inorganic synthesis and organic synthesis  with good chemical selectivity. It can achieve the reduction of aldehydes and ketones carbonyl under very mild conditions to generate primary alcohols and secondary alcohols. A small amount of sodium borohydride can reduce the nitrile to an aldehyde, and an excess can reduce it to an amine. It can selectively reduce carbonyl and aldehyde groups to hydroxyl groups, and can also reduce carboxyl groups to aldehyde groups without interacting with esters and amides, and generally does not react with carbon-carbon double bonds and triple bonds: