inorganic compound
Popular Science China | This entry is reviewed by the entry writing and application project of Popular Science China.
Review expert Bao Xu Shen
Sodium borohydride is an inorganic compound with chemical formula of NaBH4, which is white to grayish white crystalline powder with strong hygroscopicity, and its alkaline solution is brownish yellow, so it is one of the most commonly used reducing agents. Soluble in water, liquid ammonia and amines, soluble in methanol, slightly soluble in ethanol and tetrahydrofuran, insoluble in ether, benzene and hydrocarbons. Stable in dry air, decomposed in humid air, and also decomposed when heated at 500℃. Under normal circumstances, sodium borohydride can't reduce esters, amides, carboxylic acids and nitriles, and the esters can be reduced unless there are heteroatoms in the α position of the carbonyl group of the esters. It is usually used as reducing agent for aldehydes, ketones and acyl chlorides, foaming agent for plastics industry, bleaching agent for papermaking, and hydrogenation agent for manufacturing dihydrostreptomycin in pharmaceutical industry.
It is listed in the List of Explosive Hazardous Chemicals [8] and managed according to the Measures for Public Security Management of Explosive Hazardous Chemicals [9].
Chinese name
sodium borohydride
Foreign name
sodium borohydride
Another name
Sodium tetrahydroborate
chemical formula
sodium borohydride
molecular weight
37.83[2]
Related video
00:54
Preparation of catalyst by sodium borohydride reduction method
37,000 broadcasts
Study the brief history of molecular structure, physical and chemical properties, and the safety information of emergency treatment of related hazards in the application field of computational chemistry data, ta said.
A brief history of research
Sodium borohydride was discovered by H C· Brown and his mentor Schlesinger in 1942 at the University of Chicago. Firstly, in order to study the properties of borane and carbon monoxide complexes, it was unexpectedly found that borane has the ability to reduce organic carbonyl compounds. Because borane was a rare substance at that time, it did not attract the attention of organic chemists. The development of borane chemistry benefited from World War II, when the U.S. Department of Defense needed to find a volatile uranium compound with the smallest molecular weight to concentrate the fissile material uranium -235. Uranium borohydride U(BH4)4 meets this requirement. The synthesis of this compound needs lithium hydride, but the supply of lithium hydride is very small, so cheap sodium hydride is used as raw material, and sodium borohydride is found in this process. Later, because the treatment process of uranium hexafluoride was solved, the US Department of Defense gave up the plan of enriching uranium 235 through uranium borohydride, and Brown's research topic became how to prepare sodium borohydride conveniently. The Army Signal Corps is interested in using this new compound to produce a large amount of hydrogen. With their support, relevant industrialization research was carried out. Recrystallizing with ether solvent to obtain pure sodium borohydride. [3]
Sodium borohydride: 3D structural formula
molecular structure
There are three crystal forms of sodium borohydride: α, β and γ. At room temperature, it is α -type NaCl cubic crystal; At 6.3GPa, it is transformed into beta tetragonal crystal, and at 8.9GPa, it is transformed into gamma orthorhombic crystal. [7]
physicochemical property
physical features
White crystalline powder, strong hygroscopicity, easy to absorb water and deliquescence. Soluble in water, liquid ammonia and amine. Soluble in methanol, slightly soluble in ethanol and tetrahydrofuran. Insoluble in ether, benzene and hydrocarbons. Stable in dry air, decomposed in humid air, and decomposed when heated to 500℃. [ 1]
chemical property
1. Because the hydrogen in sodium borohydride is negatively charged (the electronegativity of B is less than that of H), the hydrogen in alcohol and amine substances is positively charged, and BH4- in sodium borohydride can form double hydrogen bonds with the molecules that make up these substances, so sodium borohydride can be dissolved in water, liquid ammonia, alcohol and amine substances. [ 1]
2. Sodium borohydride will react slowly with substances containing hydroxyl groups (such as water and alcohol) to release hydrogen. At the same time, due to the slow reaction, the loss of sodium borohydride is small in a short time, and sodium borohydride can use alkaline solution, methanol and ethanol as solvents. [ 1]
NaBH4+2H2O=NaBO2+4H2↑
NaBH4+4HO-R→B(OR)3 +4H2↑+NaOR
3. Sodium borohydride is an inorganic compound with strong selectivity and reducibility. It is often used as reducing agent in inorganic synthesis and organic synthesis [4] and has good chemical selectivity. It can realize the reduction of carbonyl groups of aldehydes and ketones under very mild conditions to produce primary and secondary alcohols. A small amount of sodium borohydride can reduce nitrile to aldehyde, while an excessive amount of sodium borohydride can reduce nitrile to amine. It can selectively reduce carbonyl and aldehyde groups to hydroxyl groups, and can also reduce carboxyl groups to aldehyde groups, which do not react with esters and amides, and generally do not react with carbon-carbon double bonds and triple bonds.
4. Sodium borohydride has a good reducing effect on aldehydes and ketones. Commonly used solvents are ethanol, tetrahydrofuran, dimethylformamide (DMF), water, etc. Generally, ester groups and amide groups are not reduced, but at high concentration and high temperature, weak carbonyl groups such as ester groups can be reduced by using appropriate solvents or Lewis acid as catalyst.
5. Sodium borohydride can be rapidly decomposed to generate hydrogen under acidic conditions. Hydrogen can not exist stably, but it can exist stably under neutral or alkaline conditions, and it is most stable at pH= 14.
nab H4+h++ 3H2O = h3bo 3+na++ 4h 2↑[5]
6. Sodium borohydride cannot reduce carboxylic acid alone, but it must be used in combination with iodine. Reacting with carboxylic acid until bubbles stop, adding iodine and continuing to exhaust. Subsequently, borate ester formed by decomposition of hydrochloric acid was added to obtain alcohol. [3]
7. After reacting sodium borohydride with anhydrous zinc chloride (dehydrated and dried above 200℃) in anhydrous tetrahydrofuran (THF) for 3 hours, zinc borohydride can be prepared. The solution mixture can be used as zinc borohydride without separation and purification.
Computational chemical data
Reference value of hydrophobic parameter calculation (XLOGP): 0
Number of hydrogen bond donors: 0
Number of hydrogen bond acceptors: 1
Number of rotatable chemical bonds: 0
Number of tautomers: 0
Polar surface area of topological molecules: 0
Number of heavy atoms: 2
Surface charge: 0
Complexity: 2
Atomic number of isotope: 0
Determine the number of atomic solid centers: 0
The number of uncertain atomic solid centers: 0
Determine the number of solid centers of chemical bonds: 0
The number of uncertain chemical bond solid centers: 0
Number of covalent bond units: 2
application area
Sodium borohydride can be used as reducing agent for aldehydes, ketones and acyl chlorides, intermediate for producing potassium borohydride, raw material for producing high-energy fuels such as diborane, foaming agent for plastics industry, treating agent for mercury-containing sewage in paper industry, bleaching agent for paper making, and hydrogenation agent for producing dihydrostreptomycin in pharmaceutical industry. The hydrogen of sodium borohydride shows the valence of-1 here, which has strong reducibility and can reduce inorganic substances with certain oxidation. It is mainly used in organic synthesis to reduce -COOH to -CH2OH, which is called "universal reducing agent". It has stable performance and reduction selectivity. Sodium borohydride provides a very convenient and mild method for organic chemists to reduce aldehydes and ketones. Prior to this, carbonyl compounds were usually reduced by metal/alcohol method, and sodium borohydride can reduce carbonyl groups of aldehydes and ketones under very mild conditions to produce primary and secondary alcohols. As a reducing agent, sodium borohydride can be used for electroless plating of nonferrous metals, especially electroless nickel plating. The most commonly used reducing agent for electroless nickel plating is sodium hypophosphite, and the nickel plated with this reducing agent is mainly nickel-phosphorus alloy. Nickel-boron alloy can be obtained by using sodium borohydride as reducing agent, but the content of boron in the coating is far less than that of phosphorus in another reducing agent coating. In electroless plating, theoretically, the amount of sodium borohydride per unit substance can reduce nickel by 4 times as much as that of sodium hypophosphite, and the addition amount is far less than that of sodium hypophosphite. However, sodium borohydride is easy to decompose, so it is necessary to keep the pH of the plating solution above 12, otherwise it will make the plating solution invalid, and the accumulation of sodium metaborate, the oxidation product of sodium borohydride, will also have an adverse effect on the plating solution. [6]
Related danger
Toxicological data
Acute toxicity: oral LD 50: 18 mg/kg (intracavity) in rats [2]
Main stimulating effects:
It has corrosive effect on skin and mucosa, strong corrosive effect on eyes, and no known sensitization effect. [2]
Hazard characteristics: contact with water, humid air, acid, oxidant, high heat and open flame will cause combustion. [2]
Combustion (decomposition) products: boron oxide, hydrogen. [2]
health hazard
Invasion route: inhalation, ingestion and percutaneous absorption.
Danger: This product has strong irritation to mucosa, upper respiratory tract, eyes and skin. After inhalation, it can lead to death due to laryngeal and bronchial spasm, inflammation and edema, chemical pneumonia and pulmonary edema. Oral erosion of digestive tract. After contact with sodium borohydride, symptoms such as sore throat, cough, shortness of breath, headache, abdominal pain, diarrhea, dizziness, conjunctival congestion and pain appear. Should prevent dust flying, strengthen ventilation or wear protective masks, pay attention to eye protection, wear closed protective glasses, and do not eat, drink or smoke at work. Leave the scene quickly after poisoning, rest in a semi-recumbent position, breathe fresh air, wash your eyes with plenty of water, take off contaminated clothes and wash your whole body. People who enter the digestive tract should gargle immediately, drink plenty of water to induce vomiting, and then send them to hospital for treatment. Wear a filter-type protective mask when leaking, and carefully clean the leaked material. [2]
Emergency treatment
Emergency treatment of leakage
Isolate the leakage and pollution area, set warning signs around it, and cut off the fire source. It is recommended that emergency personnel wear gas masks and chemical protective clothing. Do not directly touch the leakage, do not directly spray water on the leakage, and do not let water enter the packaging container. Collect it with a clean shovel in a dry, clean and covered container and transfer it to a safe place. If there is a large amount of leakage, it should be collected and recycled or discarded after harmless treatment. [2]
protective measure
Respiratory protection: Workers should wear dust masks. Self-contained breathing apparatus is recommended when necessary.
Eye protection: Wear chemical safety glasses.
Physical protection: wear corresponding protective clothing.
Hand protection: Wear protective gloves. [2]
Emergency treatment
Skin contact: Take off contaminated clothes and rinse thoroughly with running water immediately.
Eye contact: lift the eyelid immediately and rinse it with running water or normal saline for at least 15 minutes.
Inhalation: Leave the site and go to a place with fresh air. Keep the respiratory tract unobstructed. Give artificial respiration if necessary. See a doctor.
Intake: Rinse mouth immediately and give milk or egg white. See a doctor. [ 1]
Safety/security information
Safety terminology
Don't inhale dust.
Don't inhale dust.
S26: In case of contact with eyes, immediately flush with plenty of water and seek medical attention.
After accidental contact with eyes, please immediately rinse with plenty of water and seek medical attention.
S36/37/39: Wear appropriate protective clothing, gloves and eye/face protection devices.
Wear appropriate protective clothing, gloves and goggles or a mask.
S45: If you have an accident or feel unwell, seek medical attention immediately (show the label as much as possible.
In case of accident or discomfort, seek medical attention immediately (if possible, show its label).
Risk terminology
R 15: contact with water will release extremely flammable gas.
Release flammable gas when it meets water.
R22: Harmful if swallowed.
Harmful if swallowed.
R23/24/25: Toxic by inhalation, skin contact and swallowing.
Toxic by inhalation, skin contact and swallowing.
R34: Causing burns.
Cause burns.
R43: Skin contact may cause allergy.
Contact with skin may cause allergies.
R53: It may cause long-term adverse effects on aquatic environment.
It may have a long-term adverse impact on the water environment.
Share your world.
I want to share my opinion,
Click publish.
put right
reference data
[1] Tianjin Research Institute of Chemical Industry, Ministry of Chemical Industry, etc. Handbook of chemical products Inorganic chemical products [M]. Tianjin Research Institute of Chemical Industry, Ministry of Chemical Industry. 1982: 43-48
[2] Compilation of the Customs Administration Department of the General Administration of Customs. Guide to the classification of hazardous chemicals [M]. Department of customs administration. 20 17: 83 1-834
[3] Zheng Xue. Production and application of boron compounds [M]. Chemical Industry Press, 2008 ... Baidu Academic [reference date 2020-03- 14]
[4] Bai Yinjuan, lujun, Ma Huairang. Research progress of sodium borohydride in organic synthesis [J]. Applied Chemistry (5): 409-4 15 .. Baidu Academic [citation date: 2020-03- 14]
Xu Dongyan, Zhang Huamin, Ye Wei. Hydrogen production rate of hydrogen production by sodium borohydride hydrolysis [J]. Chemical progress, 2007,019 (010):1598-1605 ... Baidu (the largest Chinese search engine in the world)
Li Ning. Practical Technology of Electroless Plating [M]. Beijing Chemical Industry Press, 2004: 308-3 17. Baidu Academic [reference date 2020-03- 14]
[7] Zhou Gongdu. A Dictionary of Chemistry (Second Edition). Chemical Industry Press.20 20 10/0
[8] The Ministry of Public Security published the 20 17 version of the list of explosive dangerous chemicals. People's Republic of China (PRC) Central People's Government (China) [citation date 2021-1-29].
[9] Measures for Public Security Management of Hazardous Chemicals Easily Made and Exploded (OrderNo. 154 of the Ministry of Public Security). Ministry of Public Security of the People's Republic of China [citation date: 2021-kloc-0/-29]
[10] sodium borohydride. Public Chemistry [citation date 2022-05-25]