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Sodium borohydride (Wiki)

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Sodium borohydride
CAS number 16940-66-2 Yes, 15681-89-7 (2D4)
PubChem 4311764 Yes, 23673181 (2D4Yes,23671303 (3T4Yes
ChemSpider 26189 Yes, 9052313 (2D4Yes,9312193 (3T4Yes
EC number 241-004-4
UN number 1426
MeSH Sodium+borohydride
ChEBI CHEBI:50985 Yes
RTECS number ED3325000
Gmelin Reference 23167
Jmol-3D images Image 1
Molecular formula NaBH4
Molar mass 37.83 g/mol
Appearance white crystals
Density 1.0740 g/cm3
Melting point

400 °C[1]

Boiling point

500 °C (dec.)[1]

Solubility inwater soluble, reacts with water
Solubility soluble in liquid ammonia, amines,pyridine
NFPA 704
NFPA 704.svg
Flash point 70 °C
ca. 220 °C
LD50 160 mg/kg
Related compounds
Other anions Sodium cyanoborohydride
Sodium hydride
Sodium borate
Other cations Lithium borohydride
Related compounds Lithium aluminium hydride
Sodium triacetoxyborohydride
 Yes (verify) (what is: Yes/?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium borohydride, also known as sodium tetrahydridoborate, is an inorganic compound with the formula NaBH4. This white solid, usually encountered as a powder, is a versatile reducing agent that finds wide application in chemistry, both in the laboratory and on a technical scale. Large amounts are used for bleaching wood pulp. The compound is insoluble in ether, and soluble in glyme solvents, methanol and water, but reacts with the latter two in the absence of base.[2]

The compound was discovered in the 1940s by H. I. Schlesinger, who led a team that developed metal borohydrides for wartime applications.[3] Their work was declassified and published only in 1953.

Physical properties

Sodium borohydride is an odorless white to gray-white microcrystalline powder which often forms lumps. It is soluble in water, without decomposition, however it reacts vigorously with acid solutions. The salt can be recrystallized by dissolving in warm (50 °C) diglyme followed by cooling the solution.[4]


NaBH4 is a salt, consisting of the tetrahedral BH4- anion. The solid is known to exist as three polymorphs: α, β and γ. The stable phase at room temperature and pressure is α-NaBH4, which is cubic and adopts an NaCl-type structure, in the Fm3m space group. At a pressure of 6.3 GPa, the structure changes to the tetragonal β-NaBH4 (space group P421c) and at 8.9 GPa, the orthorhombic γ-NaBH4 (space group Pnma) becomes the most stable.[5][6][7]


Synthesis and handling

Sodium borohydride is prepared industrially following the original method of Schlesinger: sodium hydride is treated with trimethyl borateat 250–270 °C:

B(OCH3)3 + 4 NaH → NaBH4 + 3 NaOCH3

Millions of kilograms are produced annually, far exceeding the production levels of any other hydride reducing agent.[8] Sodium borohydride can also be produced by the action of NaH on powdered borosilicate glass. [9]


NaBH4 will reduce many organic carbonyls, depending on the precise conditions. Most typically, it is used in the laboratory for converting ketones and aldehydes to alcohols. It will reduce acyl chlorides, thiol esters and imines. Under typical conditions, it will not reduce esters, amides, or carboxylic acids.[2] At room temperature, the only acid derivatives it reduces are acyl chlorides, which are exceptionally electrophilic.

Many other hydride reagents are more strongly reducing. These usually involve replacing hydride with alkyl groups, such as lithium triethylborohydride and L-Selectride (lithium tri-sec-butylborohydride), or replacing B with Al. Variations in the counterion also affect the reactivity of the borohydride.[10]

The reactivity of NaBH4 can be enhanced or augmented by a variety of compounds.[11][12] Oxidation with iodine in tetrahydrofuran gives the BH3-THF complex, which can reduce carboxylic acids.[13] Likewise, the NaBH4-MeOH system, formed by the addition of methanol to sodium borohydride in refluxing THF, reduces esters to the corresponding alcohols.[14] Mixing water or an alcohol with the borohydride converts some of it into unstable hydride ester, which is more efficient at reduction, but the reductant will eventually decompose spontaneously to give hydrogen gas and borates. The same reaction can run also intramolecularly: an α-ketoester converts into a diol, since the alcohol produced will attack the borohydride to produce an ester of the borohydride, which then reduces the neighboring ester.[15] The combination of NaBH4 with carboxylic acids results in the formation of acyloxyborohydride species. These can perform a variety of reductions not normally associated with borohydride chemistry, such as alcohols to hydrocarbons and nitriles to primary amines.[16]

Coordination chemistry

BH4 is a ligand for metal ions. Such borohydride complexes are often prepared by the action of NaBH4 (or the LiBH4) on the corresponding metal halide. One example is the titanocene derivative:[17]

2 (C5H5)2TiCl2 + 4 NaBH4 → 2 (C5H5)2TiBH4 + 4 NaCl + B2H6 + H2

Hydrogen source

In the presence of metal catalysts, sodium borohydride releases hydrogen. Exploiting this reactivity, sodium borohydride is used in prototypes of the direct borohydride fuel cell. The hydrogen is generated for a fuel cell by catalytic decomposition of the aqueous borohydride solution:

NaBH4 + 2 H2O → NaBO2 + 4 H2 (ΔH < 0)


The principal application of sodium borohydride is the production of sodium dithionite from sulfur dioxide: Sodium dithionite is used as a bleaching agent for wood pulp and in the dyeing industry.

Sodium borohydride reduces aldehydes and ketones to give the related alcohols. This reaction is used in the production of various antibiotics including chloramphenicol,dihydrostreptomycin, and thiophenicol. Various steroids and vitamin A are prepared using sodium borohydride in at least one step.

Sodium borohydride has been considered as a solid state hydrogen storage candidate. Although practical temperatures and pressures for hydrogen storage have not been achieved, in 2012 a core–shell nanostructure of sodium borohydride was used successfully to store, release and reabsorb hydrogen under moderate conditions.[18]


Sodium borohydride is a source of basic borate salts which can be corrosive, and hydrogen or diborane, which are both flammable. Spontaneous ignition can result from solution of sodium borohydride in dimethylformamide.

See also


  1. ^ a b MSDS data (carl roth)
  2. ^ a b Banfi, L.; Narisano, E.; Riva, R.; Stiasni, N.; Hiersemann, M. “Sodium Borohydride” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289X.rs052.
  3. ^ Schlesinger, H. I.; Brown, H. C.; Abraham, B.; Bond, A. C.; Davidson, N.; Finholt, A. E.; Gilbreath, J. R.; Hoekstra, H.; Horvitz, L.; Hyde, E. K.; Katz, J. J.; Knight, J.; Lad, R. A.; Mayfield, D. L.; Rapp, L.; Ritter, D. M.; Schwartz, A. M.; Sheft, I.; Tuck, L. D.; Walker, A. O. (1953). "New developments in the chemistry of diborane and the borohydrides. General summary". J. Am. Chem. Soc. 75: 186–90. doi:10.1021/ja01097a049.
  4. ^ Brown, H. C. “Organic Syntheses via Boranes” John Wiley & Sons, Inc. New York: 1975. ISBN 0-471-11280-1. page 260-1.
  5. ^ R. S. Kumar, A. L. Cornelius (2005). "Structural transitions in NaBH[sub 4] under pressure". Appl. Phys. Lett. 87 (26): 261916. doi:10.1063/1.2158505.
  6. ^ Y. Filinchuk, A. V. Talyzin, D. Chernyshov, V. Dmitriev (2007). "High-pressure phase of NaBH4: Crystal structure from synchrotron powder diffraction data". Phys. Rev. B 76 (9): 092104.doi:10.1103/PhysRevB.76.092104.
  7. ^ E. Kim, R. Kumar, P. F. Weck, A. L. Cornelius, M. Nicol, S. C. Vogel, J. Zhang, M. Hartl, A. C. Stowe, L. Daemen, Y. Zhao (2007). "Pressure-driven phase transitions in NaBH4: theory and experiments". J. Phys. Chem. B 111 (50): 13873–13876. doi:10.1021/jp709840w. PMID 18031032.
  8. ^ Peter Rittmeyer, Ulrich Wietelmann “Hydrides” in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_199
  9. ^ Schubert, F.; Lang, K.; Burger, A. “Alkali metal borohydrides” (Bayer), 1960. German patent DE 1088930 19600915 (ChemAbs: 55:120851). Supplement to . to Ger. 1,067,005 (CA 55, 11778i). From the abstract: “Alkali metal borosilicates are treated with alkali metal hydrides in approx. 1:1 ratio at >100 °C with or without H pressure”.
  10. ^ Seyden-Penne, J. "Reductions by the Alumino- and Borohydrides in Organic Synthesis"; VCH–Lavoisier: Paris, 1991.
  11. ^ Periasamy, Mariappan; Thirumalaikumar, Muniappan (2000). "Methods of enhancement of reactivity and selectivity of sodium borohydride for applications in organic synthesis".Journal of Organometallic Chemistry 609 (1–2): 137–151. doi:10.1016/S0022-328X(00)00210-2.
  12. ^ Nora de Souza, Marcus Vinícius; Alves Vasconcelos, Thatyana Rocha (1 November 2006). "Recent methodologies mediated by sodium borohydride in the reduction of different classes of compounds". Applied Organometallic Chemistry 20 (11): 798–810. doi:10.1002/aoc.1137.
  13. ^ Kanth, J. V. Bhaskar; Periasamy, Mariappan (1 September 1991). "Selective reduction of carboxylic acids into alcohols using sodium borohydride and iodine". The Journal of Organic Chemistry 56 (20): 5964–5965. doi:10.1021/jo00020a052.
  14. ^ da Costa, Jorge C.S.; Karla C. Pais, Elisa L. Fernandes, Pedro S. M. de Oliveira, Jorge S. Mendonça, Marcus V. N. de Souza, Mônica A. Peralta, and Thatyana R.A. Vasconcelos (2006). "Simple reduction of ethyl, isopropyl and benzyl aromatic esters to alcohols using sodium borohydride-methanol system" (PDF). Arkivoc: 128–133. Retrieved 2006-08-29.
  15. ^ V. Dalla, J. P. Catteau and P. Pale. Mechanistic rationale for the NaBH4 reduction of α-keto esters. Tetrahedron Letters, Volume 40, Issue 28, 9 July 1999, Pages 5193–5196.
  16. ^ W. Gribble, Gordon (1 January 1998). "Sodium borohydride in carboxylic acid media: a phenomenal reduction system". Chemical Society Reviews 27 (6): 395.doi:10.1039/A827395Z.
  17. ^ C. R. Lucas, “Bis(5-Cyclopentadienyl) [Tetrahydroborato(1-)]Titanium” Inorganic Syntheses, 1977, Volume 17, p.93. doi:10.1002/9780470132487.ch27
  18. ^ Stuart Gary, "Hydrogen storage no longer up in the air" in ABC Science 16 August 2012, citing Christian, Meganne; Aguey-Zinsou, Kondo François (2012). "Core–Shell Strategy Leading to High Reversible Hydrogen Storage Capacity for NaBH4". ACS Nano (American Chemical Society). doi:10.1021/nn3030018. Retrieved 20 August 2012.

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