Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and Sodium borohydride: Difference between pages

{{short description|Chemical compound}}

|Watchedfields = changed

|verifiedrevid = 464400313

|ImageFile = Sodium borohydride.svg

|ImageName = Wireframe model of sodium borohydride

|ImageFile1 = sodium borohydride.jpg

|ImageFileL1 = Sodium-3D.png

|ImageFileR1 = Borohydride-3D-vdW.png

| = Sodium

|SystematicName = Sodium boranuide

|Section1 = {{Chembox Identifiers

|InChI = 1S/BH4.Na/h1H4;/q-1;+1

|InChIKey1 = YOQDYZUWIQVZSF-UHFFF

|

CASNo_Ref = {{cascite|correct|CAS}}

|CASNo1_Ref = {{cascite|correct|??}}

|CASNo1 = 15681-89-7

|CASNo1_Comment = (²''D''₄)

|UNII_Ref = {{fdacite|correct|FDA}}

|UNII = 87L0B9CPPA

|UNII1_Ref = {{fdacite|correct|FDA}}

|PubChem = 4311764

|PubChem1 = 23673181

| = (''''₄)

|PubChem2 = 23671303

|PubChem2_Comment = (³''T''₄)

|ChemSpiderID = 26189

|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

|ChemSpiderID1_Ref = {{chemspidercite|correct|chemspider}}

|ChemSpiderID1 = 9052313

|ChemSpiderID1_Comment = (²''D''₄)

|ChemSpiderID2_Ref = {{chemspidercite|correct|chemspider}}

|ChemSpiderID2 = 9312193

|ChemSpiderID2_Comment = (³''T''₄)

|EINECS = 241-004-4

|

MeSHName = Sodium+borohydride

|ChEBI_Ref = {{ebicite|correct|EBI}}

|ChEBI = 50985

|RTECS = ED3325000

|SMILES = [Na+].[BH4-]

|StdInChI_Ref = {{stdinchicite|correct|chemspider}}

|StdInChI = 1S/BH4.Na/h1H4;/q-1;+1

|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

|StdInChIKey = YOQDYZUWIQVZSF-UHFFFAOYSA-N

|Gmelin = 23167}}

|Section2 = {{Chembox Properties

|Formula =

|Appearance = white crystals <br> [[hygroscopic]]

|Na=1|B=1|H=4

|MeltingPtC = 400

| = ()<ref name=/>

|Density = 1.07 g/cm³<ref name=crc>{{cite book | editor= Haynes, William M. | year = 2011 | title = CRC Handbook of Chemistry and Physics | edition = 92nd | publisher = [[CRC Press]] | isbn = 978-1439855119|page= 4.89| title-link = CRC Handbook of Chemistry and Physics }}</ref>

|Solubility =

|SolubleOther = soluble in liquid [[ammonia]], [[amine]]s, [[pyridine]]

|Section3 = {{Chembox Structure

|Structure_ref =<ref>{{cite journal|doi=10.1107/S0365110X54002034|title=The unit cell of potassium borohydride, KBH₄, at 90° K|journal=Acta Crystallogr|year=1954|volume=7|issue=8|author=Ford, P. T. and Powell, H. M. |pages= 604–605|doi-access=free|bibcode=1954AcCry...7..604F }}</ref>

|CrystalStruct = Cubic (NaCl), [[Pearson symbol|cF8 ]]

|SpaceGroup = Fm{{overline|3}}m, No. 225

|LattConst_a = 0.6157 nm

}}

|Section4 = {{Chembox Thermochemistry

|Thermochemistry_ref = <ref>{{cite book |url=https://www.worldcat.org/oclc/930681942 |title=CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data. |date=2016 |others=William M. Haynes, David R. Lide, Thomas J. Bruno |isbn=978-1-4987-5428-6 |edition=2016-2017, 97th |location=Boca Raton, Florida |oclc=930681942}}</ref>

|HeatCapacity = 86.8&nbsp;J·mol⁻¹·K⁻¹

|Entropy = 101.3&nbsp;J·mol⁻¹·K⁻¹

|DeltaHform = −188.6&nbsp;kJ·mol⁻¹

|DeltaGfree = −123.9&nbsp;kJ·mol⁻¹

}}

|Section5 = {{Chembox Hazards

|GHS_ref = <ref>{{GESTIS|Name=Sodium borohydride|ZVG=5740|CAS=16940-66-2|Date=2023-11-09}}</ref>

|GHSPictograms = {{GHS02}}{{GHS06}}{{GHS08}}{{GHS05}}

|GHSSignalWord = Danger

|HPhrases = {{H-phrases|260|301|314|360F}}

<!-- |EUHPhrases = {{EUH-phrases|014}} -->

|PPhrases = {{P-phrases|201|231+232|280|308+313|370+378|402+404}}

|NFPA-H = 3 | NFPA-F = 1 | NFPA-R = 2 | NFPA-S = W

|FlashPtC = 70

|AutoignitionPt = ca.

|AutoignitionPtC = 220

|ExploLimits = 3%

|LD50 = 160&nbsp;mg/kg (Oral – Rat)<BR>230&nbsp;mg/kg (Dermal – Rabbit)

}}

|Section6 = {{Chembox Related

|OtherAnions = [[Sodium cyanoborohydride]]<br />[[Sodium hydride]]<br />[[Sodium borate]]<br />[[Borax]]<br/>[[Sodium aluminum hydride]]

|OtherCations = [[Lithium borohydride]]

|OtherCompounds = [[Lithium aluminium hydride]]<br /> [[Sodium triacetoxyborohydride]]

}}

}}

'''Sodium borohydride''', also known as '''sodium tetrahydridoborate''' and '''sodium tetrahydroborate''',<ref name="google">{{cite book|title=Inorganic Syntheses|author=Busch, D.H.|date=2009|volume=20|publisher=Wiley|isbn=9780470132869|url=https://books.google.com/books?id=XktiIRlSBlkC|page=137|access-date=20 May 2015}}</ref> is an [[inorganic compound]] with the [[chemical formula|formula]] {{chem2|NaBH4|auto=1}} (sometimes written as {{chem2|Na[BH4]}}). It is a white [[crystalline]] solid, usually encountered as an aqueous [[Base (chemistry)|basic solution]]. Sodium borohydride is a [[reducing agent]] that finds application in [[papermaking]] and dye industries. It is also used as a reagent in organic synthesis.<ref name=eros>{{cite book |doi=10.1002/047084289X.rs052.pub3 |chapter=Sodium Borohydride |title=Encyclopedia of Reagents for Organic Synthesis |date=2014 |last1=Banfi |first1=Luca |last2=Narisano |first2=Enrica |last3=Riva |first3=Renata |last4=Stiasni |first4=Nikola |last5=Hiersemann |first5=Martin |last6=Yamada |first6=Tohru |last7=Tsubo |first7=Tatsuyuki |pages=1–13 |isbn=9780470842898 }}</ref>

The compound was discovered in the 1940s by [[Hermann Irving Schlesinger|H. I. Schlesinger]], who led a team seeking volatile uranium compounds.<ref>{{cite journal |author1=Schlesinger, H. I. |author2-link=Herbert C. Brown |author2=Brown, H. C. |author3=Abraham, B. |author4=Bond, A. C. |author5=Davidson, N. |author6=Finholt, A. E. |author7=Gilbreath, J. R. |author8=Hoekstra, H. |author9=Horvitz, L. |author10=Hyde, E. K. |author11=Katz, J. J. |author12=Knight, J. |author13=Lad, R. A. |author14=Mayfield, D. L. |author15=Rapp, L. |author16=Ritter, D. M. |author17=Schwartz, A. M. |author18=Sheft, I. |author19=Tuck, L. D. |author20=Walker, A. O. | title = New developments in the chemistry of diborane and the borohydrides. General summary | journal = [[J. Am. Chem. Soc.]] | year = 1953 | volume = 75 | pages = 186–90 | doi = 10.1021/ja01097a049}}</ref><ref name=sch1945>Hermann I Schlesinger and Herbert C Brown (1945) "[https://patentimages.storage.googleapis.com/99/ba/68/f4852875a53aff/US2461661.pdf Preparation of alkali metal compounds]". US Patent 2461661. Granted on 1949-02-15; expired on 1966-02-15.</ref> Results of this wartime research were declassified and published in 1953.

==Properties==

The compound is soluble in [[Alcohol (chemistry)|alcohol]]s, certain [[ether]]s, and water, although it slowly hydrolyzes.<ref name=eEROS>{{cite encyclopedia|author1=Banfi, L. |author2=Narisano, E. |author3=Riva, R. |author4=Stiasni, N. |author5=Hiersemann, M. |encyclopedia=Encyclopedia of Reagents for Organic Synthesis|year=2004|publisher=J. Wiley & Sons |location=New York|doi=10.1002/047084289X.rs052|isbn=978-0471936237|chapter=Sodium Borohydride}}</ref>

{| class="wikitable floatleft"

|-

! Solvent !! Solubility (g/(100 mL))<ref name=eEROS/>

|-

| [[Methanol|{{chem2|CH3OH}}]] || 13

|-

| [[Ethanol|{{chem2|CH3CH2OH}}]] || 3.16

|-

| [[Diglyme]] || 5.15

|-

| [[Diethyl ether|{{chem2|(CH3CH2)2O}}]] || insoluble

|}

Sodium borohydride is an odorless white to gray-white [[microcrystalline]] powder that often forms lumps. It can be purified by recrystallization from warm (50&nbsp;°C) [[diglyme]].<ref>Brown, H. C. "Organic Syntheses via Boranes" John Wiley & Sons, Inc. New York: 1975. {{ISBN|0-471-11280-1}}. page 260-261</ref> Sodium borohydride is soluble in [[protic solvents]] such as water and lower alcohols. It also reacts with these [[protic solvent]]s to produce {{chem2|H2}}; however, these reactions are fairly slow. Complete decomposition of a methanol solution requires nearly 90&nbsp;min at 20&nbsp;°C.<ref>{{cite journal|last1=Lo|first1=Chih-ting F.|last2=Karan|first2=Kunal|last3=Davis|first3=Boyd R.|title=Kinetic Studies of Reaction between Sodium Borohydride and Methanol, Water, and Their Mixtures|journal=Industrial & Engineering Chemistry Research|volume=46|issue=17|pages=5478–5484|doi=10.1021/ie0608861|year=2007}}</ref> It decomposes in neutral or acidic aqueous solutions, but is stable at pH 14.<ref name=eEROS/>

===Structure===

{{chem2|NaBH4}} is a salt, consisting of the tetrahedral [[Borohydride|{{chem2|[BH4]−}}]] anion. The solid is known to exist as three [[Polymorphism (materials science)|polymorphs]]: ''α'', ''β'' and ''γ''. The stable phase at room temperature and pressure is ''α''-{{chem2|NaBH4}}, which is cubic and adopts an [[Halite structure|NaCl]]-type structure, in the ''Fm{{overline|3}}m'' [[space group]]. At a pressure of 6.3 GPa, the structure changes to the tetragonal ''β''-{{chem2|NaBH4}} (space group ''P42₁c'') and at 8.9 GPa, the orthorhombic ''γ''-{{chem2|NaBH4}} (space group ''Pnma'') becomes the most stable.<ref>{{ cite journal | journal = Appl. Phys. Lett. | year = 2005 | volume = 87 | page = 261916 | doi = 10.1063/1.2158505 | title = Structural transitions in NaBH[sub 4] under pressure | issue = 26 }}</ref><ref>{{ cite journal | journal = Phys. Rev. B | year = 2007 | volume = 76 | page = 092104 | doi = 10.1103/PhysRevB.76.092104 | title = High-pressure phase of NaBH₄: Crystal structure from synchrotron powder diffraction data | issue = 9 | bibcode = 2007PhRvB..76i2104F | last1 = Filinchuk | first1 = Y. | last2 = Talyzin | first2 = A. V. | last3 = Chernyshov | first3 = D. | last4 = Dmitriev | first4 = V. | s2cid = 122588719 }}</ref><ref>{{cite journal | journal = J. Phys. Chem. B | year = 2007 | volume = 111 | issue = 50 | pages = 13873–13876 | doi = 10.1021/jp709840w | pmid = 18031032 | title = Pressure-driven phase transitions in NaBH₄: theory and experiments | last1 = Kim | first1 = E. | last2 = Kumar | first2 = R. | last3 = Weck | first3 = P. F. | last4 = Cornelius | first4 = A. L. | last5 = Nicol | first5 = M. | last6 = Vogel | first6 = S. C. | last7 = Zhang | first7 = J. | last8 = Hartl | first8 = M. | last9 = Stowe | first9 = A. C. | last10 = Daemen | first10 = L. | last11 = Zhao | first11 = Y.}}</ref>

<gallery mode=packed heights=160px>

Alpha-sodium-borohydride-xtal-2007-3D-balls.png|''α''-{{chem2|NaBH4}}

Beta-sodium-borohydride-xtal-2007-3D-balls.png|''β''-{{chem2|NaBH4}}

Gamma-sodium-borohydride-xtal-2007-3D-balls.png|''γ''-{{chem2|NaBH4}}

</gallery>

==Synthesis and handling==

For commercial {{chem2|NaBH4}} production, the Brown-Schlesinger process and the Bayer process are the most popular methods. In the Brown-Schlesinger process sodium borohydride is industrially prepared from [[sodium hydride]] (produced by reacting Na and {{chem2|H2}}) and [[trimethyl borate]] at 250–270&nbsp;°C:

:{{chem2|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.<ref name=Ullmann>{{cite book | last1 = Wietelmann | first1 = Ulrich | last2 = Felderhoff | first2 = Michael | last3 = Rittmeyer | first3 = Peter | chapter = Hydrides | publisher = Wiley-VCH Verlag GmbH & Co. KGaA | doi = 10.1002/14356007.a13_199.pub2 | title = [[Ullmann's Encyclopedia of Industrial Chemistry]] | publication-place = Weinheim, Germany | date = 2002 | isbn = 978-3-527-30673-2 | oclc = 751968805 }}</ref> In the Bayer process, it is produced from inorganic borates, including [[borosilicate glass]]<ref>Schubert, F.; Lang, K.; Burger, A. (1960) "Alkali metal borohydrides" (Bayer). 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&nbsp;°C with or without H pressure"</ref> and [[borax]] ({{chem2|Na2B4O7}}):

:{{chem2|Na2B4O7 + 16 Na + 8 H2 + 7 SiO2 → 4 NaBH4 + 7 Na2SiO3}}

Magnesium is a less expensive reductant, and could in principle be used instead:<ref name="Production 1">Wu, Ying et al. (2004) [https://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/review_chemical_processes.pdf Review of Chemical Processes for the Synthesis of Sodium Borohydride]. Millennium Cell Inc. </ref><ref name="Production 2">{{cite journal|doi=10.3390/inorganics6010010|title=A Recycling Hydrogen Supply System of NaBH4 Based on a Facile Regeneration Process: A Review|journal=Inorganics|volume=6|pages=10|year=2018|last1=Ouyang|first1=Liuzhang|last2=Zhong|first2=Hao|last3=Li|first3=Hai-Wen|last4=Zhu|first4=Min|doi-access=free}}</ref>

:{{chem2|8 MgH2 + Na2B4O7 + Na2CO3 → 4 NaBH4 + 8 MgO + CO2}}

and

:{{chem2|2 MgH2 + NaBO2 → NaBH4 + 2 MgO}}

==Reactivity==

===Organic synthesis===

{{chem2|NaBH4}} [[carbonyl reduction|reduces many organic carbonyls]], depending on the conditions. Most typically, it is used in the laboratory for converting ketones and aldehydes to alcohols.<ref name=eros/> These reductions proceed in two stages, formation of the alkoxide followed by hydrolysis:

:{{chem2|NaBH4 + 4 R2C\dO -> NaO\sCHR2 + B(O\sCHR2)3}}

:{{chem2|NaO\sCHR2 + B(O\sCHR2)3 + 4 H2O -> 4 HO\sCHR2 + NaOH + B(OH)3}}

It also efficiently reduces [[acyl chloride]]s, [[Organic acid anhydride|anhydrides]], α-hydroxy[[Lactonase|lactones]], [[thioester]]s, and [[imine]]s at room temperature or below. It reduces esters slowly and inefficiently with excess reagent and/or elevated temperatures, while carboxylic acids and amides are not reduced at all.<ref>{{Citation|last1=Banfi|first1=Luca|title=Sodium Borohydride|date=2014|encyclopedia=Encyclopedia of Reagents for Organic Synthesis|pages=1–13|publisher=John Wiley & Sons|doi=10.1002/047084289x.rs052.pub3|isbn=9780470842898|last2=Narisano|first2=Enrica|last3=Riva|first3=Renata|last4=Stiasni|first4=Nikola|last5=Hiersemann|first5=Martin|last6=Yamada|first6=Tohru|last7=Tsubo|first7=Tatsuyuki}}</ref>

Nevertheless, an alcohol, often methanol or ethanol, is generally the solvent of choice for sodium borohydride reductions of ketones and aldehydes. The mechanism of ketone and aldehyde reduction has been scrutinized by kinetic studies, and contrary to popular depictions in textbooks, the mechanism does not involve a 4-membered transition state like alkene hydroboration,<ref>{{cite book|title=Organic chemistry|author=Carey, Francis A.|others=Giuliano, Robert M., 1954–|isbn=9780073511214|edition= Tenth |location=New York, NY|oclc=915135847|date = 2016-01-07}}</ref> or a six-membered transition state involving a molecule of the alcohol solvent.<ref>{{cite book|title=Organic chemistry|last=Loudon|first=Marc|date=2009|publisher=Roberts and Co|isbn=9780981519432|edition=5th|location=Greenwood Village, Colo.|oclc=263409353|url-access=registration|url=https://archive.org/details/organicchemistry0000loud}}</ref> Hydrogen-bonding activation is required, as no reduction occurs in an aprotic solvent like [[diglyme]]. However, the rate order in alcohol is 1.5, while carbonyl compound and borohydride are both first order, suggesting a mechanism more complex than one involving a six-membered transition state that includes only a single alcohol molecule. It was suggested that the simultaneous activation of the carbonyl compound and borohydride occurs, via interaction with the alcohol and alkoxide ion, respectively, and that the reaction proceeds through an open transition state.<ref>{{cite journal|last1=Wigfield|first1=Donald C.|last2=Gowland|first2=Frederick W.|date=March 1977|title=The kinetic role of hydroxylic solvent in the reduction of ketones by sodium borohydride. New proposals for mechanism, transition state geometry, and a comment on the origin of stereoselectivity|journal=The Journal of Organic Chemistry|volume=42|issue=6|pages=1108–1109|doi=10.1021/jo00426a048}}</ref><ref>{{cite journal|last=Wigfield|first=Donald C.|date=January 1979|title=Stereochemistry and mechanism of ketone reductions by hydride reagents|journal=Tetrahedron|volume=35|issue=4|pages=449–462|doi=10.1016/0040-4020(79)80140-4|issn=0040-4020}}</ref>

α,β-Unsaturated ketones tend to be reduced by {{chem2|NaBH4}} in a 1,4-sense, although mixtures are often formed. Addition of cerium chloride improves the [[Chemoselectivity|selectivity]] for 1,2-reduction of unsaturated ketones ([[Luche reduction]]). α,β-Unsaturated esters also undergo 1,4-reduction in the presence of {{chem2|NaBH4}}.<ref name="eEROS" />

The {{chem2|NaBH4}}-MeOH system, formed by the addition of [[methanol]] to sodium borohydride in refluxing THF, reduces esters to the corresponding alcohols.<ref name='Costa'>{{cite journal | first1 = Jorge C.S. | last1 = da Costa | first2= Karla C. | last2= Pais | first3= Elisa L. | last3 = Fernandes | first4 = Pedro S. M. | last4 = de Oliveira | first5 = Jorge S. | last5 = Mendonça | first6 =Marcus V. N. | last6 = de Souza | first7 = Mônica A. | last7 = Peralta | first8 = Thatyana R.A. | last8 = Vasconcelos | title = Simple reduction of ethyl, isopropyl and benzyl aromatic esters to alcohols using sodium borohydride-methanol system | journal = [[Arkivoc]] | year = 2006 | pages = 128–133 | url = http://www.arkat-usa.org/ark/journal/2006/I01_General/1523/05-1523A%20as%20published%20mainmanuscript.pdf | access-date = 29 August 2006 }}</ref> 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 eventually decomposes spontaneously to produce hydrogen gas and borates. The same reaction can also occur intramolecularly: an α-ketoester converts into a diol, since the alcohol produced attacks the borohydride to produce an ester of the borohydride, which then reduces the neighboring ester.<ref>{{cite journal|title=Mechanistic rationale for the NaBH₄ reduction of α-keto esters|journal=Tetrahedron Letters|volume=40|issue=28|pages=5193–5196|doi=10.1016/S0040-4039(99)01006-0|year=1999|last1=Dalla|first1=V.|last2=Catteau|first2=J.P.|last3=Pale|first3=P.}}</ref>

The reactivity of {{chem2|NaBH4}} can be enhanced or augmented by a variety of compounds.<ref>{{cite journal|last=Periasamy|first=Mariappan|author2=Thirumalaikumar, Muniappan |title=Methods of enhancement of reactivity and selectivity of sodium borohydride for applications in organic synthesis|journal=Journal of Organometallic Chemistry|year=2000|volume=609|issue=1–2|pages=137–151|doi=10.1016/S0022-328X(00)00210-2}}</ref><ref>{{cite journal|last=Nora de Souza|first=Marcus Vinícius|author2=Alves Vasconcelos |author3=Thatyana Rocha |title=Recent methodologies mediated by sodium borohydride in the reduction of different classes of compounds|journal=Applied Organometallic Chemistry|date=1 November 2006|volume=20|issue=11|pages=798–810|doi=10.1002/aoc.1137}}</ref>

Many additives for modifying the reactivity of sodium borohydride have been developed as indicated by the following incomplete listing.

{| class="wikitable"

|+ Additives for sodium borohydride

|-

!additive!! synthetic applications!!page in Smith and March<ref>{{March6th}}</ref>!!comment

|-

| [[aluminium trichloride|AlCl₃]] || reduction of ketones to methylene ||1837||

|-

| [[bismuth trichloride|BiCl₃]] || converts epoxides to allylic alcohols || 1316||

|-

| [[diphenyl ditelluride|(C₆H₅Te)₂]] || reduction of nitroarenes || 1862

|-

| [[cerium(III) chloride|CeCl₃]] || reduction of ketones in the presence of aldehydes || 1794||[[Luche reduction]]

|-

| [[cobalt dichloride|CoCl₂]] || reduction of azides to amines || 1822||

|-

| [[indium trichloride|InCl₃]] || hydrogenolysis of alkyl bromides, double reduction of unsaturated ketones || 1825, 1793||

|-

| [[lithium chloride|LiCl]] || amine oxides to amines || 1846 ||[[lithium borohydride]]

|-

| [[nickel(II) chloride|NiCl₂]] || deoxygenation of sulfoxides, hydrogenolysis of aryl tosylates, desulfurization, reduction of nitriles || 1851,1831, 991, 1814||[[nickel boride]]

|-

| [[titanium tetrachloride|TiCl₄]] || denitrosatation of [[nitrosamine]]s || 1823||

|-

| [[zinc chloride|ZnCl₂]] || reduction of aldehydes || 1793||

|-

| [[zirconium tetrachloride|ZrCl₄]] || reduction of disulfides, reduction of azides to amines, cleavage of allyl aryl ethers || 1853, 1822, 582||

|-

|}

===Oxidation===

Oxidation with [[iodine]] in [[tetrahydrofuran]] gives [[borane–tetrahydrofuran]], which can reduce carboxylic acids to alcohols.<ref>{{cite book | doi=10.1002/047084289X.rn01598| chapter=Sodium Borohydride and Iodine| title=Encyclopedia of Reagents for Organic Synthesis| date=2013| last1=Brown| first1=Jack D.| last2=Haddenham| first2=Dustin| isbn=978-0471936237}}</ref>

Partial oxidation of [[borohydride]] with iodine gives [[octahydrotriborate]]:<ref>{{cite book |doi=10.1002/9780470132463.ch25|year=1974|last1=Ryschlewitsch|first1=G. E.|last2=Nainan|first2=K. C.|last5=Dewkett|first5=W. J.|last6=Grace|first6=M.|last7=Beall|first7=H.|title=Inorganic Syntheses |chapter=Octahydrotriborate (1-) (&#91;B ₃ H ₈ &#93;) salts |pages=111–118|volume=15|isbn=9780470132463}}</ref>

:{{chem2|3 [BH4]− + I2 → [B3H8]− + 2 H2 + 2 I−}}

===Coordination chemistry===

{{chem2|[BH4]−}} is a [[ligand]] for metal ions. Such borohydride complexes are often prepared by the action of {{chem2|NaBH4}} (or the {{chem2|LiBH4}}) on the corresponding metal halide. One example is the [[titanocene]] derivative:<ref>{{cite book | last1 = Lucas | first1 = C. R. | title = Inorganic Syntheses | chapter = Bis(η ⁵ -Cyclopentadienyl) &#91;Tetrahydroborato(1−)&#93;Titanium | year = 1977 | volume = 17 | page = 93 | doi = 10.1002/9780470132487.ch27 | isbn = 9780470132487}}</ref>

:{{chem2|2 (C5H5)2TiCl2 + 4 NaBH4 → 2 (C5H5)2TiBH4 + 4 NaCl + B2H6 + H2}}

===Protonolysis and hydrolysis===

{{chem2|NaBH4}} reacts with water and alcohols, with evolution of hydrogen gas and formation of the corresponding borate, the reaction being especially fast at low pH. Exploiting this reactivity, sodium borohydride has been studied as a prototypes of the [[direct borohydride fuel cell]].

:{{chem2|NaBH4 + 2 H2O → NaBO2 + 4 H2}} (ΔH &lt; 0)

==Applications==

===Paper manufacture===

The dominant 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.

It has been tested as pretreatment for pulping of wood, but is too costly to be commercialized.<ref name=Ullmann/><ref name=kraftpulping>{{cite journal|author=Istek, A. and Gonteki, E. |title=Utilization of sodium borohydride (NaBH₄) in kraft pulping process|url=http://www.jeb.co.in/journal_issues/200911_nov09/paper_05.pdf|journal=Journal of Environmental Biology|volume=30|issue=6|pages= 951–953 |year=2009|pmid=20329388}}</ref>

===Chemical synthesis===

Sodium borohydride [[organic reduction|reduces]] [[aldehyde]]s and [[ketone]]s to give the related [[Alcohol (chemistry)|alcohol]]s. 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.<ref name=Ullmann/>

===Niche or abandoned applications===

Sodium borohydride has been considered as a way to [[hydrogen storage|store hydrogen]] for [[hydrogen fuel|hydrogen-fueled]] vehicles, as it is safer (being stable in dry air) and more efficient on a weight basis than most other alternatives.<ref name=park2007>Eun Hee Park, Seong Uk Jeong, Un Ho Jung, Sung Hyun Kim, Jaeyoung Lee, Suk Woo Nam, Tae Hoon Lim, Young Jun Park, Yong Ho Yuc (2007): "Recycling of sodium metaborate to borax". ''International Journal of Hydrogen Energy'', volume 32, issue 14, pages 2982-2987. {{doi|10.1016/j.ijhydene.2007.03.029}}</ref><ref name=zpli2003>Z. P. Li, B. H. Liu. K. Arai, N. Morigazaki, S. Suda (2003): "Protide compounds in hydrogen storage systems". ''Journal of Alloys and Compounds'', volumes 356–357, pages 469-474. {{doi|10.1016/S0925-8388(02)01241-0}}</ref> The hydrogen can be released by simple hydrolysis of the borohydride. However, such a usage would need a cheap, relatively simple, and energy-efficient process to recycle the hydrolysis product, [[sodium metaborate]], back to the borohydride. No such process was available as of 2007.<ref name=atiy2007>Hasan K. Atiyeh and Boyd R. Davis (2007): "Separation of sodium metaborate from sodium borohydride using nanofiltration membranes for hydrogen storage application". ''International Journal of Hydrogen Energy'', volume 32, issue 2, pages 229-236. {{doi|10.1016/j.ijhydene.2006.06.003}}</ref>

Although practical temperatures and pressures for hydrogen storage have not been achieved, in 2012 a core–shell [[nanostructure]] of sodium borohydride was used to store, release and reabsorb hydrogen under moderate conditions.<ref name="gary2012">Stuart Gary, "[http://www.abc.net.au/science/articles/2012/08/16/3569478.htm Hydrogen storage no longer up in the air]" in ''[[ABC News and Current Affairs|ABC Science]]'' 16 August 2012, citing {{cite journal |last1=Christian |first1=Meganne |author-link=Meganne Christian |last2=Aguey-Zinsou |first2=Kondo François |year=2012 |title=Core–Shell Strategy Leading to High Reversible Hydrogen Storage Capacity for NaBH₄ |journal=[[ACS Nano]] |volume=6 |issue=9 |pages=7739–7751 |doi=10.1021/nn3030018 |pmid=22873406}}</ref>

Skilled professional conservator/restorers have used sodium borohydride to minimize or reverse [[foxing]] in old books and documents.<ref>{{cite web|url=https://blog.bookstellyouwhy.com/bid/230209/how-to-prevent-and-reverse-foxing-in-rare-books|title=How to Prevent and Reverse Foxing in Rare Books|first=Kristin|last=Masters|website=bookstellyouwhy.com|access-date=3 April 2018}}</ref>

==See also==

Many derivatives and analogues of sodium borohydride exhibit modified reactivity of value in organic synthesis.<ref>Seyden-Penne, J. (1991) [http://rushim.ru/books/mechanizms/reductions.pdf ''Reductions by the Alumino- and Borohydrides in Organic Synthesis'']. VCH–Lavoisier: Paris. p. 9. {{ISBN|978-0-471-19036-3}}</ref>

*[[Sodium triacetoxyborohydride]], a milder reductant owing to the presence of more electron-withdrawing acetate in place of hydride.

*[[Sodium triethylborohydride]], a stronger reductant owing to the presence of electron-donating ethyl groups in place of hydride.

*[[sodium cyanoborohydride]], a milder reductant owing to the presence of more electron-withdrawing cyanide in place of hydride. Useful for reductive aminations.

*[[Lithium borohydride]], a more strongly reducing reagent.

*[[L-selectride]] (lithium tri-''sec''-butylborohydride), a more strongly reducing derivative.

*[[Lithium aluminium hydride]], a more strongly reducing reagent, capable of reducing esters and amides.

==References==

{{Reflist}}

==External links==

*[https://web.archive.org/web/20060209040519/http://www.npi.gov.au/database/substance-info/profiles/15.html National Pollutant Inventory – Boron and compounds]

*[https://archive.today/20130202223031/http://www.sodiumborohydride.com/wcm/products/product_detail.page?display-mode=msds&product=1120465&application=1120785 MSDS for Sodium Borohydride]

*[https://web.archive.org/web/20050305180812/http://merit.hydrogen.co.jp/ Materials & Energy Research Institute Tokyo, Ltd.]

*[https://web.archive.org/web/20051201011849/http://www.sodiumborohydride.com/technical.html Chemo- and stereoselectivity using Borohydride reagents]

*[http://www.sciencelab.com/msds.php?msdsId=9924969 Material Safety Data Sheet] {{Webarchive|url=https://web.archive.org/web/20170710022359/http://www.sciencelab.com/msds.php?msdsId=9924969 |date=2017-07-10 }}

{{Sodium compounds}}

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[[Category:Sodium compounds]]

[[Category:Borohydrides]]

[[Category:Reducing agents]]

[[Category:Substances discovered in the 1940s]]