“Sodium borohydride”的意思、由来-开放百科全书

The compound was discovered in the 1940s by H. I. Schlesinger, who led a team seeking volatile uranium compounds.^[5] Results of this wartime research were declassified and published in 1953.

Properties

Sodium borohydride is an odorless white to gray-white microcrystalline powder that often forms lumps. It can be purified by recrystallization from warm (50 °C) diglyme.^[6] Sodium borohydride is soluble in protic solvents such as water and lower alcohols. It also reacts with these protic solvents to produce H₂, however, these reactions are fairly slow. Complete decomposition of a methanol solution requires nearly 90 min at 20 °C.^[7] It will decompose in neutral or acidic aqueous solutions, but is stable at pH 14.^[4]

Structure

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.^[8]^[9]^[10]

Synthesis and handling

For commercial 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 following the original method of Schlesinger: sodium hydride (produced by reacting Na and H₂) is treated with trimethyl borate at 250–270 °C:

Millions of kilograms are produced annually, far exceeding the production levels of any other hydride reducing agent.^[11] Sodium borohydride can also be produced by the action of NaH on powdered borosilicate glass.^[12]

Different from it, the Bayer process is based on the reaction among borax (Na₂B₄O₇), Na, H₂, and silicon oxide (SiO₂) at 700 °C to synthesize NaBH₄:

There is currently an effort to modify the Bayer Process by employing the less expensive reducing metal magnesium (Mg) in place of sodium. Reactions such as:

are promising modifications to the Bayer Process, but have not been developed far enough to exhibit both high yield and fast reaction rates.^[13]^[14]

Reactivity

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 efficiently reduce acyl chlorides, anhydrides, α-hydroxylactones, thioesters, and imines at room temperature or below. It will reduce esters slowly and inefficiently with excess reagent and/or elevated temperatures, while carboxylic acids and amides are not reduced at all.^[15] NaBH₄ reacts with water and alcohols, with evolution of hydrogen gas and formation of the borate salt, the reaction being especially fast at low pH.

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,^[16] or a six-membered transition state involving a molecule of the alcohol solvent.^[17] 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.^[18]^[19]

α,β-Unsaturated ketones tend to be reduced by NaBH₄ in a 1,4-sense, although mixtures are often formed. Addition of cerium chloride as an additive greatly improves the selectivity for 1,2-reduction of unsaturated ketones (Luche reduction). α,β-Unsaturated esters also undergo 1,4-reduction in the presence of NaBH₄.^[4]

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.^[20]

The reactivity of NaBH₄ can be enhanced or augmented by a variety of compounds.^[21]^[22] Oxidation with iodine in tetrahydrofuran gives the borane–tetrahydrofuran complex, which can reduce carboxylic acids.^[23] Likewise, the NaBH₄-MeOH system, formed by the addition of methanol to sodium borohydride in refluxing THF, reduces esters to the corresponding alcohols.^[24] 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.^[25] The combination of NaBH₄ with carboxylic acids results in the formation of acyloxyborohydride species, such as STAB. These can perform a variety of reductions not normally associated with borohydride chemistry, such as alcohols to hydrocarbons and nitriles to primary amines.^[26]

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:^[27]

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:

Applications

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 is used as reducing agent in the synthesis of gold nanoparticles.^[28]

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.^[29]

Sodium borohydride can be used to reduce foxing in old books and documents.^[30]

Safety

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

References

1. ^¹MSDS data (carl roth)
2. ^{{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|accessdate=20 May 2015}}
3. ^Istek, A. and Gonteki, E. "Utilization of sodium borohydride (NaBH4) in kraft pulping process." Retrieved online on 25 September 2014 at http://www.jeb.co.in/journal_issues/200911_nov09/paper_05.pdf.
4. ^¹²³{{cite encyclopedia|authors=Banfi, L.; Narisano, E.; Riva, R.; Stiasni, N.; 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}}
5. ^{{cite journal | author = 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. | 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}}
6. ^Brown, H. C. “Organic Syntheses via Boranes” John Wiley & Sons, Inc. New York: 1975. {{ISBN|0-471-11280-1}}. page 260-1.
7. ^{{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}}
8. ^{{ cite journal |author1=R. S. Kumar |author2=A. L. Cornelius | 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 }}
9. ^{{ cite journal |author1=Y. Filinchuk |author2=A. V. Talyzin |author3=D. Chernyshov |author4=V. Dmitriev | 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 }}
10. ^{{ cite journal |author1=E. Kim |author2=R. Kumar |author3=P. F. Weck |author4=A. L. Cornelius |author5=M. Nicol |author6=S. C. Vogel |author7=J. Zhang |author8=M. Hartl |author9=A. C. Stowe |author10=L. Daemen |author11=Y. Zhao | 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 }}
11. ^¹Peter Rittmeyer, Ulrich Wietelmann "Hydrides" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a13_199}}
12. ^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".
13. ^Review of Chemical Processes for the Synthesis of Sodium Borohydride. Millennium Cell Inc. 2004, https://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/review_chemical_processes.pdf
14. ^Liuzhang Ouyang et al. A Recycling Hydrogen Supply System of NaBH4 Based on a Facile Regeneration Process: A Review. Inorganics 2018, 6(1), 10; https://doi.org/10.3390/inorganics6010010 , http://www.mdpi.com/2304-6740/6/1/10/pdf (free access).
15. ^{{Citation|last=Banfi|first=Luca|title=Sodium Borohydride|date=2014-10-20|work=Encyclopedia of Reagents for Organic Synthesis|pages=1–13|publisher=John Wiley & Sons, Ltd|language=en|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}}
16. ^{{Cite book|title=Organic chemistry|last=1937-|first=Carey, Francis A.|others=Giuliano, Robert M., 1954-|isbn=9780073511214|edition= Tenth |location=New York, NY|oclc=915135847|date = 2016-01-07}}
17. ^{{Cite book|title=Organic chemistry|last=Marc.|first=Loudon, G.|date=2009|publisher=Roberts and Co|isbn=9780981519432|edition= 5th |location=Greenwood Village, Colo.|oclc=263409353}}
18. ^{{Cite journal|last=Wigfield|first=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|language=en|volume=42|issue=6|pages=1108–1109|doi=10.1021/jo00426a048|issn=0022-3263}}
19. ^{{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}}
20. ^Seyden-Penne, J. "Reductions by the Alumino- and Borohydrides in Organic Synthesis"; VCH–Lavoisier: Paris, 1991.
21. ^{{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|url=http://www.sciencedirect.com/science/article/pii/S0022328X00002102}}
22. ^{{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}}
23. ^{{cite journal|last=Kanth|first=J. V. Bhaskar|author2=Periasamy, Mariappan |title=Selective reduction of carboxylic acids into alcohols using sodium borohydride and iodine|journal=The Journal of Organic Chemistry|date=1 September 1991|volume=56|issue=20|pages=5964–5965|doi=10.1021/jo00020a052}}
24. ^{{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 | accessdate = 29 August 2006 }}
25. ^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.
26. ^{{cite journal|last=W. Gribble|first=Gordon|title=Sodium borohydride in carboxylic acid media: a phenomenal reduction system|journal=Chemical Society Reviews|date=1 January 1998|volume=27|issue=6|pages=395|doi=10.1039/A827395Z|url=http://pubs.rsc.org/en/Content/ArticleLanding/1998/CS/a827395z}}
27. ^{{cite book | last1 = Lucas | first1 = C. R. | year = 1977 | title = Bis(5-Cyclopentadienyl) [Tetrahydroborato(1-)]Titanium | url = | journal = Inorganic Syntheses | volume = 17 | issue = | page = 93 | doi = 10.1002/9780470132487.ch27 | isbn = 9780470132487 }}
28. ^Low and Bansal, 2009
29. ^Stuart Gary, "Hydrogen storage no longer up in the air" in ABC Science 16 August 2012, citing {{cite journal |last1= Christian|first1= Meganne|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}}
30. ^{{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|date=|website=bookstellyouwhy.com|accessdate=3 April 2018}}