| 词条 | Borane |
| 释义 |
| ImageFile = Borane.png | ImageSize = 100px | ImageAlt = Structural formula of borane | ImageFileL1 = Borane-3D-balls.png | ImageSizeL1 = 75px | ImageAltL1 = Ball-and-stick model of borane | ImageFileR1 = Borane-3D-vdW.png | ImageSizeR1 = 75px | ImageAltR1 = Spacefill model of borane | SystematicName = borane (substitutive) trihydridoboron (additive) | OtherNames = {{Unbulleted list|borine|boron trihydride}} |Section1={{Chembox Identifiers | CASNo = 13283-31-3 | CASNo_Ref = | PubChem = 6331 | ChemSpiderID = 6091 | ChemSpiderID_Ref = | ChEBI = 30149 | ChEBI_Ref = | Gmelin = 44 | SMILES = B | StdInChI = 1S/BH3/h1H3 | StdInChI_Ref = | StdInChIKey = UORVGPXVDQYIDP-UHFFFAOYSA-N | StdInChIKey_Ref = }} |Section2={{Chembox Properties | H=3 | B=1 | Appearance = colourless gas | ConjugateAcid = Boronium }} |Section3={{Chembox Thermochemistry | DeltaHf = 106.69 kJ mol−1 | Entropy = 187.88 kJ mol−1 K−1 }} |Section4={{Chembox Structure | MolShape = trigonal planar | PointGroup = D3h | Dipole = 0 D }} |Section5={{Chembox Related | OtherCompounds = {{Unbulleted list|diborane}} }} }}Trihydridoboron, also known as borane or borine, is an unstable and highly reactive molecule with the chemical formula {{Chem|BH|3}}. The preparation of borane carbonyl, BH3(CO), played an important role in exploring the chemistry of boranes, as it indicated the likely existence of the borane molecule.[1] However, the molecular species BH3 is a very strong Lewis acid. Consequently it is highly reactive and can only be observed directly as a continuously produced, transitory, product in a flow system or from the reaction of laser ablated atomic boron with hydrogen.[2] Structure and propertiesBH3 is trigonal planar molecule with D3h symmetry The experimentally determined B–H bond length is 119 pm.[3] In the absence of other chemical species, it reacts with itself to form diborane. Thus, it is an intermediate in the preparation of diborane according to the reaction:[4] BX3 +BH4- → HBX3- + (BH3) (X=F, Cl, Br, I) 2 BH3 → B2H6 The standard enthalpy of dimerization of BH3 is estimated to be −170 kJ mol−1.[4] The boron atom in BH3 has 6 valence electrons. Consequently it is a strong Lewis acid and reacts with any Lewis base, L to form an adduct. BH3 + L → L—BH3 in which the base donates its lone pair, forming a dative covalent bond. Such compounds are thermodynamically stable, but may be easily oxidised in air. Solutions containing borane dimethylsulfide and borane–tetrahydrofuran are commercially available; in tetrahydrofuran a stabilising agent is added to prevent the THF from oxidising the borane.[5] A stability sequence for several common adducts of borane, estimated from spectroscopic and thermochemical data, is as follows: PF3 < CO < Et2O < Me2O < C4H8O < C4H8S < Et2S < Me2S < Py < Me3N < H− BH3 has some soft acid characteristics as sulfur donors form more stable complexes than do oxygen donors.[6] Aqueous solutions of BH3 are extremely unstable.[7][8] {{Chem|BH|3}} + 3{{H2O}} → {{Chem|B(OH)|3}} + {{Chem|3 H|2}} ReactionsMolecular BH3 is believed to be a reaction intermediate in the pyrolysis of diborane to produce higher boranes:[6] B2H6 ⇌ 2BH3 BH3 +B2H6 → B3H7 +H2 (rate determining step) BH3 + B3H7 ⇌ B4H10 B2H6 + B3H7 → BH3 + B4H10 ⇌ B5H11 + H2 Further steps give rise to successively higher boranes, with B10H14 as the most stable end product contaminated with polymeric materials, and a little B20H26. Borane ammoniate, which is produced by a displacement reaction of other borane adducts, eliminates elemental hydrogen on heating to give borazine (HBNH)3.[9] Borane adducts are widely used in organic synthesis for hydroboration, where BH3 adds across the C=C bond in alkenes to give trialkylboranes: (THF)BH3 + 3 CH2=CHR → B(CH2CH2R)3 + THF This reaction is regioselective, Other borane derivatives can be used to give even higher regioselectivity.[12] The product trialkylboranes can be converted to useful organic derivatives. With bulky alkenes one can prepare species such as [HBR2]2, which are also useful reagents in more specialised applications. Borane dimethylsulfide which is more stable than borane–tetrahydrofuran may also be used.[10][11] Hydroboration can be coupled with oxidation to give the hydroboration-oxidation reaction. In this reaction, the boryl group in the generated organoborane is substituted with a hydroxyl group. Reductive amination is an extension of the hydroboration-oxidation reaction, wherein a carbon–nitrogen double bond is undergoing hydroboration. The carbon–nitrogen double bond is created by the reductive elimination of water from a hemiaminal, formed by the addition of an amine to a carbonyl molecule, hence the adjective 'reductive'. Borane(5)Borane(5) is the dihydrogen complex of borane. Its molecular formula is BH5 or possibly BH3(η2-H2).[12] It is only stable at very low temperatures and its existence is confirmed in very low temperature.[13][14] Borane(5) and methanium (CH5+) are isoelectronic.[15] Its conjugate base is the borohydride anion. References1. ^{{Cite journal|last=Burg|first=Anton B.|author2=Schlesinger, H. I.|title=Hydrides of boron. VII. Evidence of the transitory existence of borine ({{Chem|BH|3}}): Borine carbonyl and borine trimethylammine|journal=Journal of the American Chemical Society|date=May 1937|volume=59|issue=5|pages=780–787|doi=10.1021/ja01284a002}} {{Boron compounds}}{{Hydrides by group}}2. ^{{cite journal|last1=Tague|first1=Thomas J.|last2=Andrews|first2=Lester|title=Reactions of Pulsed-Laser Evaporated Boron Atoms with Hydrogen. Infrared Spectra of Boron Hydride Intermediate Species in Solid Argon|journal=Journal of the American Chemical Society|volume=116|issue=11|year=1994|pages=4970–4976|issn=0002-7863|doi=10.1021/ja00090a048}} 3. ^{{cite journal|last1=Kawaguchi|first1=Kentarou|title=Fourier transform infrared spectroscopy of the BH3 ν3 band|journal=The Journal of Chemical Physics|volume=96|issue=5|year=1992|pages=3411|issn=0021-9606|doi=10.1063/1.461942}} 4. ^M. Page, G.F. Adams, J.S. Binkley, C.F. Melius "Dimerization energy of borane" J. Phys. Chem. 1987, vol. 91, pp 2675–2678. {{DOI|10.1021/j100295a001}} 5. ^Hydrocarbon Chemistry, George A. Olah, Arpad Molner, 2d edition, 2003, Wiley-Blackwell {{ISBN|978-0471417828}} 6. ^1 2 {{Greenwood&Earnshaw}} 7. ^{{cite journal|last1=Finn|first1=Patricia|last2=Jolly|first2=William L.|title=Asymmetric cleavage of diborane by water. The structure of diborane dihydrate|journal=Inorganic Chemistry|date=August 1972|volume=11|issue=8|pages=1941–1944|doi=10.1021/ic50114a043}} 8. ^{{cite journal|last1=D'Ulivo|first1=Alessandro|title=Mechanism of generation of volatile species by aqueous boranes|journal=Atomic Spectroscopy|date=May 2010|volume=65|issue=5|pages=360–375|doi=10.1016/j.sab.2010.04.010}} 9. ^{{ cite book | author1 = Housecroft, C. E. | author2 = Sharpe, A. G. | chapter = Chapter 13: The Group 13 Elements | title = Inorganic Chemistry | edition = 3rd | year = 2008 | page = 336 | publisher = Pearson | isbn = 978-0-13-175553-6 }} 10. ^{{cite journal |last= Kollonitisch |first= J. |title= Reductive Ring Cleavage of Tetrahydrofurans by Diborane |journal= J. Am. Chem. Soc. |year= 1961 |volume= 83 |pages= 1515 |doi= 10.1021/ja01467a056}} 11. ^1 {{cite journal|last1=Burkhardt|first1=Elizabeth R.|last2=Matos|first2=Karl|title=Boron reagents in process chemistry: Excellent tools for selective reductions|journal=Chemical Reviews|date=July 2006|volume=106|issue=7|pages=2617–2650|doi=10.1021/cr0406918}} 12. ^{{cite journal|url=https://pubs.rsc.org/en/content/articlelanding/2014/dt/c4dt00019f|title=The stability of η2-H2 borane complexes – a theoretical investigation|first1=Dénes|last1=Szieberth|first2=Tamás|last2=Szpisjak|first3=Gábor|last3=Turczel|first4=László|last4=Könczöl|date=19 August 2014|publisher=|journal=Dalton Transactions|volume=43|issue=36|pages=13571–13577|via=pubs.rsc.org|doi=10.1039/C4DT00019F}} 13. ^{{cite journal|url=https://doi.org/10.1021/ja00090a048|title=Reactions of Pulsed-Laser Evaporated Boron Atoms with Hydrogen. Infrared Spectra of Boron Hydride Intermediate Species in Solid Argon|first1=Thomas J.|last1=Tague|first2=Lester|last2=Andrews|date=1 June 1994|publisher=|journal=Journal of the American Chemical Society|volume=116|issue=11|pages=4970–4976|via=ACS Publications|doi=10.1021/ja00090a048}} 14. ^{{cite journal|url=https://doi.org/10.1063/1.468496|title=The structure and stability of BH5. Does correlation make it a stable molecule? Qualitative changes at high levels of theory|first1=Peter R.|last1=Schreiner|first2=Henry F. |last2=Schaefer III|first3=Paul von Ragué|last3=Schleyer|date=1 June 1994|publisher=|journal=The Journal of Chemical Physics|volume=101|issue=9|pages=7625|via=AIP Publishing|doi=10.1063/1.468496}} 15. ^A Life of Magic Chemistry: Autobiographical Reflections Including Post-Nobel Prize Years and the Methanol Economy, 159p 1 : Boranes |
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