https://en.wikipedia.org/wiki/Pentaborane(9) Jump to content [ ] Main menu Main menu move to sidebar hide Navigation * Main page * Contents * Current events * Random article * About Wikipedia * Contact us * Donate Contribute * Help * Learn to edit * Community portal * Recent changes * Upload file [wikipe] Wikipedia The Free Encyclopedia Search [ ] Search * Create account * Log in [ ] Personal tools * Create account * Log in Pages for logged out editors learn more * Contributions * Talk Contents move to sidebar hide * (Top) * 1Structure, synthesis, properties * 2Reactions * 3History of its use as a fuel * 4Safety * 5See also * 6References [ ] Toggle the table of contents Pentaborane(9) [ ] 17 languages * l`rby@ * toerkhjh * Deutsch * Ellenika * frsy * Francais * Italiano * Nederlands * Portugues * Russkii * Srpski / srpski * Srpskohrvatski / srpskokhrvatski * Suomi * Svenska * telugu * Ukrayins'ka * Zhong Wen Edit links * Article * Talk [ ] English * Read * Edit * View history [ ] Tools Tools move to sidebar hide Actions * Read * Edit * View history General * What links here * Related changes * Upload file * Special pages * Permanent link * Page information * Cite this page * Get shortened URL * Download QR code * Wikidata item Print/export * Download as PDF * Printable version In other projects * Wikimedia Commons From Wikipedia, the free encyclopedia Pentaborane(9) [220px-Pentaborane] [220px-Pentaborane] Names IUPAC name Pentaborane(9) Other names Pentaborane, pentaboron nonahydride, stable pentaborane Identifiers CAS Number * 19624-22-7^ checkY 3D model (JSmol) * Interactive image ChEBI * CHEBI:33591 ChemSpider * 24765156^ checkY ECHA InfoCard 100.039.253 Edit this at Wikidata EC Number * 243-194-4 Gmelin Reference 26757 RTECS number * RY8925000 UNII * P1F0BN763J^ checkY UN number 1380 CompTox Dashboard ( * DTXSID10880057 Edit this at Wikidata EPA) InChI * InChI=1S/B5H9/c6-1-5-2(6)8-4(5)9-3(5)7-1/h1-5H^ checkY Key: USBVLEBZPMQADS-UHFFFAOYSA-N^ checkY * InChI=1/B5H9/c6-2-1-3(2,6)5(1,8-3)4(1,2,7-2)9-5/h1-5H Key: XPIBKKWNZBDJNI-UHFFFAOYAS SMILES * [H]1[BH]2[H][BH]3[BH]24[BH]1[H][BH]4[H]3 Properties Chemical formula B[5]H[9] Molar mass 63.12 g/mol Appearance Colorless liquid Odor pungent, like sour milk^[1] Density 0.618 g/mL Melting point -46.8 degC (-52.2 degF; 226.3 K) Boiling point 60.1 degC (140.2 degF; 333.2 K) Solubility in water Reacts Solubility Benzene, Cyclohexane, and in other hydrocarbons Vapor pressure 171 mmHg (20degC)^[1] Hazards Occupational safety and health (OHS/OSH): Main hazards Extremely toxic, extremely flammable, can ignite spontaneously, corrosive NFPA 704 four-colored diamond NFPA 704 4 (fire diamond) 4 4 W Flash point 30 degC (86 degF; 303 K) Explosive limits 0.42%-?^[1] Lethal dose or concentration (LD, LC): LD[50] (median dose <50 mg/kg^[2] ) 3 ppm (mouse, 4 hr) 6 ppm (rat, 4 hr) 3.4 ppm (mouse, 4 hr) 35 ppm (dog, 15 min) 244 ppm (monkey, 2 min) LC[50] (median 67 ppm (rat, 5 min) concentration) 40 ppm (mouse, 5 min) 31 ppm (rat, 15 min) 19 ppm (mouse, 15 min) 15 ppm (rat, 30 min) 11 ppm (mouse, 30 min) 10 ppm (rat, 1 hr) 6 ppm (mouse, 1 hr)^[3] NIOSH (US health exposure limits): PEL (Permissible) TWA 0.005 ppm (0.01 mg/m^3)^[1] REL (Recommended) TWA 0.005 ppm (0.01 mg/m^3) ST 0.015 ppm (0.03 mg /m^3)^[1] IDLH (Immediate 1 ppm^[1] danger) Structure Point group C[4v] Dipole moment 2.13 D Except where otherwise noted, data are given for materials in their standard state (at 25 degC [77 degF], 100 kPa). N verify (what is ^checkYN ?) Infobox references Chemical compound Pentaborane(9) is an inorganic compound with the formula B[5]H[9]. It is one of the most common boron hydride clusters, although it is a highly reactive compound. Because of its high reactivity with oxygen, it was once evaluated as rocket or jet fuel. Like many of the smaller boron hydrides, pentaborane is colourless, diamagnetic, and volatile. It is related to pentaborane(11) (B[5]H[11]). Structure, synthesis, properties[edit] Its structure is that of five atoms of boron arranged in a square pyramid. Each boron has a terminal hydride ligand and four hydrides span the edges of the base of the pyramid. It is classified as a nido cage. It was first prepared by Alfred Stock by pyrolysis of diborane at about 200 degC.^[5] An improved synthesis starts from salts of octahydrotriborate (B[3]H-8), which is converted to the bromide B[3]H [7]Br^- using HBr. Pyrolysis of this bromide gives pentaborane.^[6] 5 B[3]H[7]Br^- - 3 B[5]H[9] + 5 Br^- + 4 H[2] In the U.S., pentaborane was produced on a commercial scale by Callery Chemical Company. Above 150 degC, it decomposes, producing hydrogen. Unlike diborane, It is quite stable at room temperature if stored properly. It is much more stable in presence of water than diborane. Pentaborane is a highly polar compound, with a dipole moment of 2.13 D.^[7] It is soluble in hydrocarbons like benzene, and cyclohexane, and in greases including those used in lab equipment. Reactions[edit] The chemistry of pentaborane is extensive.^[8] Halogenation give the symmetrical derivatives B[5]H[8]X, which can be isomerised to place the halide on the base of the square pyramid. With strong bases such as alkyl lithium reagents, it can be deprotonated and the resulting lithium salts react with diverse electrophiles to give substituted derivatives. It is Lewis acidic, forming double adducts with two equivalents of trimethylphosphine. Pentaborane is used for the synthesis of other boron hydride clusters. It is also a precursor to metallaboranes. For example, it reacts with diiron nonacarbonyl to give B[4]H[8]Fe(CO)[3]. History of its use as a fuel[edit] Pentaborane was evaluated by both the U.S. and Russian armed services as a so-called "exotic fuel". Because simple boron compounds burn with a characteristic green flame, the nickname for this fuel in the U.S. industry was "Green Dragon". In terms of heat of combustion, pentaborane surpasses its equivalent carbon compounds because their self-linking element, carbon, weighs at least one atomic mass unit more than an atom of boron, and some boranes contain more hydrogen than the carbon equivalent. The ease of breaking the chemical bonds of the compound is also taken into consideration. Interest in this substance began as a possible fuel for high-speed jets. The propellant mix that would produce the greatest specific impulse for a rocket motor is sometimes given as oxygen difluoride and pentaborane^[citation needed]. During the early years of the space race and the missile gap, American rocket engineers thought they could more cheaply produce a rocket that would compete with the Soviets by using an existing first stage and putting an upper stage with an engine that produces thrust at a very high specific impulse atop it. So projects were begun to investigate this fuel. This pentaborane was considered for use as a fuel by North American Aviation when the XB-70 Valkyrie was in the planning stages, but the aircraft ended up using hydrocarbon fuel instead. Pentaborane was also investigated to be used as a bipropellant with nitrogen tetroxide.^[9] In the Soviet Union, Valentin Glushko used it for the experimental RD-270M rocket engine, under development between 1962 and 1970.^[10] Other boranes were evaluated as fuels, including propylpentaborane (BEF-2) and ethyldecaborane (REF-3).^[11] Diborane and decaborane and their derivates were also investigated. Problems with this fuel include its toxicity and its characteristic of bursting into flame on contact with the air. Furthermore, its exhaust (when used in a jet engine) would also be toxic. The US destroyed its last stockpiles of "Green Dragon" in 2000, long after the pentaborane had been discarded as unworkable. The destruction procedure hydrolyzed the pentaborane with steam to yield hydrogen and a boric acid solution. The long delay occurred in part because there are no industrial plants consuming pentaborane as a feedstock. Instead, army engineers constructed a bespoke system, nicknamed the "Dragon Slayer".^[12] Safety[edit] As one of the compounds that have a NFPA 704 (fire diamond) rating of 4 for every category, it is naturally extremely dangerous. Above 30 degC it can form explosive concentration of vapors with air. Its vapors are heavier than air. It is pyrophoric--can ignite spontaneously in contact with air, when even slightly impure. It can also readily form shock sensitive explosive compounds, and reacts violently with some fire suppressants, notably with halocarbons and water. It is highly toxic and symptoms of lower-level exposure may occur with up to 48 hours delay. Its acute toxicity is comparable to some nerve agents. Occupational exposure limits for pentaborane set by the Occupational Safety and Health Administration and National Institute for Occupational Safety and Health stand at 0.005 ppm (0.01 mg/m^3) over an eight-hour time-weighted average, with a short-term exposure limit of 0.015 ppm (0.03 mg/m^3).^[13] The acute toxicity of pentaborane has caused it to be considered immediately dangerous to life and health, with a limit set at 1 ppm.^[14] See also[edit] * Zip fuel References[edit] 1. ^ ^a ^b ^c ^d ^e ^f NIOSH Pocket Guide to Chemical Hazards. "# 0481". National Institute for Occupational Safety and Health (NIOSH). 2. ^ Pentaborane chemical and safety data 3. ^ "Pentaborane". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH). 4. ^ "NFPA Hazard Rating Information for Common Chemicals". Archived from the original on 17 February 2015. Retrieved 13 March 2015. 5. ^ Stock, A. (1933). The Hydrides of Boron and Silicon. New York: Cornell University Press. ISBN 0-8014-0412-6. 6. ^ Miller, V. R.; Ryschkewitsch, G. E. (1974). Pentaborane(9) (B [5]H[9]). Inorganic Syntheses. Vol. 15. pp. 118-122. doi:10.1002/ 9780470132463.ch26. ISBN 9780470132463. 7. ^ Hrostowski, Henry J.; Myers, Rollie J. (29 December 2004). "The Microwave Spectra, Structure, and Dipole Moment of Stable Pentaborane". The Journal of Chemical Physics. 22 (2): 262. doi: 10.1063/1.1740048. ISSN 0021-9606. 8. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8 . 9. ^ "N[2]O[4]/Pentaborane". Encyclopedia Astronautica. Archived from the original on 8 August 2007. Retrieved 11 August 2007. 10. ^ "RD-270M". Encyclopedia Astronautica. Archived from the original on 26 August 2002. Retrieved 11 August 2007. 11. ^ McDonald, G. (13 November 1957). "Thermal Stability of a Commercial Propyl Pentaborane (HEF-2) in the range 147 to 190 degC" (PDF). National Advisory Committee for Aeronautics. 12. ^ ""Dragon Slayer" neutralizes super fuel" (PDF). Engineer Update . 25 (2). U.S. Army Corps of Engineers. February 2001. 13. ^ CDC - NIOSH Pocket Guide to Chemical Hazards 14. ^ Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs) * v * t * e Boron compounds * BAs Boron pnictogenides * BN * BP * BBr[3] * BCl[3] * BF * BFO Boron halides * BF[3] * BI[3] * B[2]F[4] * B[2]Cl[4] * B(NO[3])[3] Acids * B(OH)[3] * BPO[4] * BH[3] * B[2]H[4] * B[2]H[6] * BH[3]NH[3] * B[4]H[10] Boranes * B[5]H[9] * B[5]H[11] * B[6]H[10] * B[6]H[12] * B[10]H[14] * B[18]H[22] * B[2]O * B[2]O[3] Boron oxides and sulfides * B[2]S[3] * B[6]O Carbides * B[4]C * (BH[2]Me)[2] * BMe[3] Organoboron compounds * BEt[3] * Ac[4](BO[3])[2] * COBH[3] * v * t * e Binary compounds of hydrogen * LiH * NaH Alkali metal * KH (Group 1) hydrides * RbH * CsH * BeH * MgH Monohydrides * CaH * SrH Alkaline * BaH (Group 2) earth hydrides * BeH[2] * MgH[2] Dihydrides * CaH[2] * SrH[2] * BaH[2] * BH[3] * BH * B[2]H[6] * B[2]H[2] * B[2]H[4] Boranes * B[4]H[10] * B[5]H[9] * B[5]H[11] * B[6]H[10] * B[6]H[12] * B[10]H[14] * B[18]H[22] Alanes * AlH[3] Group 13 * Al[2]H[6] hydrides Gallanes * GaH[3] * Ga[2]H[6] Indiganes * InH[3] * In[2]H[6] Thallanes * TlH[3] * Tl[2]H[6] * NhH Nihonanes (predicted) * NhH[3] * Nh[2]H[6] * NhH[5] * alkanes * alkenes * alkynes Hydrocarbons * Cycloalkanes * Cycloalkenes * Cycloalkynes * Annulenes * CH * CH[2] * CH[3] * C[2]H * SiH[4] * Si[2]H[6] * Si[3]H[8] * Si[4]H[10] * Si[5]H[12] Silanes * Si[6]H[14] * Si[7]H[16] * Si[8]H[18] * Si[9]H[20] Group 14 hydrides * Si[10]H[22] * more... Silenes * Si[2]H[4] Silynes * Si[2]H[2] * SiH * GeH[4] * Ge[2]H[6] Germanes * Ge[3]H[8] * Ge[4]H[10] * Ge[5]H[12] Stannanes * SnH[4] * Sn[2]H[6] Plumbanes * PbH[4] * FlH Flerovanes (predicted) * FlH[2] * FlH[4] * NH[3] * N[2]H[4] * N[3]H[5] * N[4]H[6] * N[5]H[7] Azanes * N[6]H[8] * N[7]H[9] * N[8]H[10] * N[9]H[11] * N[10]H[12] * more... * N[2]H[2] Azenes * N[3]H[3] * N[4]H[4] * PH[3] * P[2]H[4] * P[3]H[5] * P[4]H[6] * P[5]H[7] Phosphanes * P[6]H[8] Pnictogen * P[7]H[9] (Group 15) hydrides * P[8]H[10] * P[9]H[11] * P[10]H[12] * more... * P[2]H[2] Phosphenes * P[3]H[3] * P[4]H[4] Arsanes * AsH[3] * As[2]H[4] Stibanes * SbH[3] Bismuthanes * BiH[3] Moscovanes * McH[3] (predicted) * HN[3] * NH * HN[5] * NH[5] (?) H[2]O H[2]O[2] Polyoxidanes H[2]O[3] H[2]O[4] H[2]O[5] more... * H[2]S * H[2]S[2] * H[2]S[3] * H[2]S[4] * H[2]S[5] Polysulfanes * H[2]S[6] * H[2]S[7] * H[2]S[8] * H[2]S[9] * H[2]S[10] Hydrogen * more... chalcogenides (Group 16 hydrides) Selanes * H[2]Se * H[2]Se[2] Tellanes * H[2]Te * H[2]Te[2] Polanes * PoH[2] Livermoranes * LvH[2] (predicted) * HO * HO[2] * HO[3] * H[2]O^+-O^- (?) * HS * HDO * D[2]O * T[2]O HF HCl Hydrogen halides HBr (Group 17 hydrides) HI HAt HTs (predicted) * ScH[2] * YH[2] * YH[3] * YH[6] * YH[9] * LuH[2] * LuH[3] * TiH[2] * TiH[4] * ZrH[2] * ZrH[4] * HfH[2] * HfH[4] * VH * VH[2] * NbH * NbH[2] * TaH * TaH[2] * CrH Transition metal hydrides * CrH[2] * CrH[x] * FeH * FeH[2] * FeH[5] * CoH[2] * RhH[2] * IrH[3] * NiH * PdH[x] (x < 1) * PtH[x] (x< 1) * DsH[2] (predicted) * CuH * RgH (predicted) * ZnH[2] * CdH[2] * HgH * Hg[2]H[2] * HgH[2] * CnH[2] (predicted) * LaH[2] * LaH[3] * LaH[10] * CeH[2] * CeH[3] * PrH[2] * PrH[3] * NdH[2] * NdH[3] * SmH[2] * SmH[3] * EuH[2] * GdH[2] Lanthanide hydrides * GdH[3] * TbH[2] * TbH[3] * DyH[2] * DyH[3] * HoH[2] * HoH[3] * ErH[2] * ErH[3] * TmH[2] * TmH[3] * YbH[2] * LuH[2] * LuH[3] * AcH[2] * ThH[2] * ThH[4] * Th[4]H[15] * PaH[3] * UH[3] * UH[4] * NpH[2] * NpH[3] Actinide hydrides * PuH[2] * PuH[3] * AmH[2] * AmH[3] * CmH[2] * BkH[2] * BkH[3] * CfH[2] * CfH[3] Exotic matter hydrides * PsH * Retrieved from "https://en.wikipedia.org/w/index.php?title= Pentaborane(9)&oldid=1217926141" Categories: * Boranes * Rocket fuels * Foul-smelling chemicals Hidden categories: * Use dmy dates from December 2021 * Chemicals without a PubChem CID * Articles without KEGG source * ECHA InfoCard ID from Wikidata * Articles containing unverified chemical infoboxes * Articles with short description * Short description matches Wikidata * All articles with unsourced statements * Articles with unsourced statements from June 2014 * This page was last edited on 8 April 2024, at 18:07 (UTC). * Text is available under the Creative Commons Attribution-ShareAlike License 4.0 ; additional terms may apply. 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