| Diborane | |
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| IUPAC name | Diborane(6) |
| Identifiers | |
| CAS number | [19287-45-7] |
| RTECS number | HQ9275000 |
| Properties | |
| Molecular formula | B2H6 |
| Molar mass | 27. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to Registry of Toxic Effects of Chemical Substances ( RTECS) is a Database of Toxicity information compiled from the open scientific literature without reference A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 67 g/mol |
| Appearance | colorless gas |
| Density | 1. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 18 g/l, gas (15 °C) |
| Melting point | −165 °C (108. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. 15 K) |
| Boiling point | −92. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid 5 °C (180. 65 K) |
| Solubility in water | Reacts |
| Structure | |
| Coordination geometry | Tetrahedral (for boron) |
| Molecular shape | see text |
| Dipole moment | 0 D |
| Hazards | |
| MSDS | External MSDS |
| EU classification | not listed |
| NFPA 704 |  4 3 3 |
| Flash point | flammable gas |
| Autoignition temperature | 38 °C |
| Related compounds | |
| Related boron compounds | Decaborane BF3 |
| Supplementary data page | |
| Structure and properties | n, εr, etc. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Water is a common Chemical substance that is essential for the survival of all known forms of Life. The term coordination geometry is used in a number of related fields of chemistry and solid state chemistry/physics A tetrahedron (plural tetrahedra) is a Polyhedron composed of four triangular faces three of which meet at each vertex. Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. In physics there are two kinds of dipoles ( Hellènic: di(s- = two- and pòla = pivot hinge An electric dipole is a The debye (symbol D) is a non- SI, CGS unit of electrical dipole moment. A material safety data sheet ( MSDS) is a form containing data regarding the properties of a particular substance This page provides supplementary chemical data on Diborane. Material Safety Data Sheet Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws regulations and administrative provisions relating to the classification packaging and labelling Symbolism The four divisions are typically color-coded with blue indicating level of Health Hazard, red indicating The flash point of a flammable liquid is the lowest Temperature at which it can form an ignitable mixture in air The autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in a normal atmosphere without an external Decaborane, also called decaborane(14, is the Borane with formula B 10 H 14 Boron trifluoride is the Chemical compound with the formula BF3 This page provides supplementary chemical data on Diborane. Material Safety Data Sheet This page provides supplementary chemical data on Diborane. Material Safety Data Sheet The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium Measurement The relative static permittivity εr can be measured for static Electric fields as follows first the Capacitance of a test |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references | |
Diborane is the chemical compound with the formula B2H6. This page provides supplementary chemical data on Diborane. Material Safety Data Sheet This page provides supplementary chemical data on Diborane. Material Safety Data Sheet Ultraviolet-visible spectroscopy or ultraviolet-visible spectrophotometry ( UV/ VIS) involves the Spectroscopy of Photons in the UV-visible Infrared spectroscopy (IR spectroscopy is the subset of Spectroscopy that deals with the Infrared region of the Electromagnetic spectrum. Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is the name given to a technique which exploits the magnetic properties of certain nuclei Mass spectrometry is an analytical technique that identifies the chemical composition of a compound or sample based on the Mass-to-charge ratio of charged particles In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. It is a colorless gas at room temperature with a repulsively sweet odor. Diborane mixes well with air, easily forming explosive mixtures. Diborane will ignite spontaneously in moist air at room temperature. Synonyms include boroethane, boron hydride, and diboron hexahydride.
Diborane is a key boron compound with a variety of applications. The compound is endothermic as indicated by a positive heat of formation, ΔH°f of 36 kJ/mol. Despite its intrinsic instability, diborane is kinetically quite stable and possesses an extensive chemistry.
Contents |
Structure and bonding
Diborane adopts a D2h structure containing four terminal and two bridging hydrogen atoms. The model determined by molecular orbital theory indicates that the bonds between boron and the terminal hydrogen atoms are conventional 2-center, 2-electron covalent bonds. In Chemistry, molecular orbital theory ( MO theory) is a method for determining molecular structure in which Electrons are not assigned to individual The bonding between the boron atoms and the bridging hydrogen atoms is, however, different from that in molecules such as hydrocarbons. Having used two electrons in bonding to the terminal hydrogen atoms, each boron has one valence electron remaining for additional bonding. In chemistry valence electrons are the Electrons contained in the outermost or valence, Electron shell of an Atom. The bridging hydrogen atoms each provide one electron each. Thus the B2H2 ring is held together with four electrons, an example of 3-center-2-electron bonding. A three-center two-electron bond is an electron deficient Chemical bond where three atoms share two electrons This type of bond is sometimes called a 'banana bond'. The lengths of the B-Hbridge bonds and the B-Hterminal bonds are 1. 33 and 1. 19 Å respectively, and this difference in the lengths of these bonds reflects the difference in their strengths, the B-Hbridge bonds being relatively weaker. The structure is isoelectronic with C2H62+, which would arise from the diprotonation of the planar molecule ethene. Two or more molecular entities ( Atoms Molecules Ions are described as being isoelectronic with each other if they have the same number of Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond. Diborane is one of many compounds with such unusual bonding. [1]
Of the other elements in Group 13, only gallium is known to form a similar compound, digallane, Ga2H6. Aluminium forms a polymeric hydride. No hydrides of indium and thallium have yet been found. [2]
Production and syntheses
Diborane is so central and has been studied so often that many syntheses exist. Most preparations entail reactions of hydride donors with boron halides or alkoxides. The industrial synthesis involves the reduction of BF3:
Two laboratory methods start from boron trichloride with lithium aluminium hydride or from boron trifluoride ether solution with sodium borohydride. Sodium hydride is the Chemical compound with the formula NaH It is primarily used as a strong base in Organic synthesis. Sodium fluoride is the Chemical compound with the formula NaF Boron trichloride is a Chemical compound with the formula BCl3 Lithium aluminium hydride ( Li[[Aluminium Al]] H4) commonly abbreviated to LAH, is a Reducing agent used in Organic synthesis Boron trifluoride is the Chemical compound with the formula BF3 Sodium borohydride, also known as sodium tetrahydroborate, has the Chemical formula Na[[boron B]] H 4 Both methods yield in up to 30% of diborane:
- 4 BCl3 + 3 LiAlH4 → 2 B2H6 + 3 LiAlCl4
- 4 BF3 + 3 NaBH4 → 2 B2H6 + 3 NaBF4
Older methods entail the direct reaction of borohydride salts with a non-oxidizing acid, such as phosphoric acid or dilute sulfuric acid. Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Phosphoric acid, also known as orthophosphoric acid or phosphoric(V acid, is a mineral (inorganic acid having the Chemical formula Sulfuric (or sulphuric acid, H 2 S[[oxygen O]]4 is a strong Mineral acid.
- 2 BH4− + 2 H+ → 2H2 + B2H6
Similarly, oxidation of borohydride salts has been demonstrated and remains convenient for small scale preparations:
Reactions
Diborane is a highly reactive and versatile reagent that has a large number of applications. Sodium iodide is a white Crystalline Salt with Chemical formula Na[[Iodine I]] used in radiation detection treatment of Iodine deficiency Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 [3] Its dominating reaction pattern involves formation of adducts with Lewis bases. Often such initial adducts proceed rapidly to give other products. It reacts with ammonia to form ammonia borane or the diammoniate of diborane, DADB, depending on the conditions used. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Ammonia borane (or borazane is the Chemical compound with the formula H3NBH3 Diborane also reacts readily with alkynes to form substituted alkene products which will readily undergo further addition reactions. Alkynes are Hydrocarbons that have at least one Triple bond between two Carbon atoms with the formula CnH2n-2. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon An addition reaction, in Chemistry, is in its simplest terms an Organic reaction where two or more molecules combine to form a larger one
Diborane reacts with water to form hydrogen and boric acid. Boric acid, also called boracic acid or orthoboric acid or Acidum Boricum, is a mild Acid often used as an Antiseptic, Insecticide
The compound forms complexes with Lewis bases. Notable are the complexes with THF and dimethyl sulfide, both liquid compounds are popular reducing agents in organic chemistry. "THF" redirects here For other uses see THF (disambiguation. Dimethyl sulfide (DMS or methylthiomethane is an organosulfur compound with the formula (CH32S Organic chemistry is a discipline within Chemistry which involves the scientific study of the structure properties composition reactions, and preparation In these 1:1 complexes, boron assumes a tetrahedral geometry, being bound to three hydrides and the Lewis base (THF or Me2S). The THF adduct is usually prepared as a 1:5 solution in THF. "THF" redirects here For other uses see THF (disambiguation. The latter is indefinitely stable when stored under nitrogen at room temperature.
Reagent in organic synthesis
Diborane is the central organic synthesis reagent for hydroboration, whereby alkenes add across the B-H bonds to give trialkylboranes:
- (THF)BH3 + 3 CH2=CHR → B(CH2CH2R)3 + THF
This reaction is regioselective, and the product trialkylboranes can be converted to useful organic derivatives. Organic synthesis is a special branch of Chemical synthesis and is concerned with the construction of Organic compounds via Organic reactions Organic In Organic chemistry, the hydroboration-oxidation reaction is a two-step organic chemical reaction that converts an Alkene into a neutral Alcohol With bulky alkenes one can prepare species such as [HBR2]2, which are also useful reagents in more specialized applications.
Diborane is used as a reducing agent roughly complementary to the reactivity of lithium aluminium hydride. A reducing agent (also called a reductant or reducer) is the element or a compound in a Redox (reduction-oxidation reaction (see Electrochemistry Lithium aluminium hydride ( Li[[Aluminium Al]] H4) commonly abbreviated to LAH, is a Reducing agent used in Organic synthesis The compound readily reduces carboxylic acids to the corresponding alcohols, whereas ketones react only sluggishly. Carboxylic acids are Organic acids characterized by the presence of a Carboxyl group, which has the formula -C(=OOH usually written -COOH or -CO2H In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon A ketone (pronounced as key tone) is either the Functional group characterized by a Carbonyl group (O=C linked to two other Carbon atoms or
History
Diborane was first synthesised in the 19th century by hydrolysis of metal borides, but it was never analysed. From 1912 to 1936, the major pioneer in the chemistry of boron hydrides, Alfred Stock, undertook his research that led to the methods for the synthesis and handling of the highly reactive, volatile, and often toxic boron hydrides. Alfred Stock ( July 16 1876 – August 12 1946) was a German inorganic chemist. He proposed the first ethane-like structure of diborane. [4] Electron diffraction from S. Electron diffraction is a technique used to study matter by firing Electrons at a sample and observing the resulting Interference pattern H. Bauer appeared to initially supported his proposed structure. [5][6]
Because of a personal communication with L. Pauling(who supported the ethane-like structure), H. I. Schlessinger did not specifically discuss 3-center-2-electron bonding in his then classic review in the early 1940's. Linus Carl Pauling (February 28 1901 – August 19 1994 was an American Scientist, Peace activist, Author and educator. Hermann Irving Schlesinger ( October 11, 1882 - October 3, 1960) was an American inorganic chemist, working in Boron A three-center two-electron bond is an electron deficient Chemical bond where three atoms share two electrons [7] The review does, however, discuss the C2v structure in some depth, "It is to be recognized that this formulation easily accounts for many of the chemical properties of diborane. . . "
In 1943 an undergraduate student at Balliol College, Oxford, H. Christopher Longuet-Higgins, published the currently accepted structure together with R. P. Bell. Balliol College (ˈbeɪlɪəl founded in 1263 is one of the constituent colleges of the University of Oxford in England. Hugh Christopher Longuet-Higgins FRS was both a theoretical chemist and a cognitive scientist. Ronnie Bell was a British Chemist who worked in the Physical Chemistry Laboratory at Oxford University, England. [8] This structure had already been described in 1921. [9][10][11] The years following the Longuet-Higgins/Bell proposal witnessed a colorful discussion about the correct structure. The debate ended with the electron diffraction measurement in 1951 by K. Hedberg and V. Schomaker, with the confirmation of the structure shown in the schemes on this page. [12]
William Nunn Lipscomb, Jr. William Nunn Lipscomb Jr (born December 9, 1919) is an American inorganic chemist, working in experimental and Theoretical chemistry further confirmed the molecular structure of boranes using X-ray crystallography in the 1950's, and developed theories to explain its bonding. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. Crystallography is the experimental science of determining the arrangement of Atoms in Solids In older usage it is the scientific study of Crystals The Later, he applied the same methods to related problems, including the structure of carboranes on which he directed the research of future Nobel Prize winner Roald Hoffmann. The Nobel Prize (Nobelpriset (Nobelprisen is a Swedish prize established in the 1895 will of Swedish chemist Alfred Nobel; it was first awarded in Peace, Literature Roald Hoffmann (born July 18, 1937) is an American theoretical Chemist who won the 1981 Nobel Prize in Chemistry. Lipscomb received The Nobel Prize in Chemistry in 1976 for his efforts. The Nobel Prize in Chemistry (Nobelpriset i kemi is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of Chemistry.
Other uses
Diborane is used in rocket propellants, as a rubber vulcaniser, as a catalyst for hydrocarbon polymerisation, as a flame-speed accelerator, and as a doping agent for the production of semiconductors. Rocket propellant is mass that is stored usually in some form of Propellant tank prior to being used as the propulsive mass that is ejected from a rocket engine in the form Vulcanization (or Vulcanisation refers to a specific curing process of Rubber involving high heat and the addition of Sulfur or other equivalent curatives Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. In Polymer chemistry, polymerization is a process of reacting Monomer Molecules together in a Chemical reaction to form three-dimensional networks In Semiconductor production doping is the process of intentionally introducing impurities into an extremely pure (also referred to as intrinsic) semiconductor to It is also an intermediate in the production of highly pure boron for semiconductor production. Boron (ˈbɔərɒn is a Chemical element with Atomic number 5 and the chemical symbol B.
Safety
The toxic effects of diborane are primarily due to its irritant properties. Short-term exposure to diborane can cause a sensation of tightness of the chest, shortness of breath, cough, and wheezing. These signs and symptoms can occur immediately or be delayed for up to 24 hours. Skin and eye irritation can also occur. Studies in animals have shown that diborane causes the same type of effects observed in humans.
People exposed for a long time to low amounts of diborane have experienced respiratory irritation, seizures, fatigue, drowsiness, confusion, and occasional transient tremors. An epileptic seizure is caused by excessive and/or hypersynchronous electrical Neuronal activity and is usually self-limiting Somnolence (or " drowsiness " is a state of near- Sleep, a strong desire for sleep or sleeping for unusually long periods (c
References
- ^ Laslo P (2000). "A Diborane Story". Angewandte Chemie International Edition 39: 2071-2072. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. abstract
- ^ Downs, Anthony J. ; Colin R. Pulham (1994). "The hydrides of aluminium, gallium, indium and thallium: A re-evaluation". Chemical Society Reviews 23 (3): 175 - 184. Cambridge: Royal Society of Chemistry. The Royal Society of Chemistry (RSC is a Learned society ( Professional association) in the United Kingdom with the goal of "advancing the ISSN 0306-0012. An International Standard Serial Number ( ISSN) is a unique eight-digit number used to identify a print or electronic Periodical publication.
- ^ Mikhailov BM (1962). "The Chemistry of Diborane". Russian Chemical Review 31 (31): 207-224. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Stock A. (1933). The Hydrides of Boron and Silicon. New York: Cornell University Press.
- ^ Bauer S. H. (1937). "The Structure of Diborane". Journal of the American Chemical Society 59: 1096. The Journal of the American Chemical Society (usually abbreviated as J doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Bauer S. H. (1942). "Structures and Physical Properties of the Hydrides of Boron and of their Derivatives". Chemical Reviews 31: 43-75. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Schlesinger H. I. , Burg A. B. (1942). "Recent Developments in the Chemistry of the Boron Hydrides". Chemical Reviews 31: 1-41. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Longuet-Higgins, H. C. , Bell, R. P. (1943). "The structure of the boron hydrides". Journal of the Chemical Society: 250-255. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Dilthey W. (1921). "". Zeitschriffte fuer Angewandte Chemie 34: 594.
- ^ Nekrassov BV (1940). "". J Gen Chem USSR 10: 1021.
- ^ Nekrassov BV (1940). "". J Gen Chem USSR 10: 1056.
- ^ Hedberg K, Schomaker V (1951). "A Reinvestigation of the Structures of Diborane and Ethane by Electron Diffraction". Journal of the American Chemical Society 73: 1482-1487. The Journal of the American Chemical Society (usually abbreviated as J doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
Further reading
H. C. Brown "Organic Synthesis via Boranes" John Wiley, New York, 1975. ISBN 0-471-11280-1.
External links
- International Chemical Safety Card 0432
- Computational Chemistry Wiki
- National Pollutant Inventory - Boron and compounds
- NIOSH Pocket Guide to Chemical Hazards
- U.S. EPA Acute Exposure Guideline Levels
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