Chromium(III) bromide

Last updated
Chromium(III) bromide
Kristallstruktur Bismut(III)-iodid.png
Names
IUPAC name
Chromium(III) bromide
Other names
  • Chromic bromide
  • Chromium bromide
  • Chromium tribromide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.068 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 233-088-6
PubChem CID
UNII
  • InChI=1S/3BrH.Cr/h3*1H;/q;;;+3/p-3
    Key: UZDWIWGMKWZEPE-UHFFFAOYSA-K
  • [Cr+3].[Br-].[Br-].[Br-]
Properties
CrBr3
Molar mass 291.708 g·mol−1
AppearanceBlack lustrous crystals; green in transmitted light, reddish in reflected light [1]
Density 4.25 g/cm3 [2]
Melting point 1,130 °C (2,070 °F; 1,400 K) (anhydrous) [2]
79 °C (hexahydrate)
anhydrous: insoluble in cold water, soluble with addition of Chromium(II) ion salts, [1] soluble in hot water; [2] hexahydrate: highly soluble [2]
Structure
trigonal
Hazards
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 1 mg/m3 [3]
REL (Recommended)
TWA 0.5 mg/m3 [3]
IDLH (Immediate danger)
250 mg/m3 [3]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Chromium(III) bromide is an inorganic compound with the chemical formula Cr Br 3. It is a dark colored solid that appears green in transmitted light but red with reflected light. It is used as a precursor to catalysts for the oligomerization of ethylene.

Contents

Synthesis

The compound is prepared in a tube furnace by the reaction of bromine vapor and chromium powder at 1000 °C. It is purified by extracting with absolute diethyl ether to remove any CrBr2, and is subsequently washed with absolute diethyl ether and absolute ethanol. [1]

Analogous to the behavior of related chromium(III) halides, the tribromide dissolves in water to give CrBr3(H2O)3 only upon the addition of catalytic amounts of a reducing agent, which generates CrBr2. [1] The reducing agent generates chromous bromide on the surface of the solid, which dissolves and re-oxidizes to Cr(III).[ citation needed ]

Reactions

Chromium(III) bromide is reduced by hydrogen gas at 350-400 °C to give chromium(II) bromide: [1]

2 CrBr3 + H2 → 2 CrBr2 + 2 HBr

Related Research Articles

<span class="mw-page-title-main">Bromine</span> Chemical element, symbol Br and atomic number 35

Bromine is a chemical element; it has symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between those of chlorine and iodine. Isolated independently by two chemists, Carl Jacob Löwig and Antoine Jérôme Balard, its name was derived from the Ancient Greek βρῶμος (bromos) meaning "stench", referring to its sharp and pungent smell.

Hydrobromic acid is an aqueous solution of hydrogen bromide. It is a strong acid formed by dissolving the diatomic molecule hydrogen bromide (HBr) in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at 124.3 °C (255.7 °F) and contains 47.6% HBr by mass, which is 8.77 mol/L. Hydrobromic acid is one of the strongest mineral acids known.

<span class="mw-page-title-main">Hydrogen bromide</span> Chemical compound

Hydrogen bromide is the inorganic compound with the formula HBr. It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room temperature. Aqueous solutions that are 47.6% HBr by mass form a constant-boiling azeotrope mixture that boils at 124.3 °C (255.7 °F). Boiling less concentrated solutions releases H2O until the constant-boiling mixture composition is reached.

<span class="mw-page-title-main">Chromium(III) chloride</span> Chemical compound

Chromium(III) chloride (also called chromic chloride) is an inorganic chemical compound with the chemical formula CrCl3. It forms several hydrates with the formula CrCl3·nH2O, among which are hydrates where n can be 5 (chromium(III) chloride pentahydrate CrCl3·5H2O) or 6 (chromium(III) chloride hexahydrate CrCl3·6H2O). The anhydrous compound with the formula CrCl3 are violet crystals, while the most common form of the chromium(III) chloride are the dark green crystals of hexahydrate, CrCl3·6H2O. Chromium chlorides find use as catalysts and as precursors to dyes for wool.

<span class="mw-page-title-main">Chromium trioxide</span> Chemical compound

Chromium trioxide (also known as chromium(VI) oxide or chromic anhydride) is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a dark-purple solid under anhydrous conditions and bright orange when wet. The substance dissolves in water concomitant with hydrolysis. Millions of kilograms are produced annually, mainly for electroplating. Chromium trioxide is a powerful oxidiser, a mutagen, and a carcinogen.

<span class="mw-page-title-main">Iron(III) bromide</span> Chemical compound

Iron(III) bromide is the chemical compound with the formula FeBr3. Also known as ferric bromide, this red-brown odorless compound is used as a Lewis acid catalyst in the halogenation of aromatic compounds. It dissolves in water to give acidic solutions.

<span class="mw-page-title-main">Chromyl chloride</span> Chemical compound

Chromyl chloride is an inorganic compound with the formula CrO2Cl2. It is a reddish brown compound that is a volatile liquid at room temperature, which is unusual for transition metal compounds.

<span class="mw-page-title-main">Arsenic tribromide</span> Chemical compound

Arsenic tribromide is an inorganic compound with the formula AsBr3, it is a bromide of arsenic. Arsenic is a chemical element that has the symbol As and atomic number 33. This pyramidal molecule is the only known binary arsenic bromide. AsBr3 is noteworthy for its very high refractive index of approximately 2.3. It also has a very high diamagnetic susceptibility. It is a poisonous metalloid that has many allotropic forms: yellow and several black and gray forms (metalloids), orthorhombic prisms, colorless rhombic crystals are a few that are seen. Bromine is a halogen element with the symbol Br and atomic number 35. Diatomic bromine does not occur naturally, but bromine salts can be found in crustal rock.

<span class="mw-page-title-main">Gallium(III) bromide</span> Chemical compound

Gallium(III) bromide (GaBr3) is a chemical compound, and one of four gallium trihalides.

Tin(II) bromide is a chemical compound of tin and bromine with a chemical formula of SnBr2. Tin is in the +2 oxidation state. The stability of tin compounds in this oxidation state is attributed to the inert pair effect.

Bromine compounds are compounds containing the element bromine (Br). These compounds usually form the -1, +1, +3 and +5 oxidation states. Bromine is intermediate in reactivity between chlorine and iodine, and is one of the most reactive elements. Bond energies to bromine tend to be lower than those to chlorine but higher than those to iodine, and bromine is a weaker oxidising agent than chlorine but a stronger one than iodine. This can be seen from the standard electrode potentials of the X2/X couples (F, +2.866 V; Cl, +1.395 V; Br, +1.087 V; I, +0.615 V; At, approximately +0.3 V). Bromination often leads to higher oxidation states than iodination but lower or equal oxidation states to chlorination. Bromine tends to react with compounds including M–M, M–H, or M–C bonds to form M–Br bonds.

There are three sets of Indium halides, the trihalides, the monohalides, and several intermediate halides. In the monohalides the oxidation state of indium is +1 and their proper names are indium(I) fluoride, indium(I) chloride, indium(I) bromide and indium(I) iodide.

<span class="mw-page-title-main">Chromium(III) sulfate</span> Chemical compound

Chromium(III) sulfate usually refers to the inorganic compounds with the formula Cr2(SO4)3.x(H2O), where x can range from 0 to 18. Additionally, ill-defined but commercially important "basic chromium sulfates" are known. These salts are usually either violet or green solids that are soluble in water. It is commonly used in tanning leather.

<span class="mw-page-title-main">Beryllium bromide</span> Chemical compound

Beryllium bromide is the chemical compound with the formula BeBr2. It is very hygroscopic and dissolves well in water. The compound is a polymer with tetrahedral coordinated Be centres.

<span class="mw-page-title-main">Chromium(II) sulfate</span> Chemical compound

Chromium(II) sulfate refers to inorganic compounds with the chemical formula CrSO4·n H2O. Several closely related hydrated salts are known. The pentahydrate is a blue solid that dissolves readily in water. Solutions of chromium(II) are easily oxidized by air to Cr(III) species. Solutions of Cr(II) are used as specialized reducing agents of value in organic synthesis.

Chromium pentafluoride is the inorganic compound with the chemical formula CrF5. It is a red volatile solid that melts at 34 °C. It is the highest known chromium fluoride, since the hypothetical chromium hexafluoride has not yet been synthesized.

Titanium(III) bromide is the inorganic compound with the formula TiBr3. It is a blue black paramagnetic solid with a reddish reflection. It has few applications, although it is a catalyst for the polymerization of alkenes.

<span class="mw-page-title-main">Chromium(II) bromide</span> Chemical compound

Chromium(II) bromide is the inorganic compound with the chemical formula CrBr2. Like many metal dihalides, CrBr2 adopts the "cadmium iodide structure" motif, i.e., it features sheets of octahedral Cr(II) centers interconnected by bridging bromide ligands. It is a white solid that dissolves in water to give blue solutions that are readily oxidized by air.

<span class="mw-page-title-main">Chromium(III) phosphate</span> Chemical compound

Chromium(III) phosphate describes inorganic compounds with the chemical formula CrPO4·(H2O)n, where n = 0, 4, or 6. All are deeply colored solids. Anhydrous CrPO4 is green. The hexahydrate CrPO4·6H2O is violet.

<span class="mw-page-title-main">Iridium(III) bromide</span> Chemical compound

Iridium(III) bromide is a bromide of iridium(III), with the chemical formula of IrBr3.

References

  1. 1 2 3 4 5 Brauer, Georg (1965) [1962]. Handbuch Der Präparativen Anorganischen Chemie [Handbook of Preparative Inorganic Chemistry] (in German). Vol. 2. Stuttgart; New York, New York: Ferdinand Enke Verlag; Academic Press, Inc. p. 1340. ISBN   978-0-32316129-9 . Retrieved 2014-01-10.
  2. 1 2 3 4 Perry, Dale L. (2011). Handbook of Inorganic Compounds, Second Edition. Boca Raton, Florida: CRC Press. p. 122. ISBN   978-1-43981462-8 . Retrieved 2014-01-10.
  3. 1 2 3 NIOSH Pocket Guide to Chemical Hazards. "#0141". National Institute for Occupational Safety and Health (NIOSH).