Copper(I) bromide
| Copper(I) bromide | |
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-bromide-sample.jpg) |
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Other names
Cuprous bromide |
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| Identifiers | |
| CAS number | 7787-70-4  |
| PubChem | 24593 |
| ChemSpider | 22995 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | CuBr |
| Molar mass | 143.45 g/mol |
| Appearance | green powder (see text) |
| Density | 4.71 g/cm3, solid |
| Melting point |
492 °C, 765 K, 918 °F |
| Boiling point |
1345 °C, 1618 K, 2453 °F |
| Solubility in water | slightly soluble |
| Solubility | soluble in HCl, HBr, ammonium hydroxide negligible in acetone, sulfuric acid |
| Refractive index (nD) | 2.116 |
| Hazards | |
| EU Index | Not listed |
| Flash point | Non-flammable |
| Related compounds | |
| Other anions | Copper(I) chloride Copper(I) iodide |
| Other cations | Silver(I) bromide Copper(II) bromide Mercury(I) bromide |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Copper(I) bromide is the chemical compound with the formula CuBr. This diamagnetic solid adopts a polymeric structure akin to that for zinc sulfide. The compound is widely used in the synthesis of organic compounds.
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[edit] Preparation, basic properties, structure
The pure solid is colourless, although samples are often colored due to the presence of copper(II) impurities (see picture).[1] The copper(I) ion also oxidizes easily in air. It is commonly prepared by the reduction of cupric salts with sulfite in the presence of bromide.[2] For example, the reduction of copper(II) bromide with sulfite yields copper(I) bromide and hydrogen bromide:
- 2 CuBr2 + H2O + SO32− → 2 CuBr + SO42− + 2 HBr
CuBr is insoluble in most solvents due to its polymeric structure, which features four-coordinated, tetrahedral Cu centers interconnected by bromide ligands (ZnS structure). Upon treatment with Lewis bases, CuBr converts to molecular adducts. For example with dimethyl sulfide, the colorless complex is formed:[3]
- CuBr + S(CH3)2 → CuBr(S(CH3)2)
In this coordination complex, the copper is two-coordinate, with a linear geometry. Other soft ligands afford related complexes. For example triphenylphosphine gives CuBr(P(C6H5)3), although this species has a more complex structure.
[edit] Applications in organic chemistry
In the Sandmeyer reaction, CuBr is employed to convert diazonium salts into the corresponding aryl bromides:[2]
- ArN2+ + CuBr → ArBr + N2 + Cu+
The aforementioned complex CuBr(S(CH3)2) is widely used to generate organocopper reagents.[3] Related CuBr complexes are catalysts for Atom Transfer Radical Polymerization and Cu-catalyzed Cross-Dehydrogenative Couplings (CDC).
[edit] References
- ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ a b This report gives a procedure for generating CuBr: Jonathan L. Hartwell (1955), "o-Chlorobromobenzene", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv3p0185; Coll. Vol. 3: 185.
- ^ a b Jarowicki, K.; Kocienski, P. J.; Qun, L. "1,2-Metallate Rearrangement: (Z)-4-(2-Propenyl)-3-Octen-1-ol" Organic Syntheses, Collected Volume 10, p.662 (2004).http://www.orgsyn.org/orgsyn/pdfs/V79P0011.pdf
[edit] External links
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