Copper (I) bromide

Crystal structure
__ Cu +      __ Br -
General
Surname	Copper (I) bromide
Ratio formula	CuBr
Brief description	pure white crystals
External identifiers / databases
CAS number 7787-70-4 EC number 232-131-6 ECHA InfoCard 100.029.210 PubChem 24593 Wikidata Q417906
properties
Molar mass	143.45 g mol −1
Physical state	firmly
density	4.98 g cm −3
Melting point	492 ° C
boiling point	1345 ° C
solubility	poorly soluble in water
Refractive index	2.117
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 315-319-335 P: 261-305 + 351 + 338
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Copper (I) bromide is a copper salt of hydrogen bromide with the ratio formula CuBr. Copper has the +1 oxidation state .

presentation

Copper (I) bromide can be produced by the reaction of elemental copper with hydrobromic acid. For this purpose, elemental copper is reacted with an ethereal solution of HBr and the resulting HCuBr _{2 is} decomposed with water

${\displaystyle \mathrm {2\ Cu\ +2\ HBr\longrightarrow \ 2\ CuBr\ +H_{2}} }$

Another possible synthesis is the reduction of copper (II) bromide . Sulfite compounds , for example, can serve as reducing agents .

${\displaystyle \mathrm {2\ CuBr_{2}\ +\ SO_{3}^{2-}\ +\ H_{2}O\longrightarrow } }$ ${\displaystyle \mathrm {2\ CuBr\ +SO_{4}^{2-}+2\ HBr} }$

This reduction can also take place when the copper (II) bromide is boiled in acidic solution with an excess of copper.

${\displaystyle \mathrm {CuBr_{2}\ +\ Cu\longrightarrow } }$ ${\displaystyle \mathrm {2\ CuBr} }$

Synthesis by reaction of copper sulfate pentahydrate with potassium bromide and sulfur dioxide is also possible .

${\displaystyle \mathrm {2\ CuSO_{4}\cdot 5H_{2}O+2\ KBr+SO_{2}+2\ H_{2}O\longrightarrow 2\ CuBr+2\ H_{2}SO_{4}+K_{2}SO_{4}} }$

properties

The actual salt is colorless. It gets its greenish color from impurities of copper (II) ions. Copper (I) bromide is insoluble in most solvents . It is sparingly soluble in water, but soluble in hydrohalic acids, nitric acid and aqueous ammonia . Copper (I) bromide occurs in three modifications. Below 391 ° C it is present as γ-CuBr with a crystal structure of the zinc blende type and the space group F 4 3 m (space group no. 216) (a = 5.691 Å). β-CuBr with a crystal structure of the wurtzite type is between 391 ° C and 470 ° C. α-CuBr with a cubic crystal structure above 470 ° C.

• 

  Copper (I) bromide

• 

  Copper (I) bromide (oxidized)

use

One area of ​​application for copper (I) bromide is the Sandmeyer reaction . Here it is used as a catalyst for the synthesis of aryl bromides from aryl amines via the corresponding diazonium salts . When thermally excited, gaseous copper (I) bromide generates blue light, which has a higher color saturation than the light emitted by copper (I) chloride . Copper (I) bromide is therefore a suitable emitter for pyrotechnic flares.

literature

• Wiberg, E .; Wiberg, N .; Holleman, AF : Inorganische Chemie , 103rd edition, 2017 Walter de Gruyter GmbH & Co. KG, Berlin / Boston, ISBN 978-3-11-026932-1 , p. 1696.

Individual evidence

1. ↑ ^{a b c d} Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 974.
2. ↑ ^{a b c} data sheet copper (I) bromide from AlfaAesar, accessed on February 3, 2010 ( PDF )(JavaScript required) . .
3. ↑ ^{a b c d e} Yoffe, D .; Frim, R .; Ukeles, SD; Dagani, MJ; Barda, HJ; Benya, TJ; Sanders, DC: Bromine Compounds. In: Ullmanns Enzyklopädie der Technischen Chemie , Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2013; doi : 10.1002 / 14356007.a04_405.pub2 .
4. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Index of Refraction of Inorganic Crystals, pp. 10-246.
5. ↑ ^{a b} Data sheet Copper (I) bromide from Sigma-Aldrich , accessed on April 7, 2011 ( PDF ).
6. ↑ Hollemann Wieberg: Textbook of Inorganic Chemistry . 91-100 Edition. Walter de Gruyter, Berlin New York 1985, ISBN 3-11-007511-3 , pp. 1003 .
7. ↑ E.-C. Koch: Spectral Investigation and Color Properties of Copper (I) Halides CuX (X = F, Cl, Br, I) in Pyrotechnic Combustion Flames , Propellants, Explos. Pyrotech. 2015, 40 , 799-802. doi : 10.1002 / prep.201500231 .