Copper(II) bromide ( Cu Br₂) is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

. It is used in

photographic processing Photographic processing or photographic development is the chemical means by which photographic film or paper is treated after photographic exposure to produce a negative or positive image. Photographic processing transforms the latent image in ...

as an intensifier and as a brominating agent in organic synthesis. It is also used in the

copper vapor laser Copper vapor laser (CVL) uses vapors of copper as the lasing medium in a 4-level laser. It produces green laser light at 510.6 nm and yellow laser light at 578.2 nm. The pulse width is typically from 5 to 60 ns, and peak power from 50 ...

, a class of laser where the medium is copper bromide vapour formed in-situ from

hydrogen bromide Hydrogen bromide is the inorganic compound with the formula . 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 tempe ...

reacting with the copper discharge tube. Producing yellow or green light, it is used in

dermatological Dermatology is the branch of medicine dealing with the skin.''Random House Webster's Unabridged Dictionary.'' Random House, Inc. 2001. Page 537. . It is a speciality with both medical and surgical aspects. A dermatologist is a specialist medical ...

applications.

Synthesis

Copper(II) bromide can be obtained by combining copper oxide and hydrobromic acid: :CuO + 2HBr → CuBr₂ + H₂O.

Purification

Copper(II) bromide is purified by crystallization twice from water, filtration to remove any CuBr and concentration under vacuum. This product is dehydrated using phosphorus pentoxide.

Molecular and crystal structure

In the solid state CuBr₂ has a polymeric structure, with CuBr₄ planar units connected on opposite sides to form chains. The crystal structure is

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...

C2/m, with lattice constants a = 714 pm, b = 346 pm, c = 718 pm, e ß = 121° 15'. CuBr₂ monomeric units are present in the gas phase at high temperature. It forms bright green-blue solutions in water, and reacts with Aluminium exothermically: 3 CuBr₂ + 2 Al forms 2 AlBr₃ and 3 Cu.

Reactions

Copper (II) bromide in chloroform-ethyl acetate reacts with ketones resulting in the formation of alpha-bromo ketones. The resulting product can be directly used for the preparation of derivatives. This heterogeneous method is reported to be the most selective and direct method of formation of α-bromo ketones. Dibromination of NPGs, n-pentenyl glycosides, using CuBr₂/LiBr reagent combination was performed in order for an NPG to serve as a glycosyl acceptor during halonium-promoted couplings. Such reaction gives high yield of the dibromides from alkenyl sugars that are resistant to a direct reaction with molecular bromine.

Usage

Copper(II) bromide lasers produce pulsed yellow and green light and have been studied as a possible treatment for cutaneous lesions. Experiments have also shown copper bromide treatment to be beneficial for skin rejuvenation. It has been widely used in photography as its solution was used as the bleaching step for intensifying collodion and gelatin negatives. Copper(II)bromide has also been proposed as a possible material in humidity indicator cards.

Safety

Copper(II) bromide is harmful if swallowed. It affects the central nervous system, brain, eyes, liver, and kidneys. It causes irritation to skin, eyes, and respiratory tract.

Natural occurrence

Pure copper(II) bromide is as yet (2020) unknown among minerals. However, barlowite, Cu₄BrF(OH)₆, is worth of mention.

References

{{bromine compounds Bromides Metal halides Copper(II) compounds