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 ...

that forms an unstable tetrahydrate CuBr₂·4H₂O. 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 i ...

as an

intensifier In linguistics, an intensifier (abbreviated ) is a lexical category (but ''not'' a traditional part of speech) for a modifier that makes no contribution to the propositional meaning of a clause but serves to enhance and give additional emotional ...

and as a brominating agent in

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

. It is also used in the

copper vapor laser A 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 temper ...

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 medic ...

applications.

Synthesis

Copper(II) bromide can be obtained by combining copper oxide and hydrobromic acid: :CuO + 2HBr → CuBr₂ + H₂O. The tetrahydrate can be produced by recrystallization of solutions of copper(II) bromide at 0 °C. If heated above 18 °C, it releases water to produce the anhydrous form.

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 Phosphorus pentoxide is a chemical compound with molecular formula Phosphorus, P4Oxygen, O10 (with its common name derived from its empirical formula, P2O5). This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desic ...

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 Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...

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

C2/m, with

lattice constants A lattice constant or lattice parameter is one of the physical dimensions and angles that determine the geometry of the unit cells in a crystal lattice, and is proportional to the distance between atoms in the crystal. A simple cubic crystal has ...

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. The tetrahydrate, structurally formulated as uBr₂(H₂O)₂�2H₂O, has a monoclinic crystal structure and consists of distorted square planar''trans''- uBr₂(H₂O)₂centres as well as two molecules of

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

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 unknown among minerals. However, barlowite, Cu₄BrF(OH)₆, contains both copper and bromide.

References

{{Bromides Bromides Metal halides Copper(II) compounds