Carbonyl bromide, also known as bromophosgene, is a
carbon oxohalide
Carbon () is a chemical element; it has symbol C and atomic number 6. It is nonmetallic and tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 electrons. It belongs to group ...
and a
bromine
Bromine is a chemical element; it has chemical symbol, 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 th ...
analogue of
phosgene
Phosgene is an organic chemical compound with the formula . It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. It can be thought of chemically as the double acyl chloride analog of ...
, with the
chemical formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
. It is a colorless liquid. Carbonyl bromide is a decomposition product of
halon Halon may refer to:
* Haloalkane, or halogenoalkane, a group of chemical compounds consisting of alkanes with linked halogens (in particular, bromine-containing haloalkanes)
* Halomethane compounds:
** Halon 10001 (iodomethane)
** Halon 1001 (bromo ...
compounds used in
fire extinguishers
A fire extinguisher is a handheld active fire protection device usually filled with a dry or wet chemical used to extinguish or control small fires, often in emergencies. It is not intended for use on an out-of-control fire, such as one which h ...
.
Synthesis and reactions
Carbonyl bromide is formed by the oxidation of
carbon tetrabromide with
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
:
:
In contrast to phosgene, carbonyl bromide cannot be produced efficiently by halogenation of
carbon monoxide
Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...
. The bromination of carbon monoxide follows this equation:
:
But the process is slow at room temperature. Increasing temperature, in order to increase the reaction rate, results in a further shift of the
chemical equilibrium
In a chemical reaction, chemical equilibrium is the state in which both the Reagent, reactants and Product (chemistry), products are present in concentrations which have no further tendency to change with time, so that there is no observable chan ...
towards the educts (since Δ
RH < 0 and Δ
RS < 0).
Carbonyl bromide slowly decomposes to carbon monoxide and elemental bromine even at low temperatures.
[
] It is also sensitive to
hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
, breaking down into
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 ...
and
carbon dioxide
Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
.
References
{{Reflist
Carbonyl compounds
Oxobromides
Carbon oxohalides