1,2-Dibromoethylene, also known as 1,2-dibromoethene and acetylene dibromide, is a dihalogenated unsaturated compound with one
bromine on each of the two
carbon atoms. There are two
isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
Iso ...
s of this compound,
''cis'' and ''trans''. Both isomers are colorless liquids.
Synthesis
1,2-Dibromoethylene can be synthesized by
halogenation
In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, ...
of
acetylene
Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
(CH) with bromine (Br). In order to prevent the formation tetrahalogenated compounds,
acetylene
Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
is used in excess, with Br as the
limiting reagent.
:
Alternately, halogenation of this kind could also be achieved through the use of two equivalents of
''N''-bromosuccinimide and
lithium bromide (LiBr). ''N''-Bromosuccinimide provides Br as an
electrophile, which is followed by Br from LiBr.
:
References
{{DEFAULTSORT:Dibromoethylene, 1, 2-
Bromoalkenes