The reaction of one mol of bromine with ethyne yields:
Halogens, especially chlorine and bromine on reaction with alkynes readily produces tetra-halogen derivatives of alkane. The reaction is carried out in inert solvent like carbon tetrachloride.
Due to the presence of two n-bonds, each molecule of the alkyne can react with two molecules of the halogen.
One mole of Bromine with ethyne gives 1,2-dibromoethene.
HC≡CH+Br2CCl4−−−→H(Br)C=C(Br)H