It is formed by the condensation of acetylene tetrabromide with benzene in the presence of aluminium chloride: Br CH Br CH C H +C6H6=4HBr+C6H4) I, )C6H4, Br CH Br CH and similarly from methylene dibromide and benzene, and also when benzyl chloride is heated with aluminium chloride to 200° C. By condensing ortho-brombenzyl bromide with sodium, C. L.
Titanium tetrabromide, TiBr 4, is an amber-coloured crystalline mass.
Acetylene tetrabromide, C 2 H 2 Br 4, which is very conveniently prepared by passing acetylene into cooled bromine, has a density of 3 ooi at 6° C. It is highly convenient, since it is colourless, odourless, very stable and easily mobile.
The tetrabromide similarly gives TeOBr2.2S03 (W.
Soc., 1907, 91, p. 1849), by determining the ratio of tellurium dioxide to oxygen and by analysis of tellurium tetrabromide, obtained 127.60, and V.