Iodobenzene

Iodobenzene is an organic compound consisting of a benzene ring substitituted with one iodine atom. It is a useful as a synthetic intermediate in organic chemistry. Since the C-I bond is weaker than C-Br or C-Cl, it is more reactive than bromobenzene or chlorobenzene. Iodobenzene can react with magnesium to form a Grignard reagent, phenylmagnesium iodide. Phenylmagnesium iodide, like the bromide analog, is a synthetic equivalent for the phenyl synthon. It can also serve as a substrate for the Sonogashira coupling, reacting it with an alkyne.

Preparation
Iodobenzene is commercially available, but it may be prepared in the laboratory from aniline. In the first step, the amine functional group is diazotized with hydrochloric acid and sodium nitrite. Potassium iodide is added to the resultant diazonium chloride, causing nitrogen gas to evolve. Any excess nitrite is hydrolyzed with a strong base; the mixture is acidified and the desired product is separated by steam distillation.

Alternatively, it may be produced by refluxing iodine and nitric acid with benzene.