The Iodination of Aromatic Compounds. IV. The Iodination of Aromatic Hydrocarbons and Nuclear-substituted Phenols

Abstract

Salicylic acid and p-nitrophenol are almost quantitatively diiodinated when treated in alcoholic solution with iodine, hydrogen peroxide, and sulphuric, nitric, hydrochloric, or phosphoric acid. In glacial acetic acid solution salicylic acid gives good yields of the diiodo compound only in the presence of hydrochloric acid. No appreciable iodination occurs in the presence of sulphuric or nitric acid whilst 3,5-dibromosalicylic acid is formed with hydrobromic acid. Cinnamic acid reacts slowly with iodine, hydrogen peroxide, and sulphuric acid in methanol and ethanol solutions to give the corresponding α-iodo-β-alkoxy-β-phenylpropionic acids. Benzene homologues are readily iodinated in alcoholic solution in the presence of sulphuric or nitric acid although benzene does not react appreciably under similar conditions.