4-Iodobenzoic acid4-Iodobenzoic acid, or p-iodobenzoic acid, is an isomer of iodobenzoic acid.StructureX-ray crystallography of 4-iodobenzoic acid has shown that it crystallizes in the solid state as hydrogen-bonded dimers which stack perpendicular to their aromatic rings. The iodine atoms of adjacent dimers are also oriented towards each other due to van der Waals forces.Preparation4-Iodobenzoic acid may be prepared in the laboratory by the oxidation of p-iodotoluene with potassium permanganate.ReactionsThe carboxylic acid functionality of 4-iodobenzoic acid undergoes Fischer–Speier esterification with methanol to form the ester methyl 4-iodobenzoate.