Used as a synthetic intermediate for pharmaceuticals radiopharmaceuticals (iodine-131 labeling) and as a probe in biochemical studies of thyroid hormone analogs and enzyme inhibitors.

Serves as a scaffold for medicinal chemistry leveraging the iodine for radioiodination and the phenoliccarboxylic acid groups for hydrogen bonding interactions in drug design.

4-Hydroxy-3-iodobenzoic acid (CHIO MW 264.02 gmol) is a halogenated benzoic acid derivative featuring a phenolic hydroxyl group ortho to iodine and para to the carboxylic acid typically appearing as a white to off-white crystalline powder.