Triiodoacetic acid is an organic compound with the chemical formula . It is a yellow solid. It is one of the haloacetic acids.
Triiodoacetic acid can be synthesized in good yields by reacting malonic acid, iodine and aqueous iodic acid, but triiodoacetic acid is contaminated with large amounts of unreacted iodine, and because of that it looks dark brown. If iodic to malonic acid ratio is 1.5 by weight, triiodoacetic acid as a major product (50-60 %) can be obtained.
It can also be prepared by reacting diiodomalonic acid and a suspension of iodine in aqueous iodic acid, with a 30 % yield.
Diiodomalonic acid itself is prepared by reaction of malonic acid with iodine and iodic acid in formic acid as a solvent.
Triiodoacetic acid is a yellow crystalline solid, but can be dark brown due to impurities of iodine. Crystalline triiodoacetic acid is quite stable at room temperature, but decomposes rapidly at higher temperatures to iodine, iodoform and carbon dioxide. It is very soluble in polar organic solvents, but the solutions are extremely unstable, rapidly getting iodine discoloration. It is insoluble in water, but its aueous suspensions are quite stable. It is soluble in dilute (4 %) aqueous NaOH, but decomposes rapidly. In more concentrated NaOH it is insoluble, with little decomposition.
The lead and sodium salts of triiodoacetic acid were isolated in 1958, but attempts to isolate the calcium salt were unsuccessful.