Triiodoacetic acid
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| IUPAC name
2,2,2-triiodoacetic acid[1]
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Other names
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3D model (JSmol)
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| CI3COOH | |
| Molar mass | 437.741 g·mol−1 |
| Appearance | Yellow crystalline solid[2] |
| Density | 3.884±0.06 g/cm3 (predicted)[2] |
| Melting point | 135–140 °C (275–284 °F; 408–413 K)[2] |
| Boiling point | 347.7±42.0 °C (predicted)[2] |
| Insoluble[3] | |
| Solubility | Slightly soluble in chloroform, ethyl acetate, methanol. Sparingly soluble in DMSO. |
| Acidity (pKa) | 1.29±0.41 (predicted)[2] |
Refractive index (nD)
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1.883 (predicted)[4] |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards
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Highly toxic |
| GHS labelling: | |
| Danger | |
| H301, H314 | |
| P280, P301+P310, P305+P351+P338, P310 | |
| Related compounds | |
Related compounds
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
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Triiodoacetic acid is an organic compound with the chemical formula CI3COOH. It is a yellow solid. It is one of the haloacetic acids.
Synthesis
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.
- 5 CH2(COOH)2 + 6 I2 + 3 HIO3 → 5 CI3COOH + 5 CO2 + 9 H2O
It can also be prepared by reacting diiodomalonic acid and a suspension of iodine in aqueous iodic acid, with a 30 % yield.
- 5 CI2(COOH)2 + 2 I2 + HIO3 → 5 CI3COOH + 5 CO2 + 3 H2O
Diiodomalonic acid itself is prepared by reaction of malonic acid with iodine and iodic acid in formic acid as a solvent.[3]
Properties
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.[3]
References
- ^ a b PubChem. "Triiodoacetic acid". pubchem.ncbi.nlm.nih.gov. Retrieved 2026-03-14.
- ^ a b c d e Chemical Book. "TRIIODOACETIC ACID". www.chemicalbook.com. Retrieved 2026-03-14.
- ^ a b c Cobb, R (September 1958). "Notes: Synthesis and Properties of Triiodoacetic Acid and Its Salts". The Journal of Organic Chemistry. 23 (9): 1368–1405. doi:10.1021/jo01103a038.
- ^ ChemSpider. "Triiodoacetic acid". www.chemspider.com. Retrieved 2026-03-14.