C.I. Natural Red 4
3D model (JSmol)
|E number||E120 (colours)|
|Molar mass||492.38 g/mol|
|Melting point||120 °C (248 °F; 393 K) (decomposes)|
|Acidity (pKa)||3.39, 5.78, 8.35, 10.27, 11.51|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Carminic acid (C22H20O13) is a red glucosidal hydroxyanthrapurin that occurs naturally in some scale insects, such as the cochineal, Armenian cochineal, and Polish cochineal. The insects produce the acid as a deterrent to predators. An aluminum salt of carminic acid is the coloring agent in carmine. Synonyms are C.I. 75470 and C.I. Natural Red 4.
The chemical structure of carminic acid consists of a core anthraquinone structure linked to a glucose sugar unit. Carminic acid was first synthesized in the laboratory by organic chemists in 1991.
- Merck Index, 11th Edition, 1850.
- Atabey, Hasan; Sari, Hayati; Al-Obaidi, Faisal N. (28 April 2012). "Protonation Equilibria of Carminic Acid and Stability Constants of Its Complexes with Some Divalent Metal Ions in Aqueous Solution". Journal of Solution Chemistry. 41 (5): 793–803. doi:10.1007/s10953-012-9830-7.
- Allevi, P.; et al. (1991). "The First Total Synthesis of Carminic Acid". Journal of the Chemical Society-Chemical Communications. 18: 1319–1320. doi:10.1039/C39910001319.