Carminic acid
| Names | |
|---|---|
| IUPAC name
3,5,6,8-Tetrahydroxy-1-methyl-9,10-dioxo-7-[(2S,3R,4R,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]-9,10-dihydroanthracene-2-carboxylic acid
| |
| Other names
7-Glucopyranosyl-3,5,6,8-tetrahydroxyl-1-methyl-9,10-dioxoanthracene-2-carboxylic acid
C.I. 75470 CI 75470 Natural Red 4 | |
| Properties | |
| C22H20O13 | |
| Molar mass | 492.38 g/mol |
| Appearance | Dark red or purple-red solid |
| Melting point | 120–136 °C (248–277 °F; 393–409 K) (decomposes) |
| Boiling point | Decomposition |
| 0.13 g/100 ml (25 °C) | |
| Solubility | Soluble in methanol, conc. sulfuric acid Slightly soluble in diethyl ether Practically insoluble in benzene, chloroform, petroleum ether, toluene |
| Vapor pressure | ~0 mmHg |
| Acidity (pKa) | 3.39, 5.78, 8.35, 10.27, 11.51[1] |
| Hazards | |
| Safety data sheet | Sigma-Aldrich |
| Related compounds | |
| Related compounds
|
Carmine |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Carminic acid (C22H20O13) is a red glucosidal hydroxyanthrapurin that occurs naturally in some scale insects, such as the cochineal, Armenian cochineal, and Polish cochineal, which the insects produce as a deterrent to predators. An aluminum salt of carminic acid is the coloring agent in carmine, a pigment.
Contents
Properties
Chemical
Carminic acid turns dark when heated close to its decomposition point.
Physical
Carminic acid is a dark red powder, though its shade varies on multiple factors. Aqueous solutions are deep red in color, while acidic solutions tend to be yellow or violet. It is only slightly soluble in cold water, and a bit more soluble in hot water.
Availability
Carminic acid can be extracted from the female members of the scale insects, such as the cochineal, Armenian cochineal, and Polish cochineal. The crushed product is purified by removing the insect bits, and washed.
Lastly it can be bought from chemical suppliers.
Preparation
Synthesis of this compound is complicated and expensive, and it's just cheaper to extract it from insects. However, this requires one to know how to grow and harvest the cochineal insects first, before doing any chemical extraction.
Projects
- Make carmine
- Food coloring and pigment
- Orth′s lithium carmine technique for nuclear staining
- Test for glycogen
Handling
Safety
Carminic acid displays little toxicity, but it may irritate the eyes or nose if exposed. May cause allergy in people with chronic inducible urticaria.
Storage
Carminic acid should be kept in airtight bottles, away from light and oxidizers.
Disposal
No special disposal is required. Can be diluted and poured down the drain, or dumped in the ground.
