Carminic acid

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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.

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.

References

  1. https://link.springer.com/article/10.1007/s10953-012-9830-7

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