Coerule-ellagic Acid(CHAPTER XII. Diphenyl-Dimethylolid Group.)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Coeruleoellagic acid is prepared by heating ellagic or flavellagic acids (1 part) with sulphuric acid (monohydrate 10 parts) to 200° and allowing the temperature to fall to 185-190° and remain there for thirty minutes. The product isolated by pouring into water is purified by conversion into its acetyl derivative, and this is subquently hydrolysed by means of sulphuric acid in the presence of acetic acid. It may also be obtained by the oxidation of ellagic or flavellagic acids (1 part) in sulphuric acid solution (10 parts) with arsenic acid (1 part) at 100-130° (Perkin, Chem. Soc. Trans., 1916, 109, 529).

Coeruleoellagic acid, C₁₄H₆O₁₀, separates from hot pyridine in small pale yellow prismatic needles which melt above 360° and are very sparingly soluble in the usual solvents. Concentrated solutions of the alkali hydroxides dissolve it with a greenish-yellow colour, which on dilution become green and finally of a blue colour, and these changes appear to arise from oxidation. Sodium and potassium carbonate solutions also give blue liquids. On distillation with zincdust fluorene is produced.

Acetylcoeruleoellagic acid, C₁₄O₁₀(C₂H₃O)₆, colourless needles, melting-point 330-332°, and benzoylcoeruleoellagic acid, C₁₄O₁₀(C₇H₅O)₆, melting-point 343-345°, have been prepared. The latter is more sparingly soluble in benzoic anhydride than the corresponding derivative of flavellagic acid, and this property provides a means for the separation of the two substances.

By digestion with 50 per cent, potassium hydroxide solution diluted with its own volume of alcohol, coeruleoellagic acid gives a compound C₁₂H₁₀O₈, evidently octohydroxydiphenyl. This consists of an almost colourless crystalline powder, soluble in dilute potassium hydroxide solution, with a reddish-violet coloration which becomes brown on exposure to air. The acetyl derivative, C₁₂H₂O₈(C₂H₃O)₈, forms colourless needles melting at 177-178°.

The constitution assigned to coeruleoellagic acid is as follows: [KUVA PUUTTUU] a formula which represents it as either a dihydroxy-ellagic or hydroxy flavellagic acid.

Coeruleoellagic acid possesses well-marked dyeing properties of a similar character, though more strongly developed than those of ellagic and flavellagic acids, and may have practical utility. Owing to its sparing solubility it gives the best results in the paste form. The following results are obtained by the employment of mordanted woollen cloth:

Chromium.	Aluminium.	Tin.	Iron.
Deep olive-yellow.	Greenish-yellow.	Dull yellow.	Greenish-black.

In the case of the aluminium mordant the employment of chalk in the dye-bath exerts a detrimental effect.