Rhubarb, Frangula-Emodin Methyl Ether(CHAPTER I. The Anthraquinone 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.

FRANGULA-EMODIN METHYL ETHER.

This compound, as already stated, is found associated with crude chrysophanic acid, and to its contamination with this impurity is to be ascribed the lower melting-point at first assigned to this latter substance. Originally isolated by Perkin and Hummel (Trans. Chem. Soc., 1894, 65,632) from the root- bark of the Ventilago madraspatana and by Perkin from the root of the Polygonum cuspidatum (ibid., 67, 1084), it was identified by Tutin and Clewer (ibid., 1910, 97, 1) as one of the constituents of the Rumex ecklonianus. Jowett and Potter (ibid., 1903, 77, 1330) who prepared this compound by the methylation of emodin doubted at first the identity of their product with the natural compound, but somewhat later Tutin and Clewer (loc. cit.) proved this to be the case.

It can be isolated (Oesterle and Johann, Arch. Pharm., 1910, 248, 476) by extracting the acetylated crude chrysophanic acid with alcohol at 50-55°, and hydrolysing the acetylemodin methyl ether thus produced, and has also been obtained (Tutin and Clewer) by a fractional extraction of the constituents of rhubarb root. The properties of this compound, which crystallises in orange-red needles, are described later in connection with the root-bark of the Ventilago madraspatana.

According to Oesterle and Johann this emodin methyl ether is identical with Gilson's rheo-chrysidin (Arch, internat. Pharm. Ther., 1905, 14, 492), with Hesse's physcion (lichen-chrysophanic acid) (Abst., 1906, 1, 280), and with the methyl-chrysophanic acid of this latter author (Abst., 1900, 1, 41).