PERKIN AND ALLISON : RHAMNAZIN AND RHAMNETIN. 469

X LVII. -!hamnu xin and Rharnne tin.

By ARTHUR GEORGE PERKIN, F.R.S.E., and JOHN RAYMOND ALLISON, B.Sc.

ALTHOUGH rharnnetin has been shown to be a monomethyl ether of quercetin (Herzig, Morzatsh., 1888, 9, 548), the locality of the methoxyl group has hitherto not been definitely ascertained, and either the (3) or the 7-position might equally well be assigned to it. Similarly, in rhamnazin (Trans., 1897, 71, SlS), a quercetin dimethyl ether although the position of one methoxyl group is known, that of the

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4 70 PERKIN AND ALLISON : RHAMNAZIN AND RHAMNETIN.

second, as in the case of rhamnetin, is uncertain. Thus if rhamnetin or rhamnazin be decomposed by digestion with boiling alcoholic potash or by the aspiration of air through its alkaline solution, protocatechuic acid and vanillic acid respectively are produced besides a syrupy phloroglucinol derivative; the yield of the latter, however, is small, and being readily soluble it is difficult to identify; moreover, preparation of the raw material, especially rhamnazin, is extremely laborious. For the phenols in question, three constitutions were possible, namely, tha t of phloroglucinol monomethyl ether, or those of the hydroxpfisetol monomethyl ethers,

OMe/\OH O H A O I E 1 bO*CH,*OH and I ICO*CH,*OMe ; \/

O H \/

OH

these two being suggested by Herzig's (Monatsh., 1891, 12, 187) de- composition of fisetin tetramethyl ether into fisetol and veratric acid.

The study of the azobenzene derivatives of phloroglucinol (Traqs., 1897, 71, 189, 1154) and other compounds derived from it, has shown that such substances are sparingly soluble and readily crystallised, and it appeared likely that the phenols from rhamnetin and rhamnazin might be identified by these means.

Rhamnaxirt was decomposed by digestion for several days with boil- ing alcoholic potash, but this is more rapidly accomplished (in about two hours) by the aspiration of air through its solution in dilute aqueous potassium hydroxide. The phenolic product of the reaction which is the same in both cases, was isolated in the usual manner, and its solution in dilute sodium carbonate treated with diazobenzene sulphate until a precipitate no longer formed ; this, which is orange- red, was collected, well washed, transferred to a dish, and dried on the water-bath. Extraction with alcohol removed a resinous compound, and the residue, after being crystallised two or three times from a mixture of alcohol and acetic acid, gave an average yield of about ten per cent. of the rhamnazin employed :

0.0919 gave 0.2208 CO, and 0.0377 H,O. 0.0844 ,, 11.7 C.C. nitrogen at 16O and 754 mm. N = 16-02.

C = 65.51 ; H = 4.54.

(C6H5N2)2C,H30,*OCH3requires C = 65.51; H = 459; N = 16.09 per cent.

It formed glistening orange-red needles sparingly soluble in alcohol and melting at 250-2529

Rhamnetin was decomposed by the same methods, and the phenolic product converted into its disazobenzene derivative. This melted at 250-252O, and was identical with that obtained from rhamnazin :

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PERKIN AND ALLISON: RHAMNAZIN AND RHAMNETIN. 471

0.1136 gave 0-2715 CO, and 0.0475 H,O. 0.1157 ,, 15.6 C.C. nitrogen at 14O and 746 mm. N = 15.57.

C=65*17 ; H=4.64.

0.1788 ,$ 0.1234 AgI. OCH3=4*40. C,,H,,O,N,*OCH, requires C = 65.5 1 ; H = 4.59 ; N = 16.09 ; OCH, =

4.31 per cent.

This compound is therefore disaxobenxene phloroglucinol monomethpl ether, and the phenol obtained both from rhamnazin and from rham- netin is phloroglucinol monomethyl ether. The relationship of these colouring matters may, therefore, be indicated by the formulae,

0 OMe 0 OH

Rhamnazin. Rhamnetin.

and the suggestion (Zoc. cit.) that rhamnazin was rhamnetin mono- methyl ether is thus shown to be correct.

The shades given by these colouring matters upon mordanted wool are as follows :

Rhamnetin . . . . . . Red-brown. Brown-orange. Bright orange. Olive-black. Rhamnazin . . . . . . Golden-yellow. Orange-yellow. Lemon-yellow. Olive-brown.

These results show that the dyeing properties of rhamnetin are identicul with those of quercetin, and are interesting in that they prove that in quercetin the hydroxyl (7)” has no effect on its dyeing properties. On the other hand, the replacement of the hydroxyl (3’) by methoxyl with production of rhamnazin (compare also isorhamnetin, quercetin monomethyl ether [OMe = 3‘1 Trans., 1898, 73, 267) has a most marked effect on the dyeing properties ; this was to be expected, as the compound does not then possess o-hydroxyl groups. A third quercetin monomethyl ether has been shown to exist in minute quantity in the Tarnaris Africana (Trans., 1898,73, 380), and an attempt is now being made to obtain sufficient substaiice for the location of its methoxy-group in the above manner.

Quercetin Tetramethyl and Tetraethyl Ethers.-These compounds, as Herzig has shown (Monatsh., 1888, 9, 552), when decomposed with alco- holic potash, give respectively protocatechuic acid dimethyl and diethyl ether, and also phenolic compounds which are derivatives of phloroglucinol ; to determine the constitution of the latter, their azo-

Chromium. Aluminium. Tin. Iron.

0 OH

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4'72 PERKIN AND ALLISON : RHAMNAZIN AND RHAMNETIN.

benzene compounds were examined, with the result; that the one derived from quercetin tetramethyl ether was found to bo disaxo6enzene phloro- qlucinol monomethyl e t h ; m. p. 250-252"

The phenol from the tetraethyl ether gave a disaeobenzene compound crystallising in orange-red needles melting a t 212-214' :

0,0828 gave 0.2015 CO, and 0*0365 H,O. 0.0771 ,, 10.6 C.C. nitrogen at 18' and 751 mm. N = 15.53.

C = 66.36 ; H = 4-89.

(C,H,N,),C,H(OH),*OC,H5 requires C= 66.24 ; H = 4.94 ; N = 15.47 per cent.

It was evidently disaxobenxerze pltlorogZminoZ morzoethyl ether. Karnpherol Monomethyl Ether.-A trace of this substance, recently

described by Testoni (Galzzetta, 1900, 30, ii, 327) as a constituent of Galanga root (AZpinia oficinarum), was available for examination. When decomposed by the aspiration of air through its alkaline solution, it yielded benzoic acid, (m. p. 121"), and a phenolic compound which gave the phloroglucinol reaction. I n the presence of sodium carbonate, this give an azobenzene compound, identified as trisazobenzene phloro- glucinol, and consequently there was no methoxy-group in this portion of the molecule. Adopting the constitution for kampherol suggested by Kostanecki, it is evident that the above methyl ether must be re- presented as follows :

0

W v C ' O M e O H p p C - < - > I I - .

O H CO

This method of analysis has already been employed with the decom- position products of the ethers of luteolin (Trans., 1900, 77, 1314), myricetin (Trans., 1902, 81, 203), and genistein (Trans., 1900, 77, 1310), with the result that in all cases the ethers of phloroglucinol were isolated. There is no reason to doubt that the corresponding derivatives of chrysin and apigenin would by similar methods give a like result, and it appeared unnecessary to undertake their preparation for this purpose.

The authors are indebted to the Research Fund Committee of the Chemical Society for a grant which has been in part employed to cover the expense of this research.

CLOTHWORKERS' RESEARCH LABORATORY, DYEING DEPARTMENT,

YORESHIRE COLLEGE.

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