149-150 A.] 



PURPURIN 



241 



Gaulthier de Claubry and Persoz, Ann. 

 Chim. [2] 48, 69; 51, no; Runge, 

 Ibid. 63, 282; Schiel, Ann. 60, 74; 

 Debus, Ann. 66, 351 ; 86, 117 ; Wolff 

 and Strecker, Ann. 75, I ; Rochleder, 

 Ann. 80, 321 ; 82, 205 ; Stenhouse, 

 Proc. Roy. Soc. 12, 633; 13, 145; 

 Kopp, Jahresber. 1861, 938 ; Schiitzen- 

 berger, Bull. Soc. [2] 4, 12; Jahresber. 

 1864, 542; Auerbach, Ber. 4, 979; 

 Schiinck and Romer, Ber. 10, 551)- 



The carboxylic acid also occurs in 

 madder (Schiitzenberger and Schiffert, 

 Bull. Soc. [2] 4 ; 13; Rosenstiehl, Comp. 

 Rend. 84, 561 ; Liebermann, Ber. 1O, 

 1618). 



SYNTHETICAL PROCESSES. 



[A.] From phenol [60] and pktkalic 

 anhydride [54; R,]. The phenol is 

 converted into p-chlorphenol (see under 

 resorcinol [70; C]), and this, when 

 heated with phthalic anhydride and 

 strong sulphuric acid, gives (with 

 i : 4-dihydroxyanthraquinone) a small 

 quantity of purpurin (Liebermann and 

 Giesel, Ber. 10, 608). The i : 4-di- 

 hydroxy-quinone (quinizarin) yields 

 purpurin on oxidation with sulphuric 

 acid and manganese dioxide (Baeyer 

 and Caro, Ber. 8, 152). 



[B.] Prom quinol [7l] and phthalic 

 anhydride through quinizarin by heat- 

 ing a mixture of these two compounds 

 with strong sulphuric acid (Grimm, 

 Ber. 6, 506 ; Liebermann, Ann. 212, 11), 

 and then as above under A. 



[C.] From alizarin [145] by oxida- 

 tion with manganese dioxide and sul- 

 phuric acid (De Lalande, Comp. Rend. 

 79, 669; Ber. 7, 1545; Jahresber. 

 1874, 486). Or by heating with strong 

 sulphuric acid to 225 (Liebermann and 

 Hohenemser, Ber. 35, 1781). 



Or alizarin on nitration of the di- 

 acetate gives a-nitro- = 4-nitroalizarin 

 (Perkin, Ber. 8, 780; Journ. Ch. Soc. 

 1876, 2, 578; Jahresber. 1877, 587; 

 Schunck and Romer, Ber. 12, 587 ; 

 Brasch, Ber. 24, 1612), and this on 



reduction with sodium amalgam or 

 ammonium sulphide yields a-amino- 

 alizarin (Perkin, loc. cit. ; Brasch, loc. 

 cit.}. The latter gives purpurin by the 

 diazo-method (Brasch, loc. cit. 1614 : 

 see also Meister, Lucius, and Briining, 

 Germ. Pat. 97688 of 1897; Ch. Centr. 

 1898, 2, 696). 



[D.] From purpuroxanthin [146] by 

 fusion with caustic potash (Noah, Ber. 



!9, 333)- 



[E.] Anthraquinone [144; C] gives 

 purpurin by brominating to a-dibrom- 

 and finally to tribromanthraquinone 

 (Graebe and Liebermann, Ann. Suppl. 

 7, 289; Diehl, Ber. 11, 181). The 

 latter yields purpurin on fusion with 

 potash at 200 (Diehl, loc. cit. 184). 



150. Methylpurpuroxaiithiii ; 



1 : 3-Diliydroxy-G-Metliylanthra- 



quinone. 



HO 



NATURAL SOURCE. 



In the colouring-matter ' mang- 

 koudu ' from the root bark of Morinda 

 umbellata from Java and the Malay 

 Peninsula, and from E., S., and S. W. 

 India (A. G. Perkin and Hummel, 

 Trans. Ch. Soc. 65, 863). 



SYNTHETICAL PROCESS. 



[A.] From benzole acid [Vol. II] 

 through 3 : 5-dihydroxybenzoic acid (see 

 under purpuroxanthin [146 ; A]) and 

 toluene [54; A, &c.] through p-toluic 

 acid (see under o-cresol [61 ; A]). 

 A mixture of the two acids gives 

 methylpurpuroxanthin on heating with 

 strong sulphuric acid (Marchlewski, 

 Trans. Ch. Soc. 63, 1142). 



