332 CAROTENOIDS OF UNCERTAIN STRUCTURE XIV 



Solubility: Tonilarhodin is easily soluble in carbon disulphide, chloroform 

 and pyridine, less easily soluble in ether, benzene and hot ethanol, very sparingly 

 soluble in methanol and almost insoluble in petroleum ether. 



Solvent: Absorption maxima: 



Carbon disulphide 582 541 502 m/x 



Benzene 557 519 485 m/i 



Petrol 537 501 (467) m^ 



Pyridine 558 518 485 mpi 



Chloroform 554 515 (483) m/z 



Methanol 529 493 (460) m/i 



Ethanol 532 495 463 van 



The large difference in the location of the absorption maxima in carbon 

 disulphide and in petrol or ethanol, is remarkable. The differences in the 

 positions of the longest wavelength bands amount to 45-50 m//, whereas in 

 other carotenoids the differences are usually of the order of 30-40 m/i. 



Optical activity: No data have been recorded. 



Partition test: On partition between petroleum ether and 95 % methanol, 

 the two zones are about equally coloured. 



Chromatographic behaviour: Tonilarhodin is very strongly adsorbed on zinc 

 carbonate from benzene solution, and forms a deep-violet zone in the uppermost 

 part of the column. On alumina, the pigment is adsorbed with a light red colour. 

 The chromatogram on zinc carbonate is developed with benzene, while the 

 chromatogram on alumina is developed with a mixture of ether and methanol. 

 The pigment is eluted with a mixture of ether and acetic acid (10:1). 



Colour reactions: Torularhodin exhibits a different behaviour towards 

 antimony trichloride and towards strong acids than any other known carotenoid. 

 With antimony trichloride, a permanganate-red colouration is at first produced 

 which immediately fades. After some time the solution assumes a faint blue 

 colour. Anhydrous formic acid and concentrated sulphuric acid also decolourise 

 the yellow-red torularhodin solution ; on standing, however, a faint blue colour 

 appears. On adding trichloracetic acid to a solution of the pigment in chloro- 

 form, a faint green colouration is observed after initial bleaching. 



Detection and estimation: Torularhodin is identified by its acidic character 

 and by means of its long- wavelength spectrum. 



Torularhodin methyl ester C3gH47C02CH3 



The methyl ester is formed by the action of diazomethane on a solution of 

 torularhodin in benzene. It crystallises from a mixture of benzene and methanol 

 in dark red needles, m.p. 172-173°, uncorr. The absorption spectrum of the 

 ester differs shghtly from that of the free acid. 

 References p. 341-243. 



