2 RHODOPIN 297 



CH- CH=CH- C=CHCH=CH- C=CHCH=CHCH=C- CH=CHCH=C- CH=CH- CH 



ill I I II 



C-CH, CH, CH3 CH3 CH3 HaC-C 



CH CH 



The formation of this compound from rhodoviolascin is in agreement with 

 formula I. 



Properties 



Crystalline form: Rhodoviolascin crystallises from benzene in beautifully- 

 glistening, deep red, spindle-shaped crystals. 



Melting point: 218°. 



Solubility: The pigment is almost insoluble in petroleum, ether, ligroin and 

 methanol. It is somewhat more soluble in hot benzene. 



Partition test: Rhodoviolascin is entirely epiphasic in character. 



Optical activity: At the high dilution of the pigment solution which is 

 necessary in view of the high colour intensity, no optical rotation was observed. 



Spectral properties: 



Solvent Absorption maxima 



Carbon disulphide 573.5 534 496 m/z 



Chloroform 544 507 476 m/< 



Benzene 548 511 482 n\fx 



Ethanol 526 491 (465)m/< 



(of. Fig. 25, p. 358) 



Colour reactions: With antimony trichloride in chloroform solution, a blue 

 colouration is produced with an absorption maximum at 642 m/^. 



Chromatographic behaviour: Rhodoviolascin can be easily chromatographed 

 on calcium hydroxide from benzene solution. It is adsorbed below rhodopin, 

 but above rhodopurpurin. 



2. RHODOPIN C40H58O* 



Rhodopin was first isolated by Karrer and Solmssen^^ from rhodovibrio- 

 bacteria. Later investigations have shown that this pigment is also present in 

 thiocystis-bacteria^*. 



For the isolation of rhodopin one proceeds first as in the preparation of rhodo- 

 violascin (p. 295). After the crv^stallisation of the rhodoviolascin, the petroleum 

 ether mother liquors are chromatographed on calcium hydroxide. Rhodopin is 

 eluted with a benzene-methanol mixture from the upper part of the chromatogram. 



The formula C4oH5gO is also in agreement with the analytical data. 

 References p. 341-343. 



