220 CAROTENOIDS CONTAINING CARBONYL GROUPS XII 



Colour reactions: On treating an ethereal solution of the aldehyde with 

 concentrated aqueous hydrochloric acid, the latter assumes a blue colouration. 



Partition test: /3-Citraurin is hypophasic on partition between methanol and 

 petroleum ether. 



Chromatographic Properties: On chromatography from carbon disulphide, 

 j3-citraurin is adsorbed somewhat more strongly than cryptoxanthin and is 

 found above the latter, but below zeaxanthin, on the column. 



Detection and estimation: After saponification, the pigment is found in the 

 hypophasic fraction and is separated from other phytoxanthins by means of 

 chromatographic adsorption analysis. It forms a zone with a characteristic red 

 (not violet) colour, which is easily distinguishable from that of any other 

 natural carotenoid. j3-Citraurin can be identified by the determination of the 

 absorption maxima and, if necessary, by the prepartion of the oxime. 



Derivatives 

 ^-Citraurin oxime C30H41O2N: 



This compound is obtained on treating j8-citraurin with free hydroxylamine^. 

 The oxime crystallises from methanol in thin rods grouped into star-like 

 formations. M.p. 188° (corr.). 



Solvent Absorption maxima [all sharp) 



Carbon disulphide 505 473 m/t 



Benzene 487 456 m/j. 



Petrol 474 444 m^a 



Hexane 473 443 m/i 



Ethanol 476 444 m/z 



The oxime is insoluble in cold petrol. The solubility in ethanol and acetone is 

 somewhat greater. 



^-Citraurin semicarbazone C31H43O2N3*: 



The semicarbazone crystallises from benzene in microscopic reddish-brown 

 leaflets, which melt over a range near 190°. The semicarbazone is easily soluble 

 in ethanol and acetone, but sparingly soluble in petrol. 



Solvent Absorption maxima 



Carbon disulphide 517 483 m/^ (diffuse) 



Benzene 498 463 m^ (diffuse) 



Hexane 485 454 vsifi (sharp) 



Ethanol 486 454 m^ (sharp) 



References p. 253-255. 



