244 CAROTENOIDS CONTAINING CARBONYL GROUPS XII 



JucKER during the chromatographic adsorption of capsochrome^' (cf. p. 248). 

 On standing in air, capsanthin is slowly oxidised. In an atmosphere of 

 oxygen, oxidation occurs more rapidly. The uptake of oxygen is complete after 

 about I month and amounts to about 29% by weight, corresponding to 10 

 mols of oxygen. The pigment wax of capsanthin is much more stable towards 

 oxygen. According to Pummerer and Rebmann^, 6-8 mols of oxygen are 

 absorbed on treating capsanthin with perbenzoic acid. On treatment with 

 bromine in chloroform solution, 8 mols of bromine are absorbed. The thermal 

 decomposition of the pigment gives rise to w-xylene. 



Derivatives 



Capsanthin diiodide: This compound is obtained on treating capsanthin 

 with iodine in carbon disulphide solution. Capsanthin diiodide crystallises in 

 flat needles which appear yellow-brown to black under the microscope^^. It is 

 easily soluble in chloroform and acetone, a little less soluble in ethanol and 

 ether and almost insoluble in petroleum ether. 



Perhydrocapsanthin: Capsanthin absorbs 10 mols of hydrogen on hydro- 

 genation in acetic acid in the presence of platinum as catalyst; the carbonyl 

 group remains unchanged. The perhydrocapsanthin thus obtained is a viscous, 

 colourless oil which is much more soluble in organic solvents than capsanthin 

 itself. On treating perhydrocapsanthin with sodium and alcohol, the carbonyl 

 group is reduced and the completely hydrogenated triol C4oHg(,03 is obtained^". 



Capsanthol C40H50O3: 



CH, CH, . CH, CH3 



C CH, CH3 CH, CH3 C 



/\ I I I I /\ 



CH2 C- CH=CH- C=CHCH=CH- C=CHCH=CHCH=C- CH=CHCH=C- CH=CH- CHOHCH^ 



HOCH C-CH3 HgC-CHa CHOH 



\ / Capsanthol \^ 



CH2 CHj 



Karrer and Hubner^^ prepared capsanthol by the reduction of capsanthin 

 with aluminium isopropoxide and isopropyl alcohol. The compound was purified 

 by repeated adsorption on calcium hydroxide from benzene solution. Capsanthol 

 crystallises from ethanol in reddish-brown leaflets, which appear yellow under 

 the microscope. Melting point 175-176" (uncorr.). Capsanthol is sparingly 

 soluble in boiling ethanol. Catalytic reduction shows the presence of 10 double 

 bonds. 

 References p. 253-255. 



