I40 CAROTENOID HYDROCARBONS OF KNOWN CONSTITUTION X 



Semi-;8-carotenone oxime crystallises from 90 % ethanol in scarlet needles, 

 m.p. 134-135° (evacuated capillary). The absorption maxima of the oxime are almost 

 identical in wavelength location with those of the parent compound. 



Neosemi-^-carotenone C40H56O2 : 



Karrer and Solmssen^^^ observed that instead of semi-jS-carotenone a 

 different compound, neosemi-j3-carotenone, can be formed by the oxidation of 

 j3-carotene with aqueous o.i N chromic acid. This compound separates from 

 methanol in almost black crystals, m.p. 143°. 



Solvent: Absorption maxima: 

 Carbon disulphide 510 479 m/i. 



Anhydrosemi-^-carotenone C40H54O : 



CH, CHo CH, CH, 



/\ r r I r /\ 



CHj C-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-C CHg 



CH2— C-CO-CHs HjC-C CHj 



Anhydrosemi-^-carotenone \^ y^ 



CHjs 



This compound is formed by splitting off a molecule of water from semi- 

 jS-carotenone by treatment with methanolic potassium hydroxide^-". The pig- 

 ment crystallises from a mixture of benzene and methanol in almost black 

 prisms, with a green lustre, m.p. 177°. It is readily soluble in carbon disulphide, 

 chloroform and benzene, and sparingly soluble in petroleum ether and absolute 

 ethanol. It is entirely epiphasic in the partition test. 



Solvent: Absorption maxiina: 



Carbon disulphide 547 509 481 m^ 



Chloroform . . ' 524 489 459 m/i 



Benzene 528 490 459 m// 



Petroleum ether 512 480 452 m^ 



^-Carotenone C40H55O4 : 



C CHo CHo CHo CHo C 



/\ I I I \ /\ 



CH2 CO-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-CO CH^ 



CH2 CO-CHg HgC-CO CHg 



\ / /9-Carotenone \ / 



CH2 CHj 



KuHN and Brockmann^^^ prepared jS-carotenone by the oxidation of 

 j3-carotene with chromic acid. It is also formed by the oxidation of semi- 

 References p. 16^-1 jo. 



