m'DROCARBON CAROTENOIDS OF THE C40 SERIES 529 



(h) Anhydro-scmi-^-caroienonc, C4nH540. Kuhn and Brockmann^- pre- 

 pared the anh.vdro compound by removal of a molecule of water from semi- 

 /3-carotenone by means of methanolic potash. The resulting product 

 ciystallizes in almost black prisms which have a greenish lustre. It melts 

 at 177°C., is readily soluble in carbon disulfide, chloroform, and benzene, 

 and dissoh'es with difficulty in hexane, petroleum ether, and absolute 

 ethanol. It is almost entirely epiphasic. 



HjC CHj H>C CHj 



n CHj CH3 CH3 CH3 r- 



/ \ hhIhhhIhhhhIhhhIhh /\ 

 HzC c-C:C'C:C'C:C'C:c-C:C'C:C-C:C-C:C-C:C-C CH? 



I II II I 



HjC C— C=0 C CHj 



I / \ / 



CHj HjC C 



»z 



Anh\dr()-scini-/3-carotenone 



(0 fi-Carotenone, C40H56O4. This tetraketone, in which both j3-ionone 

 rings of /S-carotene have been split, can be prepared through oxidation of 

 the parent hydrocarbon with chromic acid.^^-^^-*^ Semi-/3-carotenone may 

 likewise serve as the starting material in the chromic acid oxidation.** 

 j8-Carotenone separates from a benzene-ligroin mixture in crimson-red plate- 

 lets. The crystals melt at 174-17o°C. The tetraketone is adsorbed from 

 a petroleum ether solution by aluminum oxide or calcium carbonate. /3- 

 Carotenone dissolves easily in chloroform, carbon disulfide, and benzene, 

 less readily in cold methyl and ethyl alcohol, while it is very difficultly 

 soluble in hexane and petroleum ether. When it is shaken with a petro- 

 leum ether-90% methanol mixture, it is partitioned almost entirely in the 

 lower (methanol) layer. /3-Carotenone is completely without provitamin 

 A activity. 



H3C CHj H jC CHj 



C _ CHj CH3 CH3 CH3 Q Q 



/ \^H hIhhhIhhhhIhhhIh h\ / \ 

 HjC C— C :C • C: C- c: C' C: C • C: C- C: C • C: C • C: C • C: C' C GHz 



I I 



HzC 0=0 0=C GHz 



\ /• \ / \ / 



C GH3 H3G G 



H? H2 



/3-Carotenone 



(j) Bis-anhydro-^-carotenone, C40H52O2. /3-Carotenone undergoes a con- 

 densation similar to that exhibited by semi-/3-carotenone, to form the di- 

 anhydro compound. Under these conditions two molecules of water are 

 removed and two five-membered carbon rings replace the two six-membered 

 ionone rings present in the parent hydrocarbon. Kuhn and Brockmann*'^ 

 reported the synthesis of this compound by treatment of /3-carotenone with 

 methanolic potash. It crystallizes from a benzene-methanol mixture in 



