528 VI. CAROTENOIDS AND RELATED COMPOUNDS 



from a benzene-methanol mixture in orange-red needles which melt at 

 184°C.^^'^^'*^ Oxy-/3-carotene is readily adsorbed from hexane on alumi- 

 num oxide, but not on calcium carbonate. It dissolves easily in benzene, 

 chloroform, and carbon disulfide, less readily in hexane, and it is insoluble 

 in alcohol. When partitioned between petroleum ether and 90% methanol, 

 it is found exclusively in the top layer. Oxy-j8-carotene is biologically 

 active. 



(/) Semi-^-carotenone, C40H56O2. Kuhn and Brockmann^'* prepared this 

 diketone by oxidation of /3-carotene with 0. 1 A^ chromic acid. An alterna- 

 tive procedure involves the treatment of oxy-j8-carotene in benzene with 

 lead tetraacetate in acetic acid.'^^ The compound crystallizes in four- 

 sided, crimson platelets which melt at 118-119°C. It is easily soluble in 

 hexane but dissolves more difficultly in alcohol. It shows an epiphasic 

 reaction. It is partially active as a precursor of vitamin A. 



H3C CH3 H 3C CHj 



r- -* CH3 CH3 CH3 CH3 r 



/ \^H hIhhhIhhhhIhhhIhh /\ 

 HzC C'C:C'C:C'C:C«C:C'C:C-C:C-C:C'C:C'C:C-C ZWz 



^ I II I 



HzC 0=0 C CH2 



\ / \ / \ / 



C CH3 H3C c 



H? H2 



Semi-/3-carotenone 



{g) Oxy-semi-j3-ca7'oteno7ie, C40H58O4. This compound has been prepared 

 by Kuhn and Brockmann*^ by oxidation of oxy-/3-carotene with 0.1 iV 

 chromic acid. It gives dark red or bluish shiny prisms when crystallized 

 from a benzene-petroleum ether mixture. These melt at 172°G. It dis- 

 solves readily in chloroform, more difficultly in benzene and ethanol, and 

 only slightly in petroleum ether. It gives a hypophasic reaction. 



Ox\,-senii-/3-carotenone 



