530 VI. CAROTENOIDS AND RELATED COMPOUNDS 



steel-blue prism.s or platelets which melt at 209°C. It dissolves readily in 

 chloroform, benzene, and carbon disulfide, but is only slightly soluble in 

 hexane, petroleum ether, and methanol. It is almost completely epiphasic. 

 The pigment is biologically inactive. 



H3C CH3 H,C CHj 



c ch3 ch3 ch3 ch3 q 



/\ hhIhhhIhhhhIhhhIhh /\ 

 h2c c'c:c-c:c-c:c'c:c'c:c-c:c'c:c'c:c'c:c'c ch2 



I II II I 



H?C- C— C = 0=C— C CHz 



\ / 



Bi.s-nnhydro-/3-carotenone 



(k) Bis-anhydro-dihydro-^-carotenone, C40H54O2. Kuhn and Brockmann^^ 

 demonstrated the conversion of bis-anhydro-/3-carotenone to its dihydro 

 derivative when a pyridine solution was reduced on treatment with zinc 

 dust and acetic acid. The pigment can be crystallized from pyridine- 

 containing water in glistening red needles which melt at 217°C. This 

 compound dissolves well in carbon disulfide, benzene, chloroform, and 

 pyridine, but only poorly in hexane or petroleum ether. When an alkaline 

 alcoholic solution is treated with oxygen, it rapidly reverts to bis-anhydro-j8- 

 carotenone. 



HjC 



\ / 



c 

 / \ 



I 



H2C 



Bis-anhydro-diliydro-/3-carotenone 



(Z) Dihydro- ^-carotenone, C40H58O4. When /3-carotenone in a pyridine 

 solution is reduced with zinc dust and acetic acid, dihydro-j8-carotenone is 

 the resultant product.*^ The dihydro compound forms gold-yellow needle- 

 like crystals from a benzene-hexane mixture. These melt at 130°C. They 

 dissolve readily in pyridine, chloroform, and benzene, but only slightly in 

 petroleum ether and alcohols. The compound is almost completely hypo- 

 phasic. The dihydro-/3-carotenone forms a dioxime, C40H60O4N2, which 

 crystallizes in golden-yellow platelets from hot benzene, melting at 151°C. 

 The dioxime is less soluble in benzene and hexane ; it dissolves more readily 

 in alcohol than does the parent dihydro compound. 



H3C CH3 H 3C CH3 



C O CH3 CH3 CH3 Cn3 Q Q 



/ \ /^vi w i hhh i hhhh i hhh i hh^/\ 

 HjC c-c • c". c- c : c • c : c • c : c • c : c • c : c- c : c- c : c- c— c chs 



I H H I 



H?C C = 0=C CHz 



\ / \ / \ / 



C CHj H3C C 



Hi H? 



Dihydro- /3-cfirotcnone 



