HYDROCARBON C'AROTENOIDS OF THE C40 SERIES 543 



later from ilic tomato by Millardot.'-"^ The latter worker called it "solano- 

 rubin." Schunck'-^" recognized that the tomato pigment, which he called 

 lycopene, differed in absorption spectrum from carotene. The empirical 

 formula of C'-KiHbfi was esta])lished by Willstatter and I*]scher"'' who recog- 

 nized tliat lycopene is an isomer of the caroten(\s. 



a. Structure. The structure of lycopene was largely worked out by 

 Karrer and his co-workers. Karrer and Widmer^'^ demonstrated that, on 

 catalytic liydrogenation, lycopene takes up 13 molecules of hydrogen to 

 form perhydrolycopene, which has the formula C40H82. This latter com- 

 pound is a paraffin in the form of a colorless, optically inactive oil boiling at 

 238-240°C. at 0.03 mm. These results indicate not only that lycopene 

 differs from /3-carotene in having 13 instead of 11 double bonds, but also in 

 the fact that the molecule contains no cyclic structures. The ends of the 

 molecule were shown to be identical, since on ozonization it yields 1.6 mole- 

 cules of acetone. ^'^ This would indicate that both terminal groups are 

 (CH3)2CH=. The formation of succinic acid on oxidation with potassium 

 permanganate suggests the presence of the group =^CHCH2-CH.:CH=; 

 on treatment with chromic acid, 6 molecules of acetic acid are produced. 

 Karrer et a/.^**'^'^ first suggested the structure which appears to explain the 

 properties and reactions of tliis pigment. The Karrer formula has been 

 further substantiated by the demonstration by Kuhn and Grundmann^^" 

 that, on partial oxidation of lycopene with chromic acid, methylheptenone 

 and an aldehyde, lycopenal, are formed. On further oxidation in benzene, 

 lycopenal disappears and bixin dialdehyde is produced, together with an 

 additional molecule of methylheptenone.'^^ 



Lycopene 



2'5 A. Millardet, Bull. soc. Nancy [2], 1, No. Ill, 21 (1875). Cited by P. Karrer and 

 E. Jucker, Carotinoide, p. 113. 



"« C. A. Schunck, Proc. Roy. Soc. London, 72, 165-176 (1903). 



2" R. Willstatter and H. H. Escher, Z. physiol. Chem., 64, 47-61 (1910). 



2»8 p. Karrer and R. Widmer, Helv. Chim. Acta, 11, 751-752, 752-754 (1928). 



219 P. Karrer, A. Helfenstein, B. Pieper, and A. Wettstein, Helv. Chim. Acta, I4, 435- 

 438 (1931). 



"« R. Kuhn and C. Grundmann, Ber., 65, 898-902 (1932). 



''"i R. Kuhn and C. Crundmann, Ber., 65, 1880-1889 (1932). 



