HYDROCARBON CAROTENOIDS OF THE C40 SERIES 515 



shown by Zechmeister et a/.59,63,64 ^^q ]jq h^ q^^ ^j^g basis of hydrogenation 

 tests. Confirmation of this finding was given by Pummerer and Rebmann,®^ 

 who proved that /3-carotene is capable of absorbing a maximum of 1 1 mole- 

 cules of iodine. 



Since the completely saturated hydrocarbon perhydrocarotene has an 

 empirical formula of C40H78, it was suggested that two ring structures occur 

 in the |3-carotene molecule. ^^ The nature of such ring stmctures was indi- 

 cated by the fact that geronic acid and other characteristic derivatives 

 originate on oxidation of jS-carotene with potassium permanganate or 

 ozone.^®~^^ All of these products originate through the oxidation of ^- 



ionone and, in fact, their proportions are similar to those produced when /3- 

 carotene is oxidized. Since pure jS-carotene gives rise to 16% of geronic 

 acid on oxidation, calculated on the basis of two /3-ionone rings, while 

 j3-ionone itself was shown to produce 19.4% under similar conditions, 

 Karrer and Morf ^^ concluded that /3-carotene possesses two ionone residues, 



HjC CHj 



\ / 



c 

 / \ 



H,C C 



I II 



H,C C 



\ /\ 

 C CHs 

 Hz 



/3-Ionone residue 



Further proof of the structure of /3-carotene is furnished by degradation 

 tests with potassium permanganate. Under this treatment, four molecules 

 of acetic acid originate."'^' One acetic acid molecule is formed from the 

 following group : 



6« L. Zechmeister and L. v. Cholnoky, Ber., 61, 1534-1539 (1928). 

 «« L. Zechmeister, L. v. Cholnoky, and V. VraMly, Ber., 66, 123-124 (1933). 

 «5 R. Pummerer and L. Rebmann, Ber., 61, 1099-1102 (1928). 

 6« P. Karrer and R. Morf, Helv. Chim. Acta, I4, 1033-1036 (1931). 

 " P. Karrer and A. Helfenstein, Helv. Chim. Acta, 12, 1142-1144 (1929). 

 " P. Karrer, A. Helfenstein, H. Wehrli, and A. Wettstein, Helv. Chim. Acta, 13, 1084- 

 1099 (1930). 



«» J. H. C. Smith and H. A. Spoehr, ./. Biol. Chem., 86, 755-760 (1930). 



