3 p-CAROTENE 137 



zene and ether, but only sparingly soluble in cold methanol and ethanol. 

 Perhydrocarotene is optically inactive. According to von Euler, Demole, 

 Karrer and Walker^*^ it possesses no biological activity. 



Dehydro-^ -carotene (Isocarotene) C40H54: 



This hydrocarbon is formed by the decomposition of iodine addition 

 products of j6-carotene with thiosulphate, acetone, mercury or finely divided 

 silver^ *'^. 



According to Karrer and Schwab^^", dehydro-^-caiotene has the following 

 constitution* : 



CH3 CH3 CH3 CH, 



C CH3 CH3 CH3 CH3 C 



/\ II II /\ 



CH~ C=CHCH=C-CH=CHCH=C-CH=CHCH=CH-C=CHCH=CH-C=CHCH=C CHg 



11 II 



CHj C-CH3 HgC-C CH, 



\ ^ Dehydro-^-carotene (Isocarotene) %^ y^ 



CH CH 



Dehydro-j8-carotene crystallises from petroleum ether in glistening violet- 

 blue needles or plates, and from a mixture of benzene and methanol in 

 violet prisms, m.p. 192-193° (corr., Karrer, Schopp and Morf)!^^ It is very 

 sparingly soluble in petroleum ether, but easily soluble in benzene and chlo- 

 roform. It is practically insoluble in alcohols. 



Solvent: Absorption maxima: 



Carbon disulphide 543 504 472 m/i 



Petroleum ether 504 475 447 m/z 



Chloroform 518 485 455 m/z 



(of. Fig. 31, p. 361) 



Quantitative extinction measurements have been recorded by Hausser and 

 Smakula^i^. With antimony trichloride in chloroform, isocarotene gives a stable 

 blue colouration. It exhibits no vitamin A activity. 



'p-Carotene oxide' C4oH5gO: 



This compound was obtained by von Euler, Karrer and Walker^^^ by 

 the oxidation of ^-carotene with perbenzoic acid. It is not an epoxide as was at 

 first assumed, but a furanoid oxide of the following constitution (Karrer and 



JUCKER^^*). 



* According to H. v. Euler, P. Karrer and O. Walker, Helv. chim. Acta 15 (1932) 

 1507, small amounts of isocarotene are formed by the oxidation of /5-carotene with per- 

 benzoic acid. 



References p. 16^-iyo. 



