I20 CAROTENOID HYDROCARBONS OF KNOWN CONSTITUTION X 



TABLE 31 



COMPOSITION OF THE TOMATO PIGMENTS (kUHN AND GRUNDMANN) 



Properties and physical constants 



Crystalline form: Lycopene crystallises from a mixture of carbon disulphide 

 and ethanol in long red needles. From petroleum ether it crystallises in charac- 

 teristic felted hair-like needles, or occasionally in long dark red-violet prisms. 

 In powder form, it is a dark reddish-brown. In contrast to most carotenoids, 

 crystals of lycopene show little metallic lustre. (For X-ray diffraction pattern, 

 see Mackinney^*'.) 



Melting point: 170° (uncorr.)^?; 173° (uncorr.)28; 174° (corr.)^^; 175° (corr.)^*'. 



Solubility: 



Ethanol, cold almost insoluble 



Ethanol, hot very sparingly soluble 



Methanol almost insoluble 



Benzene, cold fairly soluble 



Benzene, hot very soluble 



Chloroform, cold easily soluble 



Chloroform, hot very easily soluble 



Carbon disulphide very easily soluble 



1 g of lycopene is soluble in 50 ml of cold carbon disulphide, 3 1 of boiling 

 ether, 10-12 1 of boiling petroleum ether, or 14 1 of hexane of 0°3i. 



Spectral properties: 



Solvent: Absorption maxima: 



Carbon disulphide 548 507.5 477 m/^ 



Chloroform 517 480 453 m/i 



Benzene 522 487 455 m/t 



Petroleum ether 506 475.5 447 m/x 



Ethanol 503 472 443 m^ 



Hexane 504 472 443 m^ 



(cf. Fig. 4, p. 349, and Fig. 31, p. 361) 

 Colour of solutions: 



In carbon disulphide blue with a red tinge 



In ether (saturated solution) . . . bluish-red 

 In ethanol (hot saturated solution) dark yellow 



References p. 165-iyo. 



