142 CAROTENOID HYDROCARBONS OF KNOWN CONSTITUTION X 



This compound is formed by shaking bis-anhydro-/3-carotenone with zinc 

 dust in a mixture of pyridine and glacial acetic acid^^e^ -pj^g pigment crystallises 

 from aqueous pyridine in brilliant red needles, m.p. 217° (corr., evacuated 

 capillary) . Dihydro-bis-anhydro-/3-carotenone is readily soluble in carbon di- 

 sulphide, benzene, chloroform and pyridine, but only sparingly soluble in petrol 

 and petroleum ether. It is rapidly oxidised by air in alkaline alcoholic solution 

 to bis-anhydro-/S-carotenone. 



Solvent: Absorption maxima: 



Carbon disulphide 510 478 448 m/^ 



Chloroform 490 459 430 mfi 



Benzene 492 460 430 m/i 



Petrol 479 448 421 m/< 



Dihydro-^-carotenone C^f^^fii'. 

 CH, CH, CH, CH, 



C CH3 CH3 CH3 CH3 C 



/\ I I I I /\ 



CHa CO-CH2CH=C-CH=CHCH=C-CH=CHCH=CH-C=CHCH=CH-C=CH-CH2-CO CHj 



CHg CO-CHs H3C-C0 CHj 



\ / Dihydro-;S-carotenone \ / 



CHa CHa 



Dihydro-j5-carotenone is formed by the reduction of /9-carotenone with zinc 

 dust in pyridine and glacial acetic acid^^'. The pigment crystallises from a 

 mixture of petrol and benzene in golden-yellow needles, m.p. 130° (corr. 

 evacuated capillary). It is readily soluble in pyridine, chloroform and benzene, 

 but only sparingly soluble in petroleum ether and alcohols. It is almost entirely 

 hypophasic in the partition test. 



Solvent: Absorption maxima: 



Carbon disulphide 454.5 426 m/i 



Chloroform 435 411 m/i 



Hexane 426 m/t 



Petrol 429 m/^ 



Benzene 436 411 m/i 



Petroleum ether 424 m/t 



On treatment with hydroxylamine, dihydro-/5-carotenone forms a dioxime 

 C4oHgo04N2, which crystallises from hot benzene in golden-yellow plates, m.p. 

 151° (corr., evacuated capillary). The dioxime is less readily soluble in petrol 

 and benzene and more readily soluble in alcohol than dihydro-/5-carotenone. 



Solvent: Absorption maxima: 



Carbon disulphide 454.5 426 m/i 



Petrol 429 m/i 



Ethanol 426 m/i 



References p. 165-iyo. 



