156 CAROTENOID HYDROCARBONS OF KNOWN CONSTITUTION X 



a-Carotone C4QH56O5: 



a-Carotone is formed by the oxidation of a-carotene with chromic oxide^'''. 

 It crystalHses from methanol in glittering steel-blue prisms, m.p. 148° 

 [a]g44 = +341° (± 15°). a-Carotone has no vitamin A activity. 



Solvent: Absorption maxima: 



Carbon disulphide (535) 502 471 vafx 



Chloroform 484 454 rtifx 



a-Apo-2-carotenal C30H40O: 

 CHo CHo 



\/ 



C CH3 CH, CH, CH, 



/\ I I I I 



CH2 CH- CH=CH- C=CHCH=CH- C=CHCH=CHCH=C- CH=CHCH=C- CHO 



CH2 C* CH3 



\ ^ a-Apo-2-carotenal 



CH * 



This aldehyde is formed by the potassium permanganate oxidation of 

 a-carotene. a-Apo-2-carotenal crystallises from petroleum ether in clustered 

 light red prisms, m.p. 158°. It is less easily soluble in the common solvents 

 than the y?-isomer. 



Solvent: Absorption maxima: 



Carbon disulphide 519 484 454 m^ 



Petroleum ether 479 450 m/j, 



(cf. Fig. 28, p. 359) 



a-Apo-2-carotenal oxime separates from absolute methanol in clustered red 

 leaflets, m.p. 178°. 



Md ~ +692° (± 35°) (for further data compare the original communication). 



Solvent: Absorption maxima: 



Carbon disulphide 499 469 m/n 



Petroleum ether 466 438 m/t (diffuse) 



Ethanol 469 439 m// 



By the oxidation of chromatographically unpurified carotene, von Euler, 

 Karrer and Solmssen obtained a compound which, was spectroscopically 

 indistinguishable from a-apo-2-carotenal. The analytical figures for this com- 

 pound as well as those for the oxime agreed with the calculated values for 

 a-apo-2-carotenal. This new degradation product had m.p. 174°, however, and 

 the oxime had m.p. 185°. The melting points are considerably higher than for 

 a-apo-2-carotenal. For details, compare the original communication^^^. 

 References p. 165-iyo. 



