238 



CAROTENOIDS CONTAINING CARBONYL GROUPS 



XII 



Detection and estimation: Astacene differs from other carotenoids by its 

 single-banded spectrum and its behaviour towards alkah. 



Chemical behaviour: Astacene is very stable towards atmospheric oxygen. Its 

 general chemical behaviour is characterised by the capacity of two of the 

 carbonyl groups to enolise and of the other two carbonyl groups to undergo 

 ketonic reactions. 



Astacene dioxime CjnH=,nOjN,^": 

 CH, CH, 



^40^ ^50^-^4"^^ 2 



CHo CHo 



w ■ \V 



/\ I I I I /\ 



CH C-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-C CH 



HOC C-CH, 



\/ 



C 



II 

 NOH 



Astacene dioxime (Enol formula) 



HgC-C COH 



\/ 

 C 



i 

 NOH 



The dioxime separates from ethanol in black crystals. 



Bis-phenazine derivative CjjHjgN/^: 

 CHo CHo 



C CH, CH, 



/\ I I 



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

 N=C C-CH, 



/ \/ 



-C6H4^^N=C 



The bis-phenazine derivative was obtained by Karrer and Loewe^** by 

 warming a solution of astacene with o-phenylene diamine in glacial acetic acid 

 for one and a half hours on a water bath. The compound separates from benzene 

 in deep violet crystals. As it cannot enolise, it gives rise to a:a-dimethyl- 

 succinic acid on oxidation with permanganate (cf. p. 47), m.p. 224-225°. 

 It shows an absorption maximum in carbon disulphide at about 515 m//^^. 



Astacene diacetate C^Jil^^O^: 



This derivative is obtained by allowing a solution of astacene and acetic 

 anhydride in pyridine to stand for 16 hours^^. It crystallises from a mixture of 

 pjnridine and water in black-violet crystals, m.p. 235° (uncorr., with decom- 

 position). 



Astacene dipalmitate C^jHjogO/^ (Astacein): 



It was shown by Karrer and co-workers (cf. p. 235) that astacene (or 

 astaxanthin) occur in the lobster esterified with palmitic acid. Kuhn and co- 

 References p. 253-255. 



