II. CHEMISTRY AND INDUSTRIAL PREPARATION 



51 



Fig. 11. Ultraviolet absorption spectra of vitamin Ai, vitamin Ao, and C22-vita- 

 min A. 



b. Structure 



Of all the structures proposed'^^ ■ ^^^- i^^-ise for vitamin A2, structures 

 XCVI, XCVII, and XCVIII will be considered. Structure XCVI was first 



H3C CH 



CH3 CH3 



I I 



— CH=CH— C=CII— CH=CH— C=CH— CII=CII— CH2OH 



CH3 



XCVI Coo-Vitamin A 



CH3 CH3 



I I 



CH=CH— C=CH— CH=CH— C=CH— CHoOH 



CH3 



XCVII Open -chain formula 



H3C CH 



>88 P. Karrer and P. Schneider, Helv. Chim. Acta 33, 38 (1950). 



