PROPERTIES OF VITAMINS A AND RELATED COMPOUNDS 



735 



Further light on the structure of anhydrovitamin A is afforded by the 

 synthesis of an unsaturated hydrocarbon related to vitamin A, by Karrer 

 et al}^^''^^'^ The compound was prepared by synthesis or by partial hydro- 

 genation of anhydrovitamin A. 



(6) Properties of Anhydrovitamin A. The most characteristic property 

 of anhydrovitamin A is its absorption spectrum. In contradistinction to 

 the single maximum absorption peak of either vitamin Ai or vitamin Ao, 

 anhydrovitamin A shows 3 or 4 maxima which have a much sharper struc- 

 ture. Although a number of values for absorption maxima have been 



4000 



3000 



2000 





1000 - 



300 

 Wave length, mM. 



400 



Fig. 8. Absorption spectra of: (1) vitamin A, and (2) 

 anhydrovitamin A in absolute ethyl alcohol. ^^* 



recorded/ ''^•*°' ^^^'2^^ the values obtained on the crystalline product by 

 Shantz ei al^^'" are probably the most reliable. These absorption maxima 

 are 351, 371, and 392 m/i, and the corresponding E (1%, 1 cm.) values are 

 2500, 3650, and 3180, respectively. The absorption pattern for anhydro- 

 vitamin A is given in Figure 8. 



The band at 392 m/x is always well defined, but the maximum at 351 m/x 

 may be a sharp peak or only a marked inflection. Anhydrovitamin A 

 reacts with antimony tiichloride to give a peak having a maximum at the 

 same wave length as that of vitamin A (020 m/i). The extinction value, 

 E (1%, 1 cm.), of the anhydrovitamin A-antimony trichloride product is 



2^s P. Karrer and K. Schwvzer, Helv. Chim. AcUi, 31, 1055-1062 (1948). 

 2« P. Karrer and J. Benz, Helv. Chim. Acla, 31, 1048-1054 (1948). 



