II, CHEMISTRY AND INDUSTRIAL PREPARATION 



29 



light. Mtamiu Ai is optically inactive. It is soluble in most organic solvents 

 but fails to dissolve in water, although water-soluble derivatives have been 

 prepared .^^ Vitamin Ai is unstable in the presence of oxygen or air and is 

 usually stabilized by the addition of small amounts of antioxidants such 



TABLE X 

 Properties of Vitamin Ai and Some of its Derivatives 



" In isopropanol. 



85 N. A. Milas, U. S. Pat. 2,443,373 (June 15, 1948). 



8** Although vitamin Ai is now considered to have the all-trans configuration, most of 

 the earl}^ work was done with mixtures of stereoisomers. However, it is quite pos- 

 sible that most of the derivatives which have sharp melting points have only one 

 configuration, presumably the all-trans form. 



86 J. Boldingh, H. R. Cama, F. D. Collins, R. A. Morton, N. T. Gridgeman, O. 

 Isler, M. Kofler, R. J. Taylor, A. S. Welland, and T. Bradbury, Xature 168, 598 

 (1951). 



8' H. R. Cama, F. D. Collins, and R. A. Morton, Biochem. J. 50, 48 (1951). 



88 F. P. Zscheile and R. L. Henry, Anal. Chem. 14, 422 (1942). 



89 J. G. Baxter, Fortschr. Chem. org. Naturstoffe 9, 41 (1952). 



«<> J. G. Baxter and C. D. Robeson, J.Am. Chem. Soc. 64, 2407 (1942). 



91 O. Isler, A. Ronco, W. Guex, N. C. Hindley, W. Huber, K. Dialer, and M. Kofler, 

 Helv. Chim. Acta 32, 489 (1949). 



92 O. Isler, Chimia iSivitz.) 4, 103 (1950). 



93 S. Hamano, Sci. Papers Inst. Phys. Chem. Research (Tokyo) 28, 69 (1935). 

 9* T. H. Mead, Biochem. J. 33, 589 (1939). 



95 A. R. Hanze, T. W. Conger, E. C. Wise, and D. I. Weisblat, J. Am. Chem. Soc. 70, 

 1253 (1948). 



