Preparation and stability of some esters of vitamin A.
Vitamin A esters of fatty acids having electronegative groups in the number 2 position were prepared. Acids, with chlorine or a double bond, were used and the esters were tested for stability against acid and solvolytic action. The results indicate that ( a ) stability against proton attack, in an anhydrous solvent, varies directly with the K a of the acid portion, ( b ) the addition of water to an anhydrous solvent, containing HCl, decreases the rate of formation of anhydrovitamin A, and ( c ) stability in alcoholic solvents, without an acid catalyst, varies inversely with the K a . A combined mechanism of vitamin A ester degradation in the presence of mineral acids and hydrolytic solvents is presented.