Acylation of ascorbic acid in water.

The acylation of ascorbic acid by acetic anhydride was studied in water at 25 degrees. The results indicate that the initial products of reactions between these two compounds were acetic acid and 3-o-acetylascorbic acid. The latter product then underwent two parallel reactions: hydrolysis to ascorbic and acetic acids and an intramolecular O leads to O acyl migration to yield-O-acetylascorbic acid. The former reaction was predominant at pH values below 4, whereas the latter reaction predominated at pH values between 4 and 7. These results are used as a basis for questioning the structural assignments previously made to some ascorbic acid esters.