The interaction of acetic and trifluoroacetic anhydrides in carbon tetrachloride

Reactions of N-arylphthalamic acids with acetic anhydride

“…Similar conclusions must be reached from comparisons of experiments 12-15 with experiments 16-19. This effect was measured directly in experiments 20 and 21 which show that phthalic anhydride yields diminish as the starting concentration of la is decreased.…”

“…19 It appears, however, that the carboxylic acid behaves as a nucleophile attacking the anhydride carbonyl carbon. 20 The postulated action of the acetic acid catalyst in Scheme II is in accord with the evidence that acetic acid forms hydrogen bonds to acetic anhydride in dilute solutions of the acid in the anhydride; acetic acid dimers become more important in concentrated solutions.21 In contrast, the work of Sheinblatt and Alexander provides evidence of first-order perchloric acid catalysis of the rate of exchange of acetic acid with the acetyl groups of acetic anhydride and the kinetic analysis leads to the conclusion that protonation occurs on the acetic acid prior to the exchange reaction.18 The kinetics of this rapid reaction (mean lifetime <2 sec at 22°) are not comparable to the work described herein since the nmr method used by Sheinblatt and Alexander would not detect slower exchange reactions in the acetic acid-acetic anhydride system.18…”