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Acyl Trifluoroacetates. Part 1V.l Trifluoroacetylation of Hydroxycompounds w i t h Trifluoroacetic Anhydride By T. G. Bonner," P. M. McNamara, and (in part) B. Smethurst, Royal Holloway College, University of Alcohols and phenols are trifluoroacetylated in carbon tetrachloride much more rapidly by trifluoroacetic anhydride than by acetyl trifluoroacetate. Pyridine bases are effective catalysts for the trifluoroacetylation of phenols but not of alcohols or thiophenoi, and this effect is attributed to phenolic compounds showing greater nucleophilicity through hydrogen-bonding with the base.London, Englefield Green, Egham, Surrey THE fact that hydroxy-compounds are more rapidly trifluoroacetylated by trifluoroacetic anhydride than by acetyl trifluoroacetate in carbon tetrachloride must arise, at least partly, because the trifluoroacetate anion is a better leaving-group 2*3 than the acetate ion. The importance of this effect is evident from the very similar rates in carbon tetrachloride at 0" of acetylation of 9-chlorophenol by acetyl trifluoroacetate (1.1 x 10-4 sec.-l) and of trifluoroacetylation of the same substrate by trifluoroacetic anhydride (0.9-1*0 x sec.-l). The rate in both cases appears to depend markedly on the bond-breaking step in the anhydride.The change from predominant acetylation of phenols by acetyl trifluoroacetate to a faster trifluoroacetylation reaction on addition of pyridine bases has been attributed t o an increase in the nucleophilicity of the hydroxy-Part 111, T.

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