Mixed carboxylic acid anhydrides: I. Acetic‐formic anhydride

Abstract The identity and purity of acetic‐formic anhydride prepared from ketene and formic acid have been established by means of N.M.R. and I.R. absorption data. On the basis of these data the presence of this mixed anhydride in the formylating reagent obtained from acetic anhydride and formic acid, could be proved and the composition of the reagent established. Indications were found, that on standing, acetic‐formic anhydride disproportionates into acetic anhydride and formic anhydride and that formic anhydride is also present in the formylating reagent.