The several examplcs in the literature of the conversioii of arylacetic acids to ketones by ineans of acetic anhydride have been correlated and it has been shown that this reaction, stripped to its fundamentals, is another instance of the famlhar base-catalyzed condensation of carbonyl compounds. In this instance, acid anhydride molecules function as both the addendum and the acceptor and there is presented for the reaction a mechanism, ...