288. The hydrolysis of acetic anhydride. Part II. Catalysis by pyridine

Abstract

The hydrolysis of acetic anhydride in acetone-water is strongly catalysed by small amounts of pyridine. The dependence of the reaction velocity on the concentrations of pyridine and acetic anhydride appears complex but is satisfactorily explained if the formation of catalytically inactive pyridinium acetate (by interaction of the catalyst and the product of reaction) is allowed for.IT is common knowledge that many preparative acylations are facilitated by the presence of alkali, carboxylate ions, or tertiary amines such as pyridine. The mechanism of the catalysis, superficially suggestive of general base catalysis, has not so far been elucidated and only a few isolated kinetic studies of the phenomena have been reported (e.g.

Mechanisms of Catalysis of Nucleophilic Reactions of Carboxylic Acid Derivatives.

“…However, only recently has the mechanism of the catalytic action of tertiary amines been specified. The hydrolysis of acetic anhydride in acetone-water is strongly catalyzed by small amounts of pyridine (8,176). A series of substituted pyridines of constant steric requirement catalyzes the hydrolysis of acetic anhydride, with relative rates conforming to a Brpnsted-type relationship (Section II) (177).…”

“…tended this work to include a number of acyl salicylates in a very complete investigation (169a). In the hydrolysis of acyl salicylates there exists catalysis by external hydrogen ion at low pH values (pH 1-3) and catalysis by external hydroxide ion at high pH values (pH [8][9][10][11][12][13][14]. However, from pH 4 to 8 the rate constant is independent of the pH.…”

Structure–Property Effects in the Generation of Transient Aqueous Benzoic Acid Anhydrides by Carbodiimide Fuels

“…Before designing new systems that make use of these reactions, however, it is necessary to understand the effects of changes in the substrate structure. The two individual reactions making up this system, the reactions of carbodiimides with carboxylic acids ,,− and anhydride hydrolysis, − have been extensively studied in organic chemistry for many decades but were typically studied separately. Thus, there is little data available that can be used directly to predict behavior in new out-of-equilibrium systems.…”

Structure–property Effects in the Generation of Transient Aqueous Benzoic Acid Anhydrides by Carbodiimide Fuels

“…Before designing new systems making use of these reactions, however, it is necessary to understand the effects of changes in substrate structure. The two individual reactions making up this system, the reactions of carbodiimides with carboxylic acids 28,29,[32][33][34][35][36][37][38][39][40][41][42][43] and anhydride hydrolysis, [44][45][46][47][48][49][50][51][52][53][54] have been extensively studied in organic chemistry for many decades, but were typically studied separately. Thus, there is little data available that can be used directly to predict behavior in new out-of-equilibrium systems.…”