The Exchange of Carboxylic Acids with Water

The exchange of carboxylic acids with water occurs slowly at room temperature, and is acid catalyzed. A list of the conditions or rates of exchange of all carboxylic acids reported to the end of 1960 is given in Table V. Anions of carboxylic acids do not appear to exchange with water in neutral or basic solution except under very drastic conditions. 

The Kinetics of Exchange of Carboxylic Acids with Water... 

Esterification. Add-catalyzed esterification of carboxylic acid with alcohol produces water as a coproduct. However, a greener method of esterification of carboxylic acid is via the addition of olefin, which does not produce any co-products and therefore, displays 100% atom efficiency. Proton-exchanged montmorillonite (H+-mont) can be used as a catalyst for addition reactions of carboxylic acids to alkenes (Fig. 7) (38)a). For example, the reaction of benzoic acid with norbomene in the presence of the H+-mont catalyst gave 2-benzoyloxynorbomane. Even with less-reactive simple alkenes, such as cyclopentene and cyclohexene, the corresponding esters were obtained in excellent yields. 

At the end of the incubation period the fermentation culture mixture is adjusted to pH 2 with concentrated hydrochloric acid, the solid material present is removed by filtration, and the filter cake is washed with water. The washings are combined with the main filtrate, adjusted to pH 7.0, and 15.5 liters of the filtered culture liquid is introduced into a columnar exchanger d /a" i.d.) packed with 380 ml of carboxylic acid resin which has been preliminarily washed in succession with two liters of an aqueous solution of 37.5 grams of sodium hydroxide and with two liters of water. The column containing paromomycin is washed with two hold-up volumes of water and is eluted with 0.5 N hydrochloric acid. 

Two types of esterification reaction that can be studied with water as solvent are lactone formation, in which the alcohol is part of the same molecule as the acid, and the lsO-exchange reaction of carboxylic acids, which makes it possible to examine A-2 reactions of carboxylic acids under the conditions used for ester hydrolysis. Work in both these fields confirms the similarities between ester hydrolysis and formation. The hydrolysis and formation of y-butyrolactone have already been discussed (p. 109). We deal here with the lsO-exchange reactions of carboxylic acids. 

A soap is the sodium salt of carboxylic acid attached to a long, nonpolar hydrocarbon chain. When a soap is placed in hard water, the sodium cations exchange with cations such as Ca2+ and Mg2+. The resulting calcium and magnesium salts are insoluble in water and precipitate to form soap scum. ... 

A second major type of oxo trinuclear cluster is the type with two ju.3-0 caps, formed equally by molybdenum and tungsten. They are usually obtained by treating M(CO)6 with a mixture of a carboxylic acid and its anhydride, RC02H/(RC0)20, pouring the reaction mixture, after dilution with water, on a cation exchange column... 

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