Ester formation in neutral solution

It is generally assumed that the ionized carboxyl group R COO- is not susceptible to nucleophilic attack, and essentially all the available evidence supports this assumption. A solitary exception is discussed below (p. 160). Thus ester formation with acyl-oxygen cleavage, and oxygen exchange with the solvent, are not expected under alkaline conditions. There is no reason, however, why they should not occur in neutral solution, where a significant proportion of the undissociated acid (R COOH) is present, and both reactions are well established under these conditions. 

KINETIC DATA FOR THE O EXCHANGE REACTION OF CARBOXYLIC ACIDS IN ENRICHED WATER AT 25°C. IONIC STRENGTH 4.0 

There seems no reason to suppose that the tetrahedral intermediate formed by the addition of a hydroxide ion to the carboxylic acid should be so stabilized by the trihalomethyl group that its breakdown should be a slow hydroxide-catalyzed reaction, viz. 

This is a most unexpected reaction, and if confirmed represents an important discovery.  

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