Acid-Catalyzed Ester Hydrolysis and Transesterification

We have seen that it is necessary to use excess amine in the reaction of an acyl chloride with an amine. Explain why it is not necessary to use excess alcohol in the reaction of an acyl chloride with an alcohol. 

List the following esters in order from most reactive to least reactive toward hydrolysis  

Solution We know that the reactivity of a carboxylic acid derivative depends on the basicity of the group attached to the acyl group—the weaker the base, the easier it is for both steps of the reaction to take place (Section 16.6). So now we need to compare the basicities of the three phenolate ions. 

We have seen that esters hydrolyze slowly because water is a poor nucleophile and esters have relatively basic leaving groups. The rate of hydrolysis can be increased by either acid or hydroxide ion. When you examine the mechanisms for these reactions, notice the following features that hold for all organic reactions  

All organic intermediates and products in acidic solutions are positively charged or neutral negatively charged organic intermediates and products are not formed in acidic solutions. 

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