Esters and the Fischer Esterification

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In the procedure described in this section, you will perform the Fischer esterification of p-aminobenzoic acid (16) with ethanol to give ethyl p-aminobenzoate (17), more commonly known as benzocaine, according to Equation 20.4. Benzocaine is a useful topical anesthetic, and the discovery of its anesthetic properties represents an interesting example of rational drug design as described in the Historical Highlight at the end of this chapter. 

The equlibrium between the starting materials and products is readily established by heating a mixture of 16 and ethanol under reflux in the presence of a catalytic amount of sulfuric acid to give 17 and water (Eq. 20.4). However, if a microwave apparatus is available for heating (Sec. 2.9), the reaction can be effected in a pressurized vial. It is instructive to compare the reaction times required and the results obtained using conventional versus microwave heating for promoting the reaction. 

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