Esterification of Homologous Series and the Equal Reactivity Hypothesis

2 ESTERIFICATION OF HOMOLOGOUS SERIES AND THE EQUAL REACTIVITY HYPOTHESIS [1,4,5] 

The following esterification reactions of monobasic and dibasic acids of homologous series illustrate the effect of molecular size on the rate constants  

These reaetions have been carried out in excess of ethanol with HCl catalyst, and the rates of reaction have been measured for various values of the chain length n. The reaction rate constants are evaluated using the following rate expression  

2) [—COOH] represents the total concentration of the carboxylic acid groups in the reaction mass at any time, whether present in the form of a monobasic of dibasic acid this is usually determined by titration. [H ] is the concentration of protons liberated by the hydrochloric acid. Use of the rate equation in the form shown in Eq. (3.2.2), together with experiments on monobasic and dibasic acids having different n, makes it possible to isolate the effect of the size of the molecule on k.  

The rate constants for various values of n are tabulated in Table 3.1. Two important conclusions can be drawn from the experimental results  

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