11.4 Reactions of Carboxylic Acids

In the previous section, we learned about the general reactivity of carboxylic acids. Now, we will explore the specific reactions of carboxylic acids in detail. The reactions of carboxylic acids can be classified into three main categories based on which part of the carboxyl group is involved: reactions involving the hydrogen atom of the -OH group, reactions involving the -OH group itself, and reactions involving the carboxyl group as a whole.

Main Idea

• Acidic reactions: The hydrogen atom of the -OH group is involved (salt formation).
• Substitution reactions: The -OH group is replaced by another group (formation of carboxylic acid derivatives like acyl chlorides, esters, and amides).
• Reactions of the carboxyl group as a whole: The entire carboxyl group is modified (e.g., reduction, decarboxylation).

Core Concept

The core concept is that the carboxyl group is a composite functional group. The carbonyl part (C=O) is electrophilic and susceptible to nucleophilic attack. The hydroxyl part (-OH) is the source of acidity and can be replaced in substitution reactions. The relative reactivity of carboxylic acids depends on the ability of the -OH group to act as a leaving group, which is poor unless it is protonated or converted to a better leaving group.

Detailed Explanation

The textbook states that carboxylic acids undergo the following types of reactions.