Carboxylic Acids: Essential Organic Compounds

Introduction

Carboxylic acids represent a fundamental class of organic compounds characterized by the presence of a carboxyl group (-COOH). These compounds play crucial roles in biological systems and industrial processes, from amino acids to fatty acids.

Structure and Nomenclature

The carboxyl group consists of a carbonyl group (C=O) directly bonded to a hydroxyl group (-OH). The carbon atom in the carboxyl group is sp² hybridized, creating a planar geometry around the carbon atom.

Naming Conventions

Properties of Carboxylic Acids

Acid Strength and Dissociation

Carboxylic acids are weak acids that dissociate in water according to the equilibrium:

$\text{RCOOH}_{(aq)} + \text{H}_2\text{O}_{(l)} \rightleftharpoons \text{RCOO}^-_{(aq)} + \text{H}_3\text{O}^+_{(aq)}$

The acidic nature arises from two key factors:

Factors Affecting Acid Strength

Physical Properties

Boiling and Melting Points

Carboxylic acids exhibit higher boiling points compared to similar molecular weight alcohols due to:

The unique dimer formation involves two hydrogen bonds between two carboxylic acid molecules:

$\text{R-COOH} \cdots \text{HOOC-R}$

Solubility

Reactions

1. Acid-Base Reactions

Carboxylic acids react with bases to form salts:

With metal hydroxides: $\text{RCOOH} + \text{MOH} \rightarrow \text{RCOOM} + \text{H}_2\text{O}$

With carbonates: $2\text{RCOOH} + \text{M}_2\text{CO}_3 \rightarrow 2\text{RCOOM} + \text{CO}_2 + \text{H}_2\text{O}$

With hydrogen carbonates: $\text{RCOOH} + \text{MHCO}_3 \rightarrow \text{RCOOM} + \text{CO}_2 + \text{H}_2\text{O}$

2. Formation from Oxidation

Primary alcohols can be oxidized to form carboxylic acids: $\text{RCH}_2\text{OH} \xrightarrow[\text{H}^+/\text{KMnO}_4]{\text{oxidation}} \text{RCOOH}$

Common oxidizing agents include: