Acid anhydride

An overview of acid anhydrides in organic chemistry

Introduction

An acid anhydride is a type of chemical compound derived from an acid by the removal of a molecule of water. Acid anhydrides are commonly used in organic chemistry as reagents and intermediates in various chemical reactions. They are characterized by the presence of two acyl groups bonded to the same oxygen atom.

Structure and Nomenclature

Structure of a generic carboxylic acid anhydride.

Acid anhydrides are typically represented by the general formula (RCO)_O, where R represents an alkyl or aryl group. The nomenclature of acid anhydrides is derived from the parent carboxylic acids. For example, the anhydride formed from acetic acid is called acetic anhydride.

Types of Acid Anhydrides

Acid anhydrides can be classified into two main types:

Carboxylic Anhydrides

Carboxylic anhydrides are derived from carboxylic acids. They are the most common type of acid anhydrides and are widely used in synthesis and industrial chemistry.

Inorganic Anhydrides

Inorganic anhydrides are derived from inorganic acids such as sulfuric acid and phosphoric acid. These anhydrides are often used in chemical reactions as dehydrating agents.

Chemical Properties

Acid anhydrides are reactive compounds that readily undergo hydrolysis to form the corresponding acids. They also participate in nucleophilic acyl substitution reactions, making them valuable intermediates in the synthesis of esters, amides, and other derivatives.

Applications

Acid anhydrides are used in a variety of applications, including:

• As reagents in the synthesis of esters and amides.
• In the production of acetic anhydride, which is used in the manufacture of cellulose acetate and aspirin.
• As dehydrating agents in organic synthesis.

Safety and Handling

Acid anhydrides are typically corrosive and can cause severe irritation to the skin, eyes, and respiratory tract. Proper safety precautions, including the use of personal protective equipment (PPE), should be taken when handling these compounds.

Related Pages

• Carboxylic acid
• Ester
• Amide
• Nucleophilic acyl substitution