Advanced Topic 814 of 1102 Organic Chemistry
Acid Chlorides and Anhydrides
Highly reactive acid derivatives used for acylation.
In-depth explanation of Acid Chlorides and Anhydrides
Acid chlorides and acid anhydrides are the most reactive carboxylic acid derivatives, because chloride and carboxylate are good leaving groups. They undergo nucleophilic acyl substitution rapidly with water, alcohols and amines, giving carboxylic acids, esters and amides respectively. Acid chlorides are usually made by treating a carboxylic acid with thionyl chloride, SOCl2, which produces only gaseous by-products. These compounds are used in acylation reactions, where an acyl group is transferred to a nucleophile.
Going deeper: Acid Chlorides and Anhydrides
Key ideas: These are the most reactive carboxylic acid derivatives: acid chloride > anhydride > ester > amide. Made by RCOOH with SOCl2 (gaseous by-products) or PCl5. They react with water to give acid, alcohol to ester, ammonia to amide (use two equivalents of amine to absorb HCl), and benzene under AlCl3 to ketone. Acetic anhydride acetylates salicylic acid to aspirin.
Common mistakes and connections: Students leave acid chlorides in water, or try to make acid chlorides from esters. Another error is writing the wrong leaving group or forgetting HCl is formed. Links to acyl nucleophilic substitution, Friedel-Crafts acylation and aspirin synthesis.
Visualization of Acid Chlorides and Anhydrides
Acid chlorides are the most reactive carboxylic acid derivatives, then anhydrides, esters and amides, so each can make the less reactive ones. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Acetic anhydride is used to acetylate salicylic acid in the industrial synthesis of aspirin.
Frequently asked questions about Acid Chlorides and Anhydrides
What is Acid Chlorides and Anhydrides?
Highly reactive acid derivatives used for acylation.
Is Acid Chlorides and Anhydrides a beginner, intermediate or advanced topic?
Acid Chlorides and Anhydrides is a advanced topic in Organic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Acid Chlorides and Anhydrides?
Study these earlier topics in Organic Chemistry first: Hydrolysis of Esters, Saponification, Soaps and Detergents.
What comes after Acid Chlorides and Anhydrides?
The next topics in Organic Chemistry are Amides and Amines.
Can I practise Acid Chlorides and Anhydrides with quizzes?
Yes. The interactive lesson includes a self-check question on Acid Chlorides and Anhydrides, and the Organic Chemistry quiz draws on every topic in this area.
Where Acid Chlorides and Anhydrides fits in Organic Chemistry
Acid Chlorides and Anhydrides is topic 86 of 148 in Organic Chemistry.