Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

22. Carboxylic Acid Derivatives: NAS

Nucleophilic Acyl Substitution

Organic Chemistry

22. Carboxylic Acid Derivatives: NAS

Nucleophilic Acyl Substitution

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7:33 minutes

Problem 46a

Textbook Question

Propose a mechanism for the formation of succinic anhydride from succinic acid in the presence of acetic anhydride at neutral pH.

Verified step by step guidance

Identify the functional groups in succinic acid and acetic anhydride. Succinic acid contains two carboxylic acid groups (-COOH), while acetic anhydride is a reactive anhydride that can act as an acylating agent.

Recognize the role of acetic anhydride in the reaction. Acetic anhydride reacts with one of the carboxylic acid groups of succinic acid to form an intermediate mixed anhydride. This step involves nucleophilic attack by the carboxylate oxygen of succinic acid on the carbonyl carbon of acetic anhydride, followed by the departure of an acetate ion.

Propose the cyclization step. The second carboxylic acid group of succinic acid acts as a nucleophile, attacking the carbonyl carbon of the mixed anhydride intermediate. This intramolecular nucleophilic acyl substitution leads to the formation of a five-membered ring structure, which is succinic anhydride.

Account for the neutral pH condition. At neutral pH, the reaction proceeds without the need for additional acid or base catalysts because acetic anhydride is sufficiently reactive to facilitate the formation of the mixed anhydride and subsequent cyclization.

Conclude the mechanism by noting the byproduct. The reaction releases acetic acid as a byproduct when the acetate ion from acetic anhydride combines with a proton from the reaction intermediates.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Carboxylic Acids and Anhydrides

Carboxylic acids, like succinic acid, contain a carboxyl group (-COOH) that can undergo dehydration to form an anhydride. Anhydrides are formed when two carboxylic acid molecules lose a water molecule, resulting in a compound with two acyl groups. Understanding the structure and reactivity of these functional groups is essential for proposing a mechanism for the transformation.

Nucleophilic Acyl Substitution

Nucleophilic acyl substitution is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks the carbonyl carbon of an acyl compound, leading to the substitution of a leaving group. In the case of succinic acid and acetic anhydride, the hydroxyl group of succinic acid can be replaced by an acetic group, facilitating the formation of succinic anhydride. This concept is crucial for understanding how the reaction proceeds.

Dehydration Reactions

Dehydration reactions involve the removal of water from a molecule, often leading to the formation of a double bond or a cyclic structure. In the context of succinic acid and acetic anhydride, the dehydration step is key to forming succinic anhydride, as it involves the elimination of water during the reaction. Recognizing the role of dehydration in organic transformations is vital for grasping the proposed mechanism.

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