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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13:04 minutes

Problem 15

Textbook Question

1. Propose a mechanism for the acid-catalyzed reaction of salicylic acid with acetic anhydride.
2. Explain why a single drop of sulfuric acid dramatically increases the reaction rate.

Verified step by step guidance

Step 1: Begin by identifying the functional groups involved in the reaction. Salicylic acid contains both a phenolic hydroxyl group (-OH) and a carboxylic acid group (-COOH). Acetic anhydride is a reactive compound with two acyl groups. The acid catalyst (sulfuric acid) will protonate key intermediates to facilitate the reaction.

Step 2: In the acid-catalyzed mechanism, sulfuric acid donates a proton (H⁺) to the carbonyl oxygen of acetic anhydride. This protonation increases the electrophilicity of the carbonyl carbon, making it more susceptible to nucleophilic attack. Represent this step using MathML:

{CH}_{3} - {CO}_{2} - {CO}_{2} + H \to {CH}_{3} - {CO}_{2} - {CO}_{2} H

Step 3: The phenolic hydroxyl group (-OH) of salicylic acid acts as a nucleophile and attacks the electrophilic carbonyl carbon of the protonated acetic anhydride. This forms a tetrahedral intermediate. Represent the nucleophilic attack using MathML:

Ar - OH + {CH}_{3} - {CO}_{2} - {CO}_{2} H \to Ar - O - {CH}_{3} - {CO}_{2}

Step 4: The tetrahedral intermediate undergoes proton transfer and elimination of acetic acid (CH₃COOH), regenerating the acid catalyst (H⁺). This step completes the formation of acetylsalicylic acid (aspirin). Represent the elimination step using MathML:

Ar - O - {CH}_{3} - {CO}_{2} \to Ar - O - {CO}_{CH} 3 + {CH}_{3} COOH

Step 5: Sulfuric acid dramatically increases the reaction rate because it acts as a strong acid, effectively protonating the acetic anhydride and stabilizing intermediates. This lowers the activation energy of the reaction, making the process faster and more efficient.

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Key Concepts

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

Acid-Catalyzed Reactions

Acid-catalyzed reactions involve the use of an acid to increase the rate of a chemical reaction. In these reactions, the acid donates protons (H+) to the reactants, enhancing their electrophilicity and facilitating the formation of intermediates. This is particularly important in organic reactions where the presence of an acid can stabilize charged intermediates, making the overall process more efficient.

Mechanism of Esterification

The mechanism of esterification describes how carboxylic acids react with alcohols or anhydrides to form esters. In the case of salicylic acid and acetic anhydride, the reaction involves the nucleophilic attack of the hydroxyl group of salicylic acid on the carbonyl carbon of acetic anhydride, leading to the formation of an ester bond and the release of acetic acid. Understanding this mechanism is crucial for predicting the products and reaction conditions.

Role of Sulfuric Acid as a Catalyst

Sulfuric acid acts as a strong acid catalyst that significantly increases the reaction rate by providing protons to the reaction mixture. This protonation enhances the electrophilic character of the acetic anhydride, making it more reactive towards nucleophilic attack. The presence of sulfuric acid also helps to remove water formed during the reaction, shifting the equilibrium towards product formation and thus accelerating the overall reaction.

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1. Propose a mechanism for the acid-catalyzed reaction of salicylic acid with acetic anhydride. 2. Explain why a single drop of sulfuric acid dramatically increases the reaction rate.

Key Concepts

Acid-Catalyzed Reactions

Mechanism of Esterification

Role of Sulfuric Acid as a Catalyst

Watch next

1. Propose a mechanism for the acid-catalyzed reaction of salicylic acid with acetic anhydride.
2. Explain why a single drop of sulfuric acid dramatically increases the reaction rate.