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

Acid-Catalyzed Ester Hydrolysis

Organic Chemistry

22. Carboxylic Acid Derivatives: NAS

Acid-Catalyzed Ester Hydrolysis

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6:14 minutes

Problem 12c

Textbook Question

The Principle of Microscopic Reversibility states that a forward reaction and a reverse reaction taking place under the same conditions (as in an equilibrium) must follow the same reaction pathway in microscopic detail. The reverse of the Fischer esterification is the acid-catalyzed hydrolysis of an ester. Propose a mechanism for the acid-catalyzed hydrolysis of ethyl benzoate, PhCOOCH₂CH₃.

Verified step by step guidance

Step 1: Protonation of the ester carbonyl group: The acid catalyst donates a proton (H⁺) to the carbonyl oxygen of ethyl benzoate (PhCOOCH₂CH₃), increasing the electrophilicity of the carbonyl carbon. This step forms a protonated intermediate.

Step 2: Nucleophilic attack by water: A water molecule acts as a nucleophile and attacks the electrophilic carbonyl carbon of the protonated ester. This results in the formation of a tetrahedral intermediate.

Step 3: Proton transfer: A proton is transferred within the tetrahedral intermediate to stabilize the structure. This step prepares the intermediate for the next step by converting the leaving group into a better leaving group.

Step 4: Elimination of ethanol: The tetrahedral intermediate collapses, expelling ethanol (CH₃CH₂OH) as a leaving group. This step regenerates the carbonyl group and forms a protonated benzoic acid intermediate.

Step 5: Deprotonation to form the product: The protonated benzoic acid intermediate loses a proton (H⁺) to regenerate the acid catalyst and form the final product, benzoic acid (PhCOOH).

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Key Concepts

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

Fischer Esterification

Fischer esterification is a chemical reaction that forms an ester from a carboxylic acid and an alcohol in the presence of an acid catalyst. This process involves the nucleophilic attack of the alcohol on the carbonyl carbon of the carboxylic acid, leading to the formation of an ester and water. Understanding this mechanism is crucial as it provides the reverse reaction pathway for hydrolysis.

Microscopic Reversibility

The Principle of Microscopic Reversibility states that the detailed steps of a forward reaction are mirrored in the reverse reaction under the same conditions. This principle implies that the transition states and intermediates involved in the forward reaction will also be present in the reverse reaction, allowing for a deeper understanding of reaction mechanisms and equilibrium.

Acid-Catalyzed Hydrolysis

Acid-catalyzed hydrolysis is a reaction where an ester reacts with water in the presence of an acid catalyst to produce a carboxylic acid and an alcohol. This process involves protonation of the carbonyl oxygen, making the carbonyl carbon more electrophilic, followed by nucleophilic attack by water. Recognizing this mechanism is essential for proposing the hydrolysis pathway of esters like ethyl benzoate.

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