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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3:27 minutes

Problem 19a

Textbook Question

Which ester hydrolyzes more rapidly? a. methyl acetate or phenyl acetate?

Verified step by step guidance

Step 1: Understand the concept of ester hydrolysis. Ester hydrolysis involves breaking the ester bond (C-O bond) in the presence of water or a base/acid catalyst. The rate of hydrolysis depends on the electronic and steric effects of the substituents attached to the ester group.

Step 2: Analyze the structures of methyl acetate and phenyl acetate. Methyl acetate has a methyl group (-CH3) attached to the oxygen atom, while phenyl acetate has a phenyl group (-C6H5) attached to the oxygen atom.

Step 3: Consider the steric effects. The phenyl group is bulkier than the methyl group, which can hinder the approach of water or hydroxide ions to the ester bond, slowing down the hydrolysis reaction.

Step 4: Evaluate the electronic effects. The phenyl group can stabilize the transition state through resonance, but it also withdraws electron density from the ester bond, making it less reactive compared to the methyl group in methyl acetate.

Step 5: Conclude that methyl acetate hydrolyzes more rapidly than phenyl acetate due to the smaller steric hindrance and higher reactivity of the methyl group compared to the phenyl group.

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Key Concepts

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

Ester Hydrolysis

Ester hydrolysis is a chemical reaction where an ester reacts with water to form an alcohol and a carboxylic acid. This reaction can occur under acidic or basic conditions and is crucial in organic chemistry for understanding the reactivity of esters. The rate of hydrolysis can vary significantly based on the structure of the ester, particularly the nature of the alkyl groups attached to the ester functional group.

Electronic Effects

Electronic effects, such as inductive and resonance effects, influence the stability of the transition state during hydrolysis. In the case of methyl acetate versus phenyl acetate, the presence of the phenyl group can stabilize the transition state through resonance, making the hydrolysis slower compared to the more straightforward methyl group. Understanding these effects is essential for predicting the reactivity of different esters.

Steric Hindrance

Steric hindrance refers to the prevention of chemical reactions due to the spatial arrangement of atoms within a molecule. In the context of ester hydrolysis, bulky groups can hinder the approach of water molecules to the ester bond, slowing down the reaction. Comparing methyl acetate, which has less steric hindrance, to phenyl acetate, which has a larger phenyl group, highlights how steric factors can affect hydrolysis rates.

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Textbook Question

Propose mechanisms for the following reactions.

(d)

Textbook Question

The mechanism for acidic hydrolysis of a nitrile resembles the basic hydrolysis, except that the nitrile is first protonated, activating it toward attack by a weak nucleophile (water). Under acidic conditions, the proton transfer (tautomerism) involves protonation on nitrogen followed by deprotonation on oxygen. Propose a mechanism for the acid-catalyzed hydrolysis of benzonitrile to benzamide.

Textbook Question

Compare each of the mechanisms listed here with the mechanism for each of the two parts of the acid-catalyzed hydrolysis of an ester, indicating a. similarities. b. differences.

4. acid-catalyzed hydrolysis of an amide

Textbook Question

What products would you expect to obtain from the following reactions?

c. urea + water

d. β-ethylglutaric acid + acetyl chloride + Δ

Textbook Question

Which ester hydrolyzes more rapidly? b. phenyl acetate or benzyl acetate?

Textbook Question

Compare each of the mechanisms listed here with the mechanism for each of the two parts of the acid-catalyzed hydrolysis of an ester, indicating a. similarities. b. differences.

1. acid-catalyzed formation of a hydrate

Textbook Question

For each heterocyclic compound,

(ii) show what compounds would result from complete hydrolysis.

(a)

(b)

(c)

Textbook Question

How could you convert N-methylbenzamide to the following compounds?

b. benzoic acid

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