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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4:25 minutes

Problem 6e

Textbook Question

Propose a mechanism for the reaction of aniline with ethyl acetate to give acetanilide. What is the leaving group in your proposed mechanism? Would this be a suitable leaving group for an S_N2 reaction?

Verified step by step guidance

Step 1: Understand the reaction. Aniline (C₆H₅NH₂) reacts with ethyl acetate (CH₃COOCH₂CH₃) to form acetanilide (C₆H₅NHCOCH₃). This is an example of a nucleophilic acyl substitution reaction, where the nucleophile (aniline) attacks the carbonyl carbon of ethyl acetate.

Step 2: Propose the first step of the mechanism. The lone pair of electrons on the nitrogen atom of aniline attacks the electrophilic carbonyl carbon of ethyl acetate. This forms a tetrahedral intermediate, where the carbonyl oxygen becomes negatively charged.

Step 3: Identify the leaving group. In the tetrahedral intermediate, the ethoxy group (-OCH₂CH₃) is a good leaving group. The negatively charged oxygen reforms the carbonyl bond, expelling the ethoxy group as ethanol (CH₃CH₂OH).

Step 4: Analyze the leaving group for SN2 suitability. The ethoxy group (-OCH₂CH₃) is not a suitable leaving group for an SN2 reaction because it is a strong base and does not leave easily under SN2 conditions. SN2 reactions typically require weak bases as leaving groups, such as halides (e.g., Cl⁻, Br⁻, I⁻).

Step 5: Conclude the mechanism. The final product, acetanilide, is formed after the ethoxy group leaves and the carbonyl bond is reformed. The reaction proceeds via nucleophilic acyl substitution, not an SN2 mechanism, due to the nature of the leaving group and the reaction conditions.

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Key Concepts

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

Nucleophilic Acyl Substitution

Nucleophilic acyl substitution is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an electrophilic carbonyl carbon, leading to the substitution of a leaving group. In the case of aniline reacting with ethyl acetate, the amine acts as the nucleophile, attacking the carbonyl carbon of the ester, resulting in the formation of acetanilide and the release of an acetate ion as the leaving group.

Leaving Groups

A leaving group is an atom or group that can depart with a pair of electrons in a chemical reaction, facilitating the formation of a new bond. In the proposed mechanism, the acetate ion (derived from ethyl acetate) serves as the leaving group. Good leaving groups are typically stable after departure, and acetate is considered a moderate leaving group due to its ability to stabilize the negative charge.

SN2 Reaction Mechanism

The SN2 (substitution nucleophilic bimolecular) mechanism involves a single concerted step where a nucleophile attacks an electrophile, leading to the simultaneous displacement of a leaving group. For a leaving group to be suitable for an SN2 reaction, it must be able to stabilize the transition state and depart easily. While acetate is a reasonable leaving group for many reactions, it is not ideal for SN2 due to steric hindrance and the nature of the substrate involved.

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Related Practice

Textbook Question

Show how to synthesize the following compounds, using appropriate carboxylic acids and amines.

(a)

Textbook Question

Show how to synthesize the following compounds, using appropriate carboxylic acids and amines.

(b)

Textbook Question

Show how to synthesize the following compounds, using appropriate carboxylic acids and amines.

(c)

Textbook Question

Propose a second mechanism for the reaction of benzoic acid with acetyl chloride to give acetic benzoic anhydride. This time, let the other oxygen of benzoic acid serve as the nucleophile to attack the carbonyl group of acetyl chloride. Because proton transfers are fast between these oxygen atoms, it is difficult to differentiate between these two mechanisms experimentally.

Textbook Question

Show how you would synthesize the following esters from appropriate acyl chlorides and alcohols.

(e) tert-butyl acetate

(f) diallyl succinate

Textbook Question

Show how you would use appropriate acyl chlorides and amines to synthesize the following amides.

(a) N,N-dimethylacetamide

(b) acetanilide (PhNHCOCH₃)

Textbook Question

Show how you would use acetic anhydride and an appropriate alcohol or amine to synthesize (i) benzyl acetate and (ii) N,N-diethylacetamide.

Textbook Question

Show how you would accomplish the following syntheses. Some of these conversions may require more than one step.

(e) cyclohexylamine → N-cyclohexylacetamide

(f) bromocyclohexane → dicyclohexylmethanol

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Propose a mechanism for the reaction of aniline with ethyl acetate to give acetanilide. What is the leaving group in your proposed mechanism? Would this be a suitable leaving group for an SN2 reaction?

Key Concepts

Nucleophilic Acyl Substitution

Leaving Groups

SN2 Reaction Mechanism

Watch next

Propose a mechanism for the reaction of aniline with ethyl acetate to give acetanilide. What is the leaving group in your proposed mechanism? Would this be a suitable leaving group for an S_N2 reaction?