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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3:40 minutes

Problem 23b

Textbook Question

Propose mechanisms for the nucleophilic acyl substitutions to form N-methylacetamide as shown on the previous page.

Verified step by step guidance

Step 1: Identify the starting material and the product. The starting material is benzoyl chloride (PhCOCl), and the product is N-methylacetamide (PhCONHCH3). This reaction involves nucleophilic acyl substitution, where the chlorine atom is replaced by the N-methylamide group.

Step 2: Recognize the nucleophile and base. Methylamine (CH3NH2) acts as the nucleophile, and sodium hydroxide (NaOH) serves as the base to neutralize the HCl byproduct formed during the reaction.

Step 3: Initiate the mechanism with the nucleophilic attack. The lone pair of electrons on the nitrogen atom of CH3NH2 attacks the carbonyl carbon of benzoyl chloride, forming a tetrahedral intermediate. This step is driven by the electrophilic nature of the carbonyl carbon due to the electron-withdrawing chlorine atom.

Step 4: Collapse of the tetrahedral intermediate. The tetrahedral intermediate collapses, expelling the chloride ion (Cl⁻) as a leaving group and forming the amide bond (C-N). This step restores the carbonyl group in the product.

Step 5: Neutralization of the byproduct. The expelled HCl reacts with NaOH to form NaCl and water, ensuring the reaction proceeds efficiently without acid buildup. The final product, N-methylacetamide, is formed.

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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 in organic chemistry where a nucleophile attacks the carbonyl carbon of an acyl compound, leading to the replacement of a leaving group (such as a halide) with the nucleophile. This mechanism is crucial for forming amides, esters, and other derivatives from carboxylic acids and their derivatives.

Mechanism Steps

The mechanism of nucleophilic acyl substitution typically involves several key steps: nucleophilic attack on the carbonyl carbon, formation of a tetrahedral intermediate, and subsequent elimination of the leaving group. Understanding these steps is essential for predicting the outcome of the reaction and the stability of intermediates formed during the process.

Role of Base Catalysis

In the provided reaction, sodium hydroxide (NaOH) acts as a base that can deprotonate the nucleophile (methylamine, CH3NH2), enhancing its nucleophilicity. Base catalysis is often employed in nucleophilic acyl substitutions to facilitate the reaction by increasing the reactivity of the nucleophile and stabilizing the transition state.

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