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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2:52 minutes

Problem 23a

Textbook Question

Propose mechanisms for the nucleophilic acyl substitutions to form ethyl benzoate as shown on the previous page.

Verified step by step guidance

Step 1: Identify the reactants and products. The reactant is benzoyl chloride (PhCOCl), and the product is ethyl benzoate (PhCOOCH3). The reaction involves nucleophilic acyl substitution, where the chlorine atom is replaced by a methoxy group (-OCH3).

Step 2: Recognize the role of pyridine. Pyridine acts as a base to neutralize the HCl formed during the reaction, preventing the reaction medium from becoming too acidic and facilitating the substitution process.

Step 3: Initiate the mechanism. Methanol (CH3OH) acts as the nucleophile. The lone pair of electrons on the oxygen atom of methanol 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 effect of the chlorine atom.

Step 4: Collapse of the tetrahedral intermediate. The tetrahedral intermediate undergoes rearrangement, where the chlorine atom is expelled as a leaving group. This results in the formation of the ester bond (PhCOOCH3).

Step 5: Neutralization by pyridine. Pyridine reacts with the HCl generated during the substitution, forming pyridinium chloride. This prevents the accumulation of HCl and stabilizes the reaction environment.

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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. This mechanism typically involves the formation of a tetrahedral intermediate, which then collapses to regenerate the carbonyl and expel the leaving group. Understanding this process is crucial for predicting the products of reactions involving acyl compounds.

Role of Pyridine

Pyridine is often used as a base and a catalyst in nucleophilic acyl substitution reactions. It can deprotonate the nucleophile, enhancing its nucleophilicity, and stabilize the tetrahedral intermediate formed during the reaction. Additionally, pyridine can help facilitate the departure of the leaving group, making the reaction more efficient. Recognizing the role of pyridine is essential for understanding the mechanism of the reaction leading to ethyl benzoate.

Formation of Ethyl Benzoate

Ethyl benzoate is an ester formed from the reaction of benzoic acid and ethanol, typically through nucleophilic acyl substitution. In this context, the reaction involves the nucleophilic attack of the ethoxide ion (from ethanol) on the carbonyl carbon of the acyl chloride, leading to the formation of the ester bond. Understanding the specific steps and intermediates in this transformation is key to proposing a detailed mechanism for the synthesis of ethyl benzoate.

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