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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3:09 minutes

Problem 37

Textbook Question

Diazomethane can be used to convert a carboxylic acid to a methyl ester. Propose a mechanism for this reaction.

Verified step by step guidance

Step 1: Identify the reactants and products. The reactants are a carboxylic acid and diazomethane (CH₂N₂). The product is a methyl ester, along with nitrogen gas (N₂) as a byproduct.

Step 2: Recognize the role of diazomethane. Diazomethane is a highly reactive compound that acts as a methylating agent. It donates a methyl group to the carboxylic acid, converting it into a methyl ester.

Step 3: Initiate the mechanism. The carboxylic acid's hydroxyl group (-OH) acts as a nucleophile and attacks the electrophilic carbon in diazomethane. This leads to the formation of a tetrahedral intermediate.

Step 4: Rearrange the intermediate. The intermediate undergoes a rearrangement where the nitrogen atoms in diazomethane are expelled as nitrogen gas (N₂), leaving behind the methyl group attached to the oxygen atom of the carboxylic acid.

Step 5: Finalize the product. The methyl group is now bonded to the oxygen atom of the carboxylic acid, forming the methyl ester. The reaction is complete, and nitrogen gas is released as a byproduct.

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Key Concepts

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

Carboxylic Acids

Carboxylic acids are organic compounds characterized by the presence of a carboxyl group (-COOH). They are known for their acidic properties due to the ability to donate a proton (H+) from the hydroxyl part of the carboxyl group. In the context of the reaction with diazomethane, the carboxylic acid acts as the starting material that will be converted into an ester.

Diazomethane

Diazomethane (CH2N2) is a highly reactive compound used in organic synthesis, particularly for methylation reactions. It contains a diazo group, which makes it a good methylating agent. In the proposed reaction, diazomethane reacts with the carboxylic acid to form a methyl ester, releasing nitrogen gas (N2) as a byproduct.

Esterification Mechanism

The esterification mechanism involves the nucleophilic attack of the diazomethane on the carbonyl carbon of the carboxylic acid. This process typically includes the formation of a tetrahedral intermediate, followed by the elimination of water and the formation of the ester bond. Understanding this mechanism is crucial for proposing a detailed reaction pathway for the conversion of carboxylic acids to esters using diazomethane.

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Propose a mechanism for each of the following reactions:

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Predict the products of the following reactions.

(j)

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(i)

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There are many methods for activating a carboxylic acid in preparation for coupling with an amine. The following method converts the acid to an N-hydroxysuccinimide (NHS) ester.

(b) Propose a mechanism for the reaction shown.

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