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

21. Aldehydes and Ketones: Nucleophilic Addition

Addition of Amine Derivatives

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Addition of Amine Derivatives

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2:57 minutes

Problem 33a,b

Textbook Question

What are the products of the following reactions? (A trace amount of acid is present in each case.)
a. cyclopentanone + ethylamine
b. cyclopentanone + diethylamine

Verified step by step guidance

Identify the type of reaction occurring in each case. Cyclopentanone is a ketone, and the presence of an amine (ethylamine or diethylamine) along with a trace amount of acid suggests that these are nucleophilic addition-elimination reactions, potentially forming imines or enamines.

For part (a), cyclopentanone reacts with ethylamine (a primary amine). The reaction mechanism involves the nucleophilic attack of the amine's nitrogen on the carbonyl carbon of cyclopentanone, forming a tetrahedral intermediate.

In the presence of a trace amount of acid, the intermediate undergoes protonation and dehydration (loss of water), leading to the formation of an imine. The general structure of the imine will be: \( \text{C}_5\text{H}_8=\text{N}-\text{CH}_2\text{CH}_3 \).

For part (b), cyclopentanone reacts with diethylamine (a secondary amine). Secondary amines cannot form imines because they lack a hydrogen atom on the nitrogen to facilitate dehydration. Instead, the reaction forms an enamine. The mechanism involves nucleophilic attack, followed by proton transfer and elimination of water, resulting in a compound with a double bond adjacent to the nitrogen atom.

The enamine product for part (b) will have the general structure: \( \text{C}_5\text{H}_7=\text{CH}-\text{N}(-\text{CH}_2\text{CH}_3)_2 \). This structure arises from the alpha-hydrogen of cyclopentanone being removed during the enamine formation process.

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Key Concepts

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

Nucleophilic Addition

Nucleophilic addition is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophilic carbon atom, typically found in carbonyl compounds like ketones and aldehydes. In the case of cyclopentanone reacting with amines, the nitrogen atom of the amine acts as the nucleophile, attacking the carbonyl carbon, leading to the formation of an intermediate that can further react to form an imine or amine product.

Acid-Base Catalysis

In the presence of a trace amount of acid, acid-base catalysis can facilitate the reaction between cyclopentanone and amines. The acid can protonate the carbonyl oxygen, increasing the electrophilicity of the carbonyl carbon, making it more susceptible to nucleophilic attack by the amine. This process can enhance the rate of reaction and influence the products formed.

Imine Formation

Imine formation is a specific reaction that occurs when a primary amine reacts with a carbonyl compound, resulting in the creation of an imine. In the reactions involving cyclopentanone and ethylamine or diethylamine, the nucleophilic attack leads to the formation of a tetrahedral intermediate, which can lose water to yield an imine. The nature of the amine can affect the stability and reactivity of the resulting imine.

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