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

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Enamine Alkylation and Acylation

Organic Chemistry

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Enamine Alkylation and Acylation

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6:50 minutes

Problem 17a

Textbook Question

Describe how the following compounds could be prepared from cyclohexanone using an enamine intermediate:
a.

Verified step by step guidance

Step 1: Begin with cyclohexanone as the starting material. Cyclohexanone is a six-membered cyclic ketone with a carbonyl group (C=O).

Step 2: React cyclohexanone with a secondary amine (e.g., pyrrolidine) and a catalytic amount of an acid to form an enamine intermediate. The enamine is formed by the condensation of the ketone with the amine, where the carbonyl oxygen is replaced by a nitrogen group, and a double bond forms between the alpha-carbon and the adjacent carbon.

Step 3: Perform an alkylation reaction on the enamine intermediate. Treat the enamine with an alkyl halide (e.g., 1-bromobutane) to introduce the butyl group at the alpha-carbon of the cyclohexanone. The enamine acts as a nucleophile, attacking the electrophilic carbon of the alkyl halide, leading to the substitution of the halide with the butyl group.

Step 4: Hydrolyze the alkylated enamine back to the ketone. This is achieved by treating the product with aqueous acid, which regenerates the carbonyl group and removes the amine, yielding the desired alkylated ketone.

Step 5: Verify the structure of the final product. The product should be 2-butylcyclohexanone, where the butyl group is attached to the alpha-carbon of the cyclohexanone ring.

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Key Concepts

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

Enamine Chemistry

Enamines are formed by the reaction of a carbonyl compound, like cyclohexanone, with a secondary amine. This reaction involves the nucleophilic attack of the amine on the carbonyl carbon, followed by dehydration to yield the enamine. Enamines serve as versatile intermediates in organic synthesis, allowing for the formation of various products through electrophilic addition reactions.

Cyclohexanone Structure and Reactivity

Cyclohexanone is a cyclic ketone with a six-membered carbon ring and a carbonyl group (C=O). Its structure makes it a good candidate for enamine formation due to the stability of the resulting enamine. The reactivity of cyclohexanone allows it to undergo various transformations, including nucleophilic additions and substitutions, which are essential for synthesizing different compounds.

Synthetic Pathways in Organic Chemistry

Synthetic pathways refer to the series of chemical reactions that transform starting materials into desired products. Understanding these pathways is crucial for predicting how to prepare specific compounds from intermediates like enamines. In this context, the ability to manipulate reaction conditions and select appropriate reagents is key to achieving the desired transformations from cyclohexanone.

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Related Practice

Textbook Question

Describe how the following compounds could be prepared from cyclohexanone using an enamine intermediate:

Textbook Question

Write equations showing the expected products of the following enamine alkylation and acylation reactions. Then give the final products expected after hydrolysis of the iminium salts.

(a) pyrrolidine enamine of pentan-3-one + allyl chloride

(b) pyrrolidine enamine of acetophenone + butanoyl chloride

Textbook Question

Without looking back, propose a mechanism for the hydrolysis of this iminium salt to the alkylated ketone. The first step is attack by water, followed by loss of a proton to give a carbinolamine. Protonation on nitrogen allows pyrrolidine to leave, giving the protonated ketone.

Textbook Question

Write equations showing the expected products of the following enamine alkylation and acylation reactions. Then give the final products expected after hydrolysis of the iminium salts.

Textbook Question

What reagents should be used to prepare the following compounds?

Textbook Question

Show how you would accomplish each conversion using an enamine synthesis with pyrrolidine as the secondary amine.

(c)

Textbook Question

Predict the products of the following reactions.

(e)

Multiple Choice

Provide the major product after each step for the following reaction.

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