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

Imine vs Enamine

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Imine vs Enamine

Previous problemNext problem

3:20 minutes

Problem 49e

Textbook Question

Propose mechanisms for the following reactions.
(e)

Verified step by step guidance

Step 1: Recognize the reaction type. This is an intramolecular cyclization reaction involving the formation of a cyclic imine (a six-membered ring) from an amino ketone under acidic conditions.

Step 2: Protonation of the carbonyl group. Under acidic conditions, the oxygen atom of the ketone group is protonated, increasing the electrophilicity of the carbonyl carbon and making it more susceptible to nucleophilic attack.

Step 3: Nucleophilic attack by the amine group. The lone pair of electrons on the nitrogen atom of the amine group attacks the electrophilic carbonyl carbon, forming a tetrahedral intermediate.

Step 4: Elimination of water. The intermediate undergoes dehydration (loss of a water molecule), leading to the formation of a double bond between the carbon and nitrogen atoms.

Step 5: Formation of the cyclic imine. The reaction completes with the formation of a six-membered ring structure containing a double bond between the carbon and nitrogen atoms, stabilized under acidic conditions.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Aldehyde Reactivity

Aldehydes are highly reactive carbonyl compounds characterized by the presence of a carbonyl group (C=O) bonded to at least one hydrogen atom. This reactivity allows them to undergo nucleophilic addition reactions, where nucleophiles, such as amines, can attack the electrophilic carbon of the carbonyl, leading to the formation of various products, including imines.

Imine Formation

Imine formation occurs when a primary amine reacts with an aldehyde or ketone, resulting in the condensation of the amine and carbonyl compound. This reaction typically involves the nucleophilic attack of the amine on the carbonyl carbon, followed by the elimination of water. The resulting imine features a carbon-nitrogen double bond (C=N), which is a key functional group in organic chemistry.

Protonation and Equilibrium

Protonation refers to the addition of a proton (H+) to a molecule, which can enhance the electrophilicity of the carbonyl carbon in aldehydes. In the context of imine formation, protonation of the carbonyl oxygen increases the positive charge on the carbon, making it more susceptible to nucleophilic attack by the amine. Understanding the role of protonation is crucial for predicting the direction of the reaction and the stability of intermediates.

Watch next

Master General Reactions with a bite sized video explanation from Johnny

Start learning