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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3:20 minutes

Problem 54c

Textbook Question

Predict the products formed when cyclohexanecarbaldehyde reacts with the following reagents.
(c) semicarbazide and weak acid

Verified step by step guidance

Identify the functional group in cyclohexanecarbaldehyde. The molecule contains an aldehyde group (-CHO) attached to a cyclohexane ring.

Understand the role of semicarbazide in the reaction. Semicarbazide is a derivative of hydrazine (NH2-NH2) and reacts with aldehydes or ketones to form semicarbazones. This reaction is a nucleophilic addition-elimination process.

Recognize the role of the weak acid. The weak acid provides a mildly acidic environment, which helps to protonate the carbonyl oxygen of the aldehyde, making the carbonyl carbon more electrophilic and susceptible to nucleophilic attack by semicarbazide.

Write the reaction mechanism: (1) The lone pair on the nitrogen atom of semicarbazide attacks the electrophilic carbonyl carbon of the aldehyde, forming a tetrahedral intermediate. (2) Proton transfer occurs, facilitated by the weak acid, leading to the elimination of water and the formation of a double bond between the carbon and nitrogen.

Conclude that the product of the reaction is a semicarbazone, specifically cyclohexanecarbaldehyde semicarbazone, where the aldehyde group has been converted into a C=N-NH-CO-NH2 functional group.

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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 mechanism in organic chemistry where a nucleophile attacks an electrophilic carbon atom, typically found in carbonyl groups. In the case of cyclohexanecarbaldehyde, the carbonyl carbon is susceptible to attack by nucleophiles, such as semicarbazide, leading to the formation of a new bond and the eventual production of a corresponding addition product.

Formation of Hydrazones and Semicarbazones

Semicarbazide reacts with aldehydes and ketones to form semicarbazones, which are characterized by the presence of a C=N bond. This reaction is significant in organic synthesis and analytical chemistry, as semicarbazones can be used to identify and characterize carbonyl compounds. The reaction typically occurs under mild acidic conditions, facilitating the nucleophilic attack on the carbonyl carbon.

Acid-Base Catalysis

Acid-base catalysis involves the use of an acid or a base to enhance the rate of a chemical reaction. In the context of the reaction between cyclohexanecarbaldehyde and semicarbazide, a weak acid can help protonate the carbonyl oxygen, increasing the electrophilicity of the carbonyl carbon. This makes it more susceptible to nucleophilic attack, thereby promoting the formation of the semicarbazone product.

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