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

9. Alkenes and Alkynes

Hydrogenation of Alkynes

Organic Chemistry

9. Alkenes and Alkynes

Hydrogenation of Alkynes

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4:40 minutes

Problem 29

Textbook Question

Sodium amide, the base we use to deprotonate terminal alkynes, is synthesized by reducing ammonia via a mechanism similar to the reduction of alkynes in Figure 10.21. Suggest a mechanism for this reaction.

Verified step by step guidance

Step 1: Begin by recognizing that sodium amide (NaNH₂) is formed by the reaction of ammonia (NH₃) with metallic sodium (Na⁰). The reaction also produces hydrogen gas (H₂) as a byproduct.

Step 2: Understand that metallic sodium (Na⁰) acts as a reducing agent. Sodium donates an electron to ammonia, initiating the formation of a radical intermediate. This is similar to the reduction mechanism seen in alkynes.

Step 3: Propose the first step of the mechanism: Sodium donates an electron to ammonia (NH₃), forming an ammonia radical anion (NH₃⁻•). This radical anion is highly reactive.

Step 4: The ammonia radical anion (NH₃⁻•) undergoes proton transfer, where it loses a proton to form the amide ion (NH₂⁻) and hydrogen gas (H₂). This step is facilitated by the presence of another ammonia molecule acting as a proton donor.

Step 5: Finally, the amide ion (NH₂⁻) combines with sodium cation (Na⁺) to form sodium amide (NaNH₂). This process repeats for the second ammonia molecule, resulting in the overall reaction: 2 NH₃ + 2 Na⁰ → 2 NaNH₂ + H₂.

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Key Concepts

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

Deprotonation of Terminal Alkynes

Deprotonation of terminal alkynes involves the removal of a proton from the terminal carbon atom, resulting in the formation of an alkyne anion. This process is typically facilitated by strong bases like sodium amide (NaNH₂), which can effectively abstract the acidic hydrogen due to the high acidity of terminal alkynes compared to other hydrocarbons.

Reduction Mechanisms

Reduction mechanisms in organic chemistry refer to the processes that involve the gain of electrons or hydrogen, or the loss of oxygen. In the context of synthesizing sodium amide from ammonia, the reduction of ammonia involves the transfer of electrons from sodium metal to ammonia, resulting in the formation of sodium amide and hydrogen gas.

Sodium Amide Synthesis

Sodium amide (NaNH₂) is synthesized through the reduction of ammonia (NH₃) using sodium metal (Na). This reaction is significant in organic synthesis as sodium amide serves as a strong base for deprotonating terminal alkynes, enabling further reactions such as nucleophilic substitutions or eliminations in organic synthesis.

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