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

Acetylide

Organic Chemistry

9. Alkenes and Alkynes

Acetylide

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3:20 minutes

Problem 39i

Textbook Question

What is the major product of the reaction of 1 mol of propyne with each of the following reagents?
i. sodium amide

Verified step by step guidance

Step 1: Understand the structure of propyne. Propyne is an alkyne with the molecular formula C3H4. Its structure includes a triple bond between the first and second carbon atoms (CH≡C-CH3). The terminal hydrogen on the first carbon is acidic due to the sp hybridization of the carbon atom.

Step 2: Recognize the role of sodium amide (NaNH2) in the reaction. Sodium amide is a strong base that can deprotonate the acidic terminal hydrogen of propyne, forming a carbanion (acetylide ion). This reaction is a typical acid-base reaction.

Step 3: Write the chemical equation for the reaction. The reaction can be represented as: CH≡C-CH3 + NaNH2 → CH≡C⁻ + Na⁺ + NH3. Here, the acetylide ion (CH≡C⁻) is formed as the major product.

Step 4: Understand the significance of the acetylide ion. The acetylide ion is a nucleophile and can participate in further reactions, such as alkylation or addition reactions, depending on the reagents added subsequently.

Step 5: Note that no additional products are formed in this step unless further reagents are introduced. The major product of this reaction is the acetylide ion (CH≡C⁻), which is stabilized by the sodium cation (Na⁺).

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Key Concepts

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

Alkynes and Their Reactivity

Alkynes, such as propyne, are hydrocarbons containing at least one carbon-carbon triple bond. This triple bond makes alkynes more reactive than alkenes and alkanes, allowing them to undergo various reactions, including nucleophilic substitutions and eliminations. Understanding the reactivity of alkynes is crucial for predicting the products of their reactions with different reagents.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group by a nucleophile. In the case of propyne reacting with sodium amide (NaNH2), the amide ion acts as a strong nucleophile, attacking the terminal carbon of the alkyne. This reaction can lead to the formation of an alkyne anion, which can further react with electrophiles to form new products.

Formation of Alkynide Ions

When propyne reacts with sodium amide, it can generate an alkynide ion, which is a negatively charged species formed by deprotonation of the terminal hydrogen of the alkyne. This ion is highly reactive and can participate in further reactions, such as nucleophilic attacks on alkyl halides, leading to the formation of larger carbon chains. Recognizing the formation of alkynide ions is essential for predicting the major product of the reaction.

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Related Practice

Textbook Question

Suggest a method for synthesizing the following alkynes using an alkyne and an alkyl halide. [There are two correct answers for each product.]

(a)

Textbook Question

Show how you would accomplish the following synthetic transformations. Show all intermediates.

c. but-1-yne → oct-3-yne

Multiple Choice

Predict the major, organic product of the following reaction.

Textbook Question

What is the major product of the reaction of 1 mol of propyne with each of the following reagents?

j. the product of part i followed by 1-chloropropane

Textbook Question

Show how you might synthesize the following compounds, using acetylene and any suitable alkyl halides as your starting materials. If the compound given cannot be synthesized by this method, explain why.

a. hex-1-yne

b. hex-2-yne

c. hex-3-yne

Textbook Question

Give two sets of reactants (each set including an alkyl halide and a nucleophile) that could be used to synthesize the following alkyne:

CH₃CH₂C≡CCH₂CH₂CH₂CH₃

Textbook Question

Show the products of the following acetylide alkylation reactions. [Make sure your product has the correct number of carbons.]

(a)

Textbook Question

Show the products of the following acetylide alkylation reactions. [Make sure your product has the correct number of carbons.]

(c)

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What is the major product of the reaction of 1 mol of propyne with each of the following reagents? i. sodium amide

Key Concepts

Alkynes and Their Reactivity

Nucleophilic Substitution Reactions

Formation of Alkynide Ions

Watch next

What is the major product of the reaction of 1 mol of propyne with each of the following reagents?
i. sodium amide