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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1:39 minutes

Problem 45c

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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Identify the reactants in the acetylide alkylation reaction. Acetylide ions are strong nucleophiles formed by deprotonating terminal alkynes with a strong base, such as NaNH₂. The alkyl halide provides the electrophile for the reaction.

Determine the structure of the acetylide ion. The acetylide ion is formed by removing the terminal hydrogen from the alkyne, leaving a negatively charged carbon triple-bonded to another carbon.

Analyze the alkyl halide used in the reaction. The alkyl halide should be a primary or methyl halide to avoid side reactions such as elimination. Secondary or tertiary alkyl halides are less suitable for this reaction.

Write the mechanism of the reaction. The acetylide ion attacks the carbon atom of the alkyl halide in an SN2 reaction, displacing the halide ion (leaving group) and forming a new carbon-carbon bond.

Combine the acetylide ion and the alkyl group from the alkyl halide to determine the product. Ensure the product has the correct number of carbons by adding the carbons from the acetylide ion and the alkyl halide together.

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Key Concepts

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

Acetylide Ions

Acetylide ions are negatively charged species formed by deprotonating terminal alkynes. They are strong nucleophiles, capable of attacking electrophiles in nucleophilic substitution reactions. Understanding their formation and reactivity is crucial for predicting the products of alkylation reactions.

Alkylation Reactions

Alkylation reactions involve the transfer of an alkyl group from one molecule to another, typically through nucleophilic substitution. In the context of acetylide alkylation, the acetylide ion attacks a primary alkyl halide, resulting in the formation of a new carbon-carbon bond. This process is essential for building larger carbon skeletons in organic synthesis.

Carbon Count in Products

Maintaining the correct number of carbons in the product is vital in organic chemistry. When performing acetylide alkylation, the total number of carbon atoms in the starting materials must equal the total in the products. This concept ensures that the reaction adheres to the law of conservation of mass and helps in verifying the accuracy of the proposed products.

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Related Practice

Textbook Question

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

i. sodium amide

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

Ethinylestradiol is a synthetic hormone mimic used as a contraceptive for its ability to prevent ovulation. Suggest a mechanism for the synthesis using sodium acetylide and estrone, followed by quenching with acid.

Textbook Question

Predict the product of the following acetylide alkylations.

(a)

Textbook Question

Predict the product of the following acetylide alkylations.

(c)

Textbook Question

Suggest reagents you might use to generate the product from the given reactant.

(a)

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