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

14. Synthetic Techniques

Alkynide Alkylation

Organic Chemistry

14. Synthetic Techniques

Alkynide Alkylation

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Problem 83

Textbook Question

Reaction of the acetylide with the epoxide shown will not form the desired product. What side reaction occurs instead? Why?

Verified step by step guidance

Step 1: Understand the reactivity of acetylides. Acetylides are strong nucleophiles due to the negative charge on the carbon atom. They are also strong bases, which can lead to side reactions in the presence of acidic or proton-donating groups.

Step 2: Analyze the structure of the epoxide. Epoxides are three-membered cyclic ethers with significant ring strain, making them susceptible to nucleophilic attack. However, the reaction conditions and the nature of the nucleophile can influence the outcome.

Step 3: Consider the basicity of the acetylide. As a strong base, the acetylide can abstract a proton from any available acidic hydrogen in the reaction mixture, such as from water, alcohols, or other proton sources, instead of attacking the epoxide.

Step 4: Evaluate the competition between nucleophilic attack and proton abstraction. If proton abstraction occurs, the acetylide is converted into a neutral alkyne, which is no longer nucleophilic and cannot react with the epoxide to form the desired product.

Step 5: Conclude the side reaction. The side reaction involves the acetylide acting as a base and abstracting a proton, leading to the formation of an alkyne and preventing the desired nucleophilic attack on the epoxide.

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Key Concepts

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

Acetylide Nucleophiles

Acetylide ions are strong nucleophiles derived from terminal alkynes. They can attack electrophilic centers, such as carbon atoms in epoxides, leading to nucleophilic substitution reactions. However, their reactivity can also lead to side reactions, especially when the electrophile is sterically hindered or reactive in other ways.

Epoxide Reactivity

Epoxides are three-membered cyclic ethers that are highly reactive due to the strain in their ring structure. They can undergo nucleophilic attack at the less hindered carbon atom, but if steric hindrance or other factors are present, the reaction may not proceed as expected. Understanding the regioselectivity of epoxide reactions is crucial for predicting the outcome of reactions involving acetylides.

Side Reactions in Organic Chemistry

Side reactions are unintended reactions that occur alongside the desired reaction, often leading to byproducts. In the case of acetylide and epoxide reactions, side reactions can occur due to the formation of more stable intermediates or competing pathways, such as ring-opening of the epoxide by other nucleophiles or elimination reactions. Recognizing these possibilities is essential for predicting reaction outcomes.

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Related Practice

Textbook Question

Predict the products formed when CH₃CH₂–C≡C:^–Na⁺ reacts with the following compounds.

(d) cyclohexanone

(e) CH₃CH₂CH₂CHO

Textbook Question

The application box in the margin of states, “The addition of an acetylide ion to a carbonyl group is used in the synthesis of ethchlorvynol, a drug used to cause drowsiness and induce sleep.” Show how you would accomplish this synthesis from acetylene and a carbonyl compound.

Textbook Question

Show how the following compounds can be prepared, using ethyne as one of the starting materials:

1. 1-pentyn-3-ol

Textbook Question

How could the following compounds be synthesized from acetylene?

Textbook Question

Beginning with the molecules on the left of each chemical equation, synthesize the molecules shown. While there can be multiple ways of doing each synthesis, the minimum number of steps necessary is indicated over each reaction arrow.

(b)

Textbook Question

Beginning with the molecules on the left, provide a synthesis of the molecule on the right. The ideal number of steps is indicated over the reaction arrow, although there may be alternate routes worth considering.

(b)

Textbook Question

Synthesize the following molecules beginning with only organic molecules containing three carbons or fewer.

(b)

Textbook Question

Synthesize the following molecules beginning with only organic molecules containing three carbons or fewer.

(e)

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