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

10. Addition Reactions

Alkyne Hydration

Organic Chemistry

10. Addition Reactions

Alkyne Hydration

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5:24 minutes

Problem 40e

Textbook Question

Answer Problem 39, parts a–h, using 2-butyne as the starting material instead of propyne.
e. aqueous H₂SO₄, HgSO₄

Verified step by step guidance

Identify the starting material: The starting material is 2-butyne, which is an alkyne with the structure CH3-C≡C-CH3.

Understand the reaction conditions: The reagents are aqueous H2SO4 (sulfuric acid) and HgSO4 (mercuric sulfate). This combination is used to catalyze the hydration of alkynes, leading to the formation of a ketone via Markovnikov addition of water.

Determine the mechanism: The reaction proceeds through the formation of an enol intermediate (a compound with a hydroxyl group attached to a carbon-carbon double bond). This enol undergoes tautomerization to form a ketone, which is the more stable product.

Apply Markovnikov's rule: In the hydration of 2-butyne, the OH group from water will add to the more substituted carbon of the triple bond, while the hydrogen will add to the less substituted carbon. This ensures the formation of the more stable ketone.

Write the product structure: The final product will be a ketone, specifically 2-butanone (CH3-CO-CH2-CH3), as the triple bond in 2-butyne is converted into a carbonyl group at the more substituted carbon.

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Key Concepts

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

Hydration of Alkynes

The hydration of alkynes involves the addition of water across the triple bond, typically in the presence of an acid catalyst. In this case, 2-butyne reacts with aqueous H2SO4 to form an enol, which subsequently tautomerizes to a ketone. Understanding this process is crucial for predicting the products of the reaction.

Markovnikov's Rule

Markovnikov's Rule states that in the addition of HX to an alkene or alkyne, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This principle helps determine the regioselectivity of the hydration reaction, guiding the formation of the more stable carbocation intermediate during the reaction with 2-butyne.

Tautomerization

Tautomerization is a chemical reaction that involves the rearrangement of bonds within a compound, resulting in the interconversion between two isomers, typically a keto and an enol form. In the context of the hydration of 2-butyne, the initial enol formed from the reaction with H2SO4 will quickly convert to the more stable ketone, which is the final product of the reaction.

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Related Practice

Textbook Question

Hydration of alkynes (via oxymercuration) gives good yields of single compounds only with symmetrical or terminal alkynes. Show what the products would be from hydration of each compound.

e. 3-methylcyclodecyne

Textbook Question

Hydration of alkynes (via oxymercuration) gives good yields of single compounds only with symmetrical or terminal alkynes. Show what the products would be from hydration of each compound.

c. hex-1-yne

Textbook Question

What reagents should be used to carry out the following syntheses?

Textbook Question

For each of the following ketones/aldehydes, indicate whether it is possible to synthesize it from an alkyne as the only compound in good ( > 50%) yield. If so, how would you do it?

(a)

Textbook Question

How can the following compounds be synthesized, starting with a hydrocarbon that has the same number of carbons as the desired product?

Multiple Choice

Predict the major, organic product for the following reaction.

Textbook Question

Only one alkyne forms an aldehyde when it undergoes the mercuric-ion-catalyzed addition of water. Identify the alkyne.

Textbook Question

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

h. hex-1-yne → hexan-2-one, CH₃COCH₂CH₂CH₂CH₃

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Answer Problem 39, parts a–h, using 2-butyne as the starting material instead of propyne. e. aqueous H2SO4, HgSO4

Key Concepts

Hydration of Alkynes

Markovnikov's Rule

Tautomerization

Watch next

Answer Problem 39, parts a–h, using 2-butyne as the starting material instead of propyne.
e. aqueous H₂SO₄, HgSO₄