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

Dehydration Reaction

Organic Chemistry

9. Alkenes and Alkynes

Dehydration Reaction

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7:01 minutes

Problem 94

Textbook Question

What product is obtained when the following vicinal diol is heated in an acidic solution?

Verified step by step guidance

Identify the functional group in the molecule: The given compound is a vicinal diol, which means it has two hydroxyl (-OH) groups on adjacent carbon atoms.

Recall the reaction mechanism: When a vicinal diol is heated in an acidic solution, it undergoes a pinacol rearrangement. This reaction involves the migration of a substituent group and the formation of a ketone or aldehyde.

Protonation of one hydroxyl group: In the acidic solution, one of the hydroxyl groups is protonated, making it a better leaving group. This step generates a carbocation intermediate after the loss of water (H₂O).

Analyze the carbocation stability: The carbocation formed will rearrange to stabilize itself. In this case, the migration of one of the cyclopentyl groups occurs to stabilize the carbocation, leading to a new intermediate structure.

Formation of the final product: After the rearrangement, a ketone is formed as the final product. The carbonyl group (C=O) will be located on the carbon atom that originally had the hydroxyl group.

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Key Concepts

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

Vicinal Diols

Vicinal diols, also known as glycols, are organic compounds that contain two hydroxyl (-OH) groups attached to adjacent carbon atoms. Their structure allows for unique reactivity, particularly under acidic conditions, where they can undergo dehydration to form more stable products. Understanding the structure and properties of vicinal diols is essential for predicting their behavior in chemical reactions.

Acid-Catalyzed Dehydration

Acid-catalyzed dehydration is a reaction where an alcohol or diol loses a water molecule in the presence of an acid, leading to the formation of alkenes or ethers. In the case of vicinal diols, heating in acidic conditions typically promotes the elimination of water, resulting in the formation of a more stable alkene. This process is crucial for understanding how diols can be transformed into other functional groups.

Carbocation Stability

Carbocation stability refers to the relative stability of positively charged carbon species that form during reactions such as dehydration. The stability of a carbocation is influenced by factors such as the degree of substitution (primary, secondary, tertiary) and resonance effects. Recognizing the stability of potential carbocations formed during the dehydration of vicinal diols is key to predicting the major product of the reaction.

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