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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4:05 minutes

Problem 22d,e

Textbook Question

Predict the products of the sulfuric acid-catalyzed dehydration of the following alcohols. When more than one product is expected, label the major and minor products.
(d) 1-isopropylcyclohexanol
(e) 2-methylcyclohexanol

Verified step by step guidance

Step 1: Understand the reaction mechanism. Sulfuric acid-catalyzed dehydration of alcohols typically proceeds via an E1 mechanism for secondary and tertiary alcohols. The reaction involves protonation of the hydroxyl group, formation of a carbocation intermediate, and elimination of water to form an alkene.

Step 2: Analyze the structure of the alcohols. For (d) 1-isopropylcyclohexanol, the hydroxyl group is attached to a secondary carbon. For (e) 2-methylcyclohexanol, the hydroxyl group is also attached to a secondary carbon. Both alcohols will form carbocations upon dehydration.

Step 3: Consider carbocation stability. In (d), the carbocation formed after dehydration will be influenced by the isopropyl group, which provides hyperconjugation and inductive effects to stabilize the carbocation. In (e), the carbocation formed will be stabilized by the methyl group through similar effects.

Step 4: Predict the possible alkenes. For (d), elimination of a proton from adjacent carbons to the carbocation will yield different alkenes. Apply Zaitsev's rule, which states that the more substituted alkene is the major product. For (e), follow the same process to predict the alkenes and identify the major and minor products.

Step 5: Label the major and minor products. Based on Zaitsev's rule, the major product will be the more substituted alkene, while the minor product will be the less substituted alkene. Consider steric and electronic factors to finalize the labeling of major and minor products for both (d) and (e).

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Key Concepts

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

Dehydration of Alcohols

Dehydration of alcohols is a chemical reaction where an alcohol loses a water molecule, typically in the presence of an acid catalyst like sulfuric acid. This process often leads to the formation of alkenes. The reaction can proceed via either an E1 or E2 mechanism, depending on the structure of the alcohol and the reaction conditions, influencing the regioselectivity of the products.

Regioselectivity

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others when multiple products are possible. In the dehydration of alcohols, the more stable alkene (often the more substituted one) is typically formed as the major product due to greater stability from hyperconjugation and alkyl substitution, while less stable isomers are considered minor products.

Carbocation Stability

Carbocation stability is a key factor in determining the outcome of dehydration reactions. Carbocations are positively charged carbon species that can form during the reaction. Their stability increases with the degree of substitution: tertiary carbocations are more stable than secondary, which are more stable than primary. This stability influences which alkene product is favored in the dehydration process.

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Related Practice

Textbook Question

Write a balanced equation for each reaction, showing the major product you expect.

(a)

Textbook Question

Write a balanced equation for each reaction, showing the major product you expect.

(c)

Textbook Question

Show the product(s) you expect from dehydration of the following alcohols when they are heated in sulfuric or phosphoric acid. In each case, use a mechanism to show how the products are formed.

(c)

Textbook Question

Write a mechanism that explains the formation of the following product. In your mechanism, explain the cause of the rearrangement, and explain the failure to form the Zaitsev product.

Textbook Question

Propose mechanisms for the following reactions. Additional products may be formed, but your mechanism only needs to explain the products shown.

(b)

Textbook Question

Four pairs of compounds are shown. In each pair, one of the compounds reacts more quickly, or with a more favorable equilibrium constant, than the less conjugated system. In each case, explain the enhanced reactivity.

(c)

Textbook Question

Predict the product of the following pinacol rearrangements.

(b)

Textbook Question

Propose a mechanism for each of the following reactions:

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