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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2:28 minutes

Problem 56e

Textbook Question

Indicate which alcohol in each pair undergoes an elimination reaction more rapidly when heated with H₂SO₄.
e.

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Identify the structure of each alcohol in the pair. Look for primary, secondary, or tertiary alcohols, as this will influence the rate of elimination.

Recall that elimination reactions of alcohols typically proceed via the E1 mechanism, especially when using a strong acid like H2SO4. In E1 reactions, the rate is influenced by the stability of the carbocation intermediate.

Determine the stability of the carbocation that would form from each alcohol. Tertiary carbocations are more stable than secondary, which are more stable than primary. The more stable the carbocation, the faster the elimination reaction.

Consider any additional factors that might influence carbocation stability, such as resonance or hyperconjugation. These can further stabilize the carbocation, increasing the rate of elimination.

Compare the alcohols in the pair based on the stability of their potential carbocations. The alcohol that forms the more stable carbocation will undergo elimination more rapidly when heated with H2SO4.

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Key Concepts

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

Elimination Reactions

Elimination reactions involve the removal of a small molecule from a larger one, typically resulting in the formation of a double bond. In organic chemistry, these reactions often occur with alcohols when treated with strong acids like H2SO4, leading to the formation of alkenes. The rate of elimination can depend on the structure of the alcohol, such as whether it is primary, secondary, or tertiary.

Alcohol Structure and Stability

The structure of the alcohol significantly influences its reactivity in elimination reactions. Tertiary alcohols are generally more reactive than secondary and primary alcohols due to the stability of the carbocation intermediate formed during the reaction. The more substituted the carbocation, the more stable it is, which facilitates a faster elimination process.

Role of H2SO4 in Dehydration

H2SO4 acts as a strong acid that protonates the alcohol, making it a better leaving group. This protonation step is crucial for the dehydration process, where water is eliminated to form an alkene. The presence of H2SO4 not only enhances the rate of elimination but also shifts the equilibrium towards the formation of the alkene product, especially under heat.

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Indicate which alcohol in each pair undergoes an elimination reaction more rapidly when heated with H₂SO₄.

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Explain why (S)-2-butanol forms a racemic mixture when it is heated in sulfuric acid.

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Propose a mechanism for the following reaction:

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What alkenes would you expect to be obtained from the acid-catalyzed dehydration of 1-hexanol?

Textbook Question

Indicate which alcohol in each pair undergoes an elimination reaction more rapidly when heated with H₂SO₄.

Textbook Question

Indicate which alcohol in each pair undergoes an elimination reaction more rapidly when heated with H₂SO₄.

Textbook Question

Propose mechanisms for the following reactions.

(b)

HINT: Alcohol dehydrations usually go through E1 elimination of the protonated alcohol, with a carbocation intermediate. Rearrangements are common.

Textbook Question

Propose mechanisms for the following reactions.

HINT: Alcohol dehydrations usually go through E1 elimination of the protonated alcohol, with a carbocation intermediate. Rearrangements are common.

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Indicate which alcohol in each pair undergoes an elimination reaction more rapidly when heated with H2SO4.e.

Key Concepts

Elimination Reactions

Alcohol Structure and Stability

Role of H2SO4 in Dehydration

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Indicate which alcohol in each pair undergoes an elimination reaction more rapidly when heated with H₂SO₄.
e.