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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2:27 minutes

Problem 77e

Textbook Question

The acid-catalyzed hydration we learned here in Chapter 8 is reversible:

(e) How might you shift the equilibrium to the left?

Verified step by step guidance

Understand the acid-catalyzed hydration reaction: This reaction involves the addition of water (H₂O) to an alkene in the presence of an acid catalyst, forming an alcohol. The reaction is reversible, meaning the alcohol can revert back to the alkene and water under certain conditions.

Recall Le Chatelier's Principle: This principle states that if a dynamic equilibrium is disturbed by changing the conditions, the system will adjust to counteract the disturbance and restore equilibrium. To shift the equilibrium to the left (favoring the formation of the alkene and water), you need to manipulate the reaction conditions.

Decrease the concentration of water: Since water is a reactant in the forward reaction, reducing its concentration will drive the equilibrium toward the reactants (alkene and water). This can be achieved by removing water from the reaction mixture or using a drying agent.

Increase the concentration of the alcohol: Adding more alcohol to the system will push the equilibrium toward the reactants (alkene and water), as the system tries to counteract the increase in alcohol concentration.

Change the temperature: Acid-catalyzed hydration is typically exothermic in the forward direction. Lowering the temperature can favor the reverse reaction (formation of alkene and water), as the system compensates for the removal of heat.

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Key Concepts

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

Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change. In the context of acid-catalyzed hydration, altering concentration, temperature, or pressure can influence the direction of the reaction, allowing us to predict how to shift the equilibrium to favor either the reactants or products.

Acid-Catalyzed Hydration

Acid-catalyzed hydration is a reaction where an alkene reacts with water in the presence of an acid to form an alcohol. This process involves the formation of a carbocation intermediate and is reversible, meaning that the products can revert back to the reactants under certain conditions. Understanding this reaction is crucial for manipulating the equilibrium.

Equilibrium Constant (K)

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a reversible reaction. A change in concentration of either reactants or products will affect the value of K, thus shifting the equilibrium position. By manipulating concentrations, one can effectively shift the equilibrium to the left, favoring the formation of reactants.

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Related Practice

Textbook Question

Propose mechanisms for the following reactions.

(a)

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.

(b)

Textbook Question

The acid-catalyzed hydration we learned here in Chapter 8 is reversible.

(a) Propose a mechanism for the formation of an alkene from an alcohol.

Textbook Question

The acid-catalyzed hydration we learned here in Chapter 8 is reversible:

(d) How might you shift the equilibrium to the right?

Textbook Question

If the compound shown in the margin is heated in the presence of H₂SO₄,

a. what constitutional isomer would be formed in greatest yield?

b. what stereoisomer would be formed in greater yield?

Textbook Question

Starting from bromobenzene and any other reagents and solvents you need, show how you would synthesize the following compounds. Any of these products may be used as starting materials in subsequent parts of this problem.

c. 1-phenylpropan-2-ol

Textbook Question

Explain why the acid-catalyzed dehydration of an alcohol is a reversible reaction, whereas the base-promoted dehydrohalogenation of an alkyl halide is an irreversible reaction.

Textbook Question

What stereoisomers are formed in the following reactions? Which stereoisomer is the major product?

a. the acid-catalyzed dehydration of 1-pentanol to 2-pentene

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