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

12. Alcohols, Ethers, Epoxides and Thiols

Making Ethers - Alcohol Condensation

Organic Chemistry

12. Alcohols, Ethers, Epoxides and Thiols

Making Ethers - Alcohol Condensation

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6:15 minutes

Problem 12

Textbook Question

Propose a mechanism for the acid-catalyzed condensation of n-propyl alcohol to n-propyl ether, as shown above. When the temperature is allowed to rise too high, propene is formed. Propose a mechanism for the formation of propene, and explain why it is favored at higher temperatures.

Verified step by step guidance

Step 1: Begin by understanding the acid-catalyzed condensation mechanism for the formation of n-propyl ether from n-propyl alcohol. The process typically involves protonation of the alcohol to form a good leaving group.

Step 2: Protonation of n-propyl alcohol occurs when the alcohol oxygen atom donates a pair of electrons to a hydrogen ion (H⁺) from the acid catalyst, forming an oxonium ion. This is represented as:

{CH}_{3} {CH}_{2} {CH}_{2} - OH + H + \to {CH}_{3} {CH}_{2} {CH}_{2} - OH +

Step 3: The oxonium ion can then undergo nucleophilic attack by another molecule of n-propyl alcohol, leading to the formation of n-propyl ether. This step involves the displacement of water as a leaving group, forming the ether linkage.

Step 4: For the formation of propene at higher temperatures, consider the elimination mechanism. The oxonium ion can lose a water molecule, forming a carbocation intermediate. This is followed by a deprotonation step, where a hydrogen ion is removed from the adjacent carbon, resulting in the formation of propene. This is represented as:

{CH}_{3} {CH}_{2} {CH}_{2} - OH + \to {CH}_{3} {CH}_{2} - CH + \to {CH}_{3} CH = CH 2

Step 5: Explain why propene formation is favored at higher temperatures. The elimination reaction leading to propene is an endothermic process, which means it requires heat to proceed. At higher temperatures, the energy barrier for elimination is overcome more easily, favoring the formation of propene over the condensation reaction.

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Key Concepts

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

Acid-Catalyzed Condensation

Acid-catalyzed condensation is a reaction where an acid facilitates the formation of an ether from alcohols by promoting the nucleophilic attack of an alcohol on another alcohol molecule. The acid protonates the hydroxyl group, making it a better leaving group, which allows for the formation of a new C-O bond and the release of water. This process is crucial for understanding how n-propyl alcohol can be converted into n-propyl ether.

Elimination Reaction

An elimination reaction involves the removal of a small molecule from a larger one, resulting in the formation of a double bond. In the context of n-propyl alcohol, when the temperature increases, the reaction can shift towards elimination, leading to the formation of propene. This occurs because higher temperatures favor the formation of products with greater entropy, such as alkenes, over the more stable ether.

Le Chatelier's Principle

Le Chatelier's Principle states that if a system at equilibrium is disturbed, the system will adjust to counteract the disturbance and restore a new equilibrium. In the case of the acid-catalyzed condensation and subsequent elimination reactions, increasing the temperature shifts the equilibrium towards the formation of propene, as the system seeks to minimize the effect of the added heat by favoring the endothermic elimination process.

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Related Practice

Textbook Question

Which of the following ethers can be formed in good yield by condensation of the corresponding alcohols? For those that cannot be formed by condensation, suggest an alternative method that will work.

(a) dibutyl ether

(b) ethyl n-propyl ether

Textbook Question

1,4-Dioxane is made commercially by the acid-catalyzed condensation of an alcohol.

(a) Show what alcohol will undergo condensation, with loss of water, to give 1,4-dioxane.

(b) Propose a mechanism for this reaction.

Textbook Question

Contrast the mechanisms of the two preceding reactions, the dehydration and condensation of ethanol.

Textbook Question

Explain why bimolecular condensation is a poor method for making unsymmetrical ethers such as ethyl methyl ether.

Textbook Question

Propose a mechanism for each of the following reactions:

Textbook Question

Heating an alcohol with sulfuric acid is a good way to prepare a symmetrical ether such as diethyl ether.

b. How would you synthesize ethyl propyl ether?

Textbook Question

Propose a mechanism for each of the following reactions:

Textbook Question

Heating an alcohol with sulfuric acid is a good way to prepare a symmetrical ether such as diethyl ether.

a. Explain why it is not a good way to prepare an unsymmetrical ether such as ethyl propyl ether.

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