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Ch. 14 - Ethers, Epoxides, and Thioethers
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh. 14 - Ethers, Epoxides, and ThioethersProblem 13
Chapter 14, Problem 13

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
(c) di-sec-butyl ether

Verified step by step guidance
1
Step 1: Understand the condensation reaction mechanism for forming ethers. This typically involves the acid-catalyzed dehydration of alcohols, where two alcohol molecules react to form an ether and water. This method works well for primary alcohols but is less effective for secondary and tertiary alcohols due to steric hindrance and competing elimination reactions.
Step 2: Analyze (a) dibutyl ether. Dibutyl ether can be formed by the condensation of two molecules of 1-butanol (a primary alcohol). Since primary alcohols undergo acid-catalyzed dehydration efficiently, dibutyl ether can be formed in good yield using this method.
Step 3: Analyze (b) ethyl n-propyl ether. This ether involves two different alcohols: ethanol (a primary alcohol) and 1-propanol (another primary alcohol). Acid-catalyzed condensation of two different alcohols often leads to a mixture of products due to the lack of selectivity. An alternative method, such as Williamson ether synthesis, would be more effective. In this method, ethanol can be converted to ethoxide (a strong nucleophile) and reacted with 1-propyl bromide or chloride to form ethyl n-propyl ether.
Step 4: Analyze (c) di-sec-butyl ether. Sec-butyl alcohol is a secondary alcohol, and secondary alcohols are prone to elimination reactions under acidic conditions, leading to the formation of alkenes instead of ethers. Acid-catalyzed condensation is not suitable for forming di-sec-butyl ether. An alternative method, such as Williamson ether synthesis, can be used. In this case, sec-butyl alcohol can be converted to sec-butoxide and reacted with sec-butyl bromide or chloride to form di-sec-butyl ether.
Step 5: Summarize the findings. Dibutyl ether can be formed in good yield by acid-catalyzed condensation of 1-butanol. Ethyl n-propyl ether and di-sec-butyl ether are better synthesized using the Williamson ether synthesis method due to limitations of the condensation reaction for mixed alcohols and secondary alcohols, respectively.

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Key Concepts

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

Ethers and Their Formation

Ethers are organic compounds characterized by an oxygen atom bonded to two alkyl or aryl groups. They can be formed through a condensation reaction between two alcohols, where water is eliminated. This process is known as the Williamson ether synthesis, which typically requires strong bases to deprotonate the alcohols and facilitate the nucleophilic attack.
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Condensation Reactions

Condensation reactions involve the combination of two molecules with the loss of a small molecule, often water. In the context of ether formation, this reaction occurs between alcohols, where the hydroxyl group of one alcohol reacts with the hydrogen of another, resulting in the formation of an ether and the release of water. The efficiency of this reaction can depend on steric factors and the nature of the alcohols involved.
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Steric Hindrance

Steric hindrance refers to the prevention of reactions due to the spatial arrangement of atoms within a molecule. In ether synthesis, bulky groups can hinder the approach of reactants, making certain ethers difficult to form via condensation. For example, secondary and tertiary alcohols are more sterically hindered than primary alcohols, which can affect the yield of the desired ether product.
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Related Practice
Textbook Question

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

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Textbook Question

Show how the following ethers might be synthesized using (1) alkoxymercuration–demercuration and (2) the Williamson synthesis. (When one of these methods cannot be used for the given ether, point out why it will not work.)

f. tert-butyl phenyl ether

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Textbook Question

Predict the products of the following reactions. An excess of acid is available in each case.

(c) anisole (methoxybenzene) + HBr

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Textbook Question

Propose a mechanism for the following reaction.

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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.

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Textbook Question

Predict the products of the following reactions. An excess of acid is available in each case.

(a) ethoxycyclohexane + HBr

(b) tetrahydropyran + HI

(c) anisole (methoxybenzene) + HBr

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