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
(c) di-sec-butyl ether

Accepted Answer

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.

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

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Concetti chiave

Ethers and Their Formation

Condensation Reactions

Steric Hindrance

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