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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 41a
Chapter 14, Problem 41a

Both LiAlH4 and Grignard reagents react with carbonyl compounds to give alkoxide ion intermediates (that become protonated in an aqueous workup). Those alkoxides can react with 1° or methyl alkyl halides or tosylates to give ethers. Show how the following ethers can be formed in this two-step process. As starting materials you may use any reactants containing 7 carbons or fewer.
(a) Chemical structure of an ether featuring a central oxygen atom bonded to two carbon chains, each with aromatic rings.

Verified step by step guidance
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Step 1: Analyze the target ether structure. The ether shown has a phenyl group (benzene ring) attached to one side of the oxygen atom and an allyl group (CH2=CH-CH2-) attached to the other side. This suggests that the synthesis involves combining a phenol derivative and an allyl halide or tosylate.
Step 2: Choose the starting materials. To form the phenyl group attached to the oxygen, start with phenol (C6H5OH). For the allyl group, use allyl bromide (CH2=CH-CH2Br) or allyl tosylate as the alkylating agent.
Step 3: Perform the first step of the reaction. React phenol with a base, such as NaH or KOH, to deprotonate the hydroxyl group and form the phenoxide ion (C6H5O⁻). This step prepares the phenol for nucleophilic substitution.
Step 4: Perform the second step of the reaction. React the phenoxide ion with allyl bromide or allyl tosylate in an SN2 reaction. The phenoxide ion acts as a nucleophile, attacking the electrophilic carbon in the allyl halide or tosylate, displacing the leaving group (Br⁻ or tosylate) and forming the ether bond.
Step 5: Verify the product. The reaction yields the desired ether, where the phenyl group is bonded to the oxygen atom, and the allyl group is bonded to the other side of the oxygen atom. Ensure that the starting materials used contain 7 carbons or fewer, as specified in the problem.

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Key Concepts

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

Reduction of Carbonyl Compounds

LiAlH4 (Lithium aluminum hydride) and Grignard reagents are powerful reducing agents that react with carbonyl compounds to form alkoxide intermediates. In this process, the carbonyl group (C=O) is converted to an alcohol (R-OH) by the addition of hydride ions, which is crucial for the subsequent formation of ethers.
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Formation of Ethers via Alkoxide Reaction

Once alkoxide ions are formed from the reduction of carbonyl compounds, they can react with primary (1°) or methyl alkyl halides or tosylates. This nucleophilic substitution reaction leads to the formation of ethers, where the alkoxide acts as a nucleophile, attacking the electrophilic carbon of the alkyl halide.
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Aqueous Workup

After the reaction involving alkoxides, an aqueous workup is typically performed to protonate the alkoxide, converting it into an alcohol. This step is essential for isolating the desired ether product, as it ensures that the reaction conditions are neutralized and any unreacted reagents are removed.
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Related Practice
Textbook Question

The following reaction resembles the acid-catalyzed cyclization of squalene oxide. Propose a mechanism for this reaction.

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Textbook Question

Both LiAlH4 and Grignard reagents react with carbonyl compounds to give alkoxide ion intermediates (that become protonated in an aqueous workup). Those alkoxides can react with 1° or methyl alkyl halides or tosylates to give ethers. Show how the following ethers can be formed in this two-step process. As starting materials you may use any reactants containing 7 carbons or fewer.

(b)

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Textbook Question

Both LiAlH4 and Grignard reagents react with carbonyl compounds to give alkoxide ion intermediates (that become protonated in an aqueous workup). Those alkoxides can react with 1° or methyl alkyl halides or tosylates to give ethers. Show how the following ethers can be formed in this two-step process. As starting materials you may use any reactants containing 7 carbons or fewer.

(c)

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Textbook Question

(a) Show how you would synthesize the pure (R) enantiomer of 2-butyl methyl sulfide, starting with pure (R)-butan-2-ol and any reagents you need

(b) Show how you would synthesize the pure (S) enantiomer of the product, still starting with (R)-butan-2-ol and any reagents you need.

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Textbook Question

Give the structures of intermediates A through H in the following synthesis of trans-1-cyclohexyl-2-methoxycyclohexane.

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Textbook Question

Show how you would convert hex-1-ene to each of the following compounds. You may use any additional reagents and solvents you need.

(a) 2-methoxyhexane

(b) 1-methoxyhexane

(c) 1-methoxyhexan-2-ol

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