The Williamson ether synthesis involves the displacement of an alkyl halide or tosylate by an alkoxide ion. Would the synthesis shown be possible by making a tosylate and displacing it? If so, show the sequence of reactions. If not, explain why not and show an alternative synthesis that would be more likely to work.

Show how you would use the Williamson ether synthesis to prepare the following ethers. You may use any alcohols or phenols as your organic starting materials.

(d) ethyl n-propyl ether (two ways)

(e) benzyl tert-butyl ether (benzyl = Ph–CH₂–)

Show how you would accomplish the following transformations. Some of these examples require more than one step.

(d) 5-chloropent-1-ene → 2-methyltetrahydrofuran 

Show how you would accomplish the following transformations. Some of these examples require more than one step.

(e) 2-chlorohexan-1-ol → 1,2-epoxyhexane

A student wanted to use the Williamson ether synthesis to make (R)-2-ethoxybutane. He remembered that the Williamson synthesis involves an S_N2 displacement, which takes place with inversion of configuration. He ordered a bottle of (S)-butan-2-ol for his chiral starting material. He also remembered that the S_N2 goes best on primary halides and tosylates, so he made ethyl tosylate and sodium (S)-but-2-oxide. After warming these reagents together, he obtained an excellent yield of 2-ethoxybutane.

a. What enantiomer of 2-ethoxybutane did he obtain? Explain how this enantiomer results from the S_N2 reaction of ethyl tosylate with sodium (S)-but-2-oxide.

b. What would have been the best synthesis of (R)-2-ethoxybutane?

c. How can this student convert the rest of his bottle of (S)-butan-2-ol to (R)-2-ethoxybutane?

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)

Show how you would synthesize the following ethers in good yield from the indicated starting materials and any additional reagents needed.

(a) cyclopentyl n-propyl ether from cyclopentanol and propan-1-ol

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.)

(d) 1-methoxy-1-methylcyclopentane

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