12. Alcohols, Ethers, Epoxides and Thiols

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

Give two sets of reactants (each set including an alkyl halide and a nucleophile) that could be used to synthesize the following ether:

What is the best way to prepare the following ethers using an alkyl halide and an alkoxide ion?

a.

b.

Which of following ethers cannot be made by a Williamson ether synthesis?

a. Propose a mechanism for the following reaction:

(a) Show how ethanol and cyclohexanol may be used to synthesize cyclohexyl ethyl ether (tosylation followed by the Williamson ether synthesis).

(b) Why can't we synthesize this product simply by mixing the two alcohols, adding some sulfuric acid, and heating?

A good Williamson synthesis of ethyl methyl ether would be

What is wrong with the following proposed synthesis of ethyl methyl ether? First, ethanol is treated with acid to protonate the hydroxy group (making it a good leaving group), and then sodium methoxide is added to displace water.

Phenols (pK_a ≈ 10) are more acidic than other alcohols, so they are easily deprotonated by sodium hydroxide or potassium hydroxide. The anions of phenols (phenoxide ions) can be used in the Williamson ether synthesis, especially with very reactive alkylating reagents such as dimethyl sulfate. Using phenol, dimethyl sulfate, and other necessary reagents, show how you would synthesize methyl phenyl ether.

Identify the two possible combinations of haloalkane and alkoxide that can be used to make the following ether.

The reaction of alkoxides with haloalkanes is not a viable way to form ethers. (a) Why? (b) Why can thioethers be formed by an analogous reaction?

How could the reaction in Figure 13.67(b) be modified to produce the following ether?

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.)

a. 2-methoxybutane

b. ethyl cyclohexyl ether

c. 1-methoxy-2-methylcyclopentane