BackIn contrast to Assessment 13.102, only one combination of haloalkane and alkoxide can be used in the Williamson ether synthesis to make the ether shown. Identify the combination and explain why it is the only combination that works.
Predict the product of the following reactions. [Two of them are Williamson ether syntheses. Why isn't the other?].
(b)
In Chapter 12, we learned that crown ethers were used to increase the rate of SN2 reactions (Assessment 12.80). Suggest a synthesis of 15-crown-5 using the reactions learned here in Chapter 13.
Suggest a phenoxide and an alkyl halide to make the following aryl alkyl ethers.
(a)
Provide the reagents necessary to carry out the following synthesis. What is the purpose of steps (a) and (e)?
How could you synthesize isopropyl propyl ether, using isopropyl alcohol as the only carbon-containing reagent?
Draw the product of each of the following reactions:
2.
What is the best way to prepare the following ethers using an alkyl halide and an alkoxide ion?
c.
d.
A chemist wanted to synthesize the anesthetic 2-ethoxy-2-methylpropane. He used ethoxide ion and 2-chloro-2-methylpropane for his synthesis and ended up with no ether. What was the product of his synthesis? What reagents should he have used?
Design a synthesis for each of the following, using an intramolecular reaction:
e.
The compound shown below has three different types of OH groups, all with different acidities. Show the structure produced after this compound is treated with different amounts of NaH followed by a methylating reagent. Add a brief explanation.
(a) 1 equivalent of NaH, followed by 1 equivalent of CH3I and heat
(b) 2 equivalents of NaH, followed by 2 equivalents of CH3I and heat
(c) 3 equivalents of NaH, followed by 3 equivalents of CH3I and heat
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 SN2 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 SN2 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 SN2 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?