91Ó°ÊÓ

Predict the major product when each reagent reacts with ethylene oxide.

(a) NaOCH₂CH₃(Sodium ethoxide)

(b) NaNH₂(sodium amide)

(c) NaSPh (sodium thiophenoxide)

(d) PhNH₂(aniline)

(e) KCN (potassium cyanide)

(f) NaN₃(soidum azide)

Question. Show how you would make the following ethers, using only simple alcohols and any needed reagents as your starting materials.

(a)1-methoxypropane

(b) 2-ethoxy-2-methylbutane

(c) 4-methylbenzyl cyclopentyl ether

(d) Trans-2-ethoxycyclohexanol

(e) The TIPS ether of (d)

(f) 4-methylcyclohexyl cyclopentyl 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.)

1. 2-methoxybutane
2. Ethyl cyclohexyl ether
3. 1-methoxy-2-methylcyclopentane
4. 1-methoxy-1-methylcyclopentane
5. 1-isopropoxy-1-methylcyclopentane
6. Tert-butyl phenyl ether

Question. Propose a mechanism for the acid-catalyzed condensation of n-propyl alcohol to n-propyl ether, as shown above. When the temperature is allowed to rise too high, propene is formed. Propose a mechanism for the formation of propene and explain why it is favored at higher temperatures.

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) $\mathbf{\text{»å¾±²ú³Ü³Ù²â±ô â¶Ä‰e³Ù³ó±ð°ù}}$

(b) $\mathbf{\text{±ð³Ù³ó²â±ô â¶Ä‰n-±è°ù´Ç±è²â±ô â¶Ä‰e³Ù³ó±ð°ù}}$

(c) $\mathbf{\text{»å¾±-²õ±ð³¦-²ú³Ü³Ù²â±ô â¶Ä‰e³Ù³ó±ð°ù}}$

Question. Propose a mechanism for the following reaction.

Predict the products of the following reactants. An excess acid is available in each case.

(c) anisole ( methoxybenzene) + HBr

(d)

(e)

Boron tribromide$\left({\mathrm{BBr}}_3\right)$cleaves ethers to give alkyl halides and alcohols.

The reaction is thought to involve attack by a bromide ion on the Lewis acid-base adduct of the ether with$\mathbf{\left(}{\mathbf{BBr}}_{\mathbf{3}}\mathbf{\right)}$(a strong Lewis acid). Propose a mechanism for the reaction of butyl methyl ether with$\mathbf{\left(}{\mathbf{BBr}}_{\mathbf{3}}\mathbf{\right)}$to give (after hydrolysis) butan-1-ol and bromomethane.

Rank the given solvents in decreasing order of their ability to dissolve each compound

(a) HCOO^-Na⁺

(b)

(c)

Solvents

Ethyl ether, water, ethanol, dichloromethane

Question. The 2001 Nobel Prize in Chemistry was awarded to three organic chemists who have developed methods for catalytic asymmetric synthesis. An asymmetric (or enantioselective) synthesis is one that converts an achiral starting material into mostly one enantiomer of a chiral product. K. Barry Sharpless (The Scripps Research Institute) developed an asymmetric epoxidation of allylic alcohols that gives excellent chemical yields and greater than 90% enantiomeric excess.

The Sharpless epoxidation uses tert-butyl hydroperoxide, titanium(IV) isopropoxide, and a dialkyl tartarate ester as the reagents. The following epoxidation of geraniol is typical.

1. Which of these reagents is most likely to be the actual oxidizing agent? That is, which reagent is reduced in the reaction? What is the likely function of the other reagents?
2. When achiral reagents react to give a chiral product, that product is normally formed as a racemic mixture of enantiomers. How can the Sharpless epoxidation give just one nearly pure enantiomer of the product?
3. Draw the other enantiomer of the product. What reagents would you use if you wanted to epoxidize geraniol to give this other enantiomer?