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

Explain why bimolecular condensation is a poor method for making unsymmetrical ethers such as ethyl methyl ether.

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) dibutyl ether

(b) ethyl n-propyl ether

(c) di-sec-butyl ether

Propose a mechanism for the following reaction.

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

(a) ethoxycyclohexane + HBr

(b) tetrahydropyran + HI

(c) anisole (methoxybenzene) + HBr

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

(c) anisole (methoxybenzene) + HBr

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

(d)

Boron tribromide (BBr3) 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 BBr₃ (a strong Lewis acid). Propose a mechanism for the reaction of butyl methyl ether with BBr₃ to give (after hydrolysis) butan-1-ol and bromomethane.

Show how you would synthesize butyl isopropyl sulfide using butan-1-ol, propan-2-ol, and any solvents and reagents you need.

Mustard gas, Cl–CH₂CH₂–S–CH₂CH₂–Cl, was used as a poisonous chemical agent in World War I. Mustard gas is much more toxic than a typical primary alkyl chloride. Its toxicity stems from its ability to alkylate amino groups on important metabolic enzymes, rendering the enzymes inactive.

a. Propose a mechanism to explain why mustard gas is an exceptionally potent alkylating agent.

b. Bleach (sodium hypochlorite, NaOCl, a strong oxidizing agent) neutralizes and inactivates mustard gas. Bleach is also effective on organic stains because it oxidizes colored compounds to colorless compounds. Propose products that might be formed by the reaction of mustard gas with bleach.

Show how you would use a protecting group to convert 4-bromobutan-1-ol to hept-5-yn-1-ol.

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

(a) 2-methylpropene → 2,2-dimethyloxirane

(b) 1-phenylethanol → 2-phenyloxirane

(c) 5-chloropent-1-ene → tetrahydropyran

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

The 2001 Nobel Prize in Chemistry was awarded to three organic chemists who have developed methods for catalytic asymmetric syntheses. 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 tartrate ester as the reagents. The following epoxidation of geraniol is typical.

(a) 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?

(b) 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?

(c) Draw the other enantiomer of the product. What reagents would you use if you wanted to epoxidize geraniol to give this other enantiomer?

Propose mechanisms for the epoxidation and ring-opening steps of the epoxidation and hydrolysis of trans-but-2-ene shown above. Predict the product of the same reaction with cis-but-2-ene.

Cellosolve® is the trade name for 2-ethoxyethanol, a common industrial solvent. This compound is produced in chemical plants that use ethylene as their only organic feedstock. Show how you would accomplish this industrial process.

Show the rest of the mechanism for formation of the cyclized intermediate in Figure 14-6.

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

(a) NaOCH₂CH₃ (sodium ethoxide)

(b) NaNH₂ (sodium amide)

(c) NaSPh (sodium thiophenoxide)

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

(d) PhNH₂ (aniline)

(e) KCN (potassium cyanide)

(f) NaN₃ (sodium azide)

Predict the major products of the following reactions, including stereochemistry where appropriate.

a. 2,2-dimethylxirane + H⁺/H₂¹⁸O (oxygen labeled water)

b. 2,2-dimethylxirane + H¹⁸O^–/H₂¹⁸O (oxygen labeled water)

Predict the major products of the following reactions, including stereochemistry where appropriate.

(c) (2S,3R)-2-ethyl-2,3-dimethyloxirane + CH₃O^– / CH₃OH

(d) (2S,3R)-2-ethyl-2,3-dimethyloxirane + H⁺ / CH₃OH

Give the expected products of the following reactions. Include a protonation step where necessary.

(a) 2,2-dimethyloxirane + isopropylmagnesium bromide

(b) propylene oxide + n-butyllithium

(c) cyclopentyloxirane + ethyllithium

Write structural formulas for the following compounds.

(d) divinyl ether

(e) allyl methyl ether

(f) cyclohexene oxide

Write structural formulas for the following compounds.

(g) cis-2,3-epoxyhexane

(h) (2R,3S)-2-methoxypentan-3-ol

(i) trans-2,3-dimethyloxirane

Give common names for the following compounds.

(a) (CH₃)₂CHOCH(CH₃)CH₂CH₃

(b) (CH₃)₃COCH₂CH(CH₃)₂

(c) PhOCH₂CH₃

(d) ClCH₂OCH₂CH₂CH₃

Give common names for the following compounds.

(e)

(f)

Give common names for the following compounds.

(g)

Give IUPAC names for the following compounds.

(g)

(h)

(i)