12. Alcohols, Ethers, Epoxides and Thiols

Show how you would convert (S)-hexan-2-ol to

(a) (S)-2-chlorohexane.

(b) (R)-2-bromohexane.

(c) (R)-hexan-2-ol.

Both cis- and trans-2-methylcyclohexanol undergo dehydration in warm sulfuric acid to give 1-methylcyclohexene as the major alkene product. These alcohols can also be converted to alkenes by tosylation using TsCl and pyridine, followed by elimination using KOC(CH₃)₃ as a strong base. Under these basic conditions, the tosylate of cis-2-methylcyclohexanol eliminates to give mostly 1-methylcyclohexene, but the tosylate of trans-2-methylcyclohexanol eliminates to give only 3-methylcyclohexene. Explain how this stereochemical difference in reactants controls a regiochemical difference in the products of the basic elimination, but not in the acid-catalyzed elimination.

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

(a) 1-methoxybutane

(b) 2-ethoxy-2-methylpropane

(c) benzyl cyclopentyl ether

Suggest the appropriate reagents to carry out the following transformations.

(f)

In each case, show how you would synthesize the chloride, bromide, and iodide from the corresponding alcohol.

(a) 1-halobutane (halo = chloro, bromo, iodo)

(b) halocyclopentane

Predict the major products (including stereochemistry) when cis-3-methylcyclohexanol reacts with the following reagents.

(a) PBr₃

(b) SOCl₂ 

(c) Lucas reagent

Give the structures of the products you would expect when each alcohol reacts with (1) HCl, ZnCl₂; (2) HBr; (3) PBr₃; (4) P/I₂; and (5) SOCl₂.

(a) butan-1-ol

(b) 2-methylbutan-2-ol

Starting with (R)-1-deuterio-1-propanol, how could you prepare

b. (S)-1-deuterio-1-methoxypropane?

Show how you would synthesize the following compounds. As starting materials, you may use any alcohols containing four or fewer carbon atoms, cyclohexanol, and any necessary solvents and inorganic reagents.

(g)

Suggest the appropriate reagents to carry out the following transformations.

(e)

When SOCl₂ is used in place of HCl, only one product results. Why are these conditions better?

Using cyclohexanone as the starting material, describe how each of the following compounds can be synthesized:

c.

Predict the major products (including stereochemistry) when cis-3-methylcyclohexanol reacts with the following reagents.

(d) concentrated HBr

(e) TsCl/pyridine, then NaBr

What stereoisomers do the following reactions form?

a.

b.