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.

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

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

A graduate student attempted the following reaction and did not isolate the expected product.

(a) What product did they isolate?

(b) What reagent should they have used instead to get their desired product?

Suggest the appropriate reagents to carry out the following transformations.

(f)

Suggest a reagent for the transformation of a 1° alcohol to a 1° alkyl halide.

Suggest the appropriate reagents to carry out the following transformations.

(e)

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

c.

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.

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

(d) concentrated HBr

(e) TsCl/pyridine, then NaBr

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)

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

(a) PBr₃

(b) SOCl₂ 

(c) Lucas reagent

Suggest how you would convert trans-4-methylcyclohexanol to

a. trans-1-chloro-4-methylcyclohexane.

b. cis-1-chloro-4-methylcyclohexane.

What stereoisomers do the following reactions form?

a.

b.

What stereoisomers do the following reactions form?

c.

d.