7. Substitution Reactions

For each pair of compounds, state which compound is the better S_N2 substrate.

c. 2-bromobutane or isopropyl bromide

d. 1-chloro-2,2-dimethylbutane or 2-chlorobutane

e. 1-iodobutane or 2-iodopropane

For each pair, choose the nucleophile that would react most quickly in an S_N2 reaction (assume H₂O is the solvent).

(b)

Will the following S_N2 reaction proceed more rapidly in DMSO or H₂O?

Draw a perspective structure or a Fischer projection for the products of the following S_N2 reactions.

(a) trans-1-bromo-3-methylcyclopentane + KOH

(b) (R)-2-bromopentane + KCN

Show how you might use SN2 reactions to convert 1-chlorobutane into the following compounds.

e. CH₃—(CH₂)₃—C≡CH

f. CH₃CH₂—O—(CH₂)₃—CH₃

g. CH₃—(CH₂)₃—NH₂

What stereoisomers do the following reactions form?

d.

Draw a perspective structure or a Fischer projection for the products of the following S_N2 reactions.

(e)

Predict the major products of the following substitutions.

e. 1-chloropentane + NaI →

Which of the following represents the correct organic and inorganic products for the SN2 reaction of $\mathrm{CH}{3}_0\mathrm{Br}$ with $\mathrm{OH}-$ in aqueous solution?

Which S_N2 reaction would you expect to be faster? Explain your answer.

Show how each compound might be synthesized by the SN2 displacement of an alkyl halide.

e. H₂C=CH—CH₂CN

f. H—C≡C—CH₂CH₂CH₃

2-Acetoxycyclohexyl tosylate reacts with acetate ion to form 1,2-cyclohexanediol diacetate. The reaction is stereospecific—that is, the stereoisomers obtained as products depend on the stereoisomer used as a reactant. Recall that because 2-acetoxycyclohexyl tosylate has two asymmetric centers, it has four stereoisomers—two are cis and two are trans. Explain the following observations:

c. A trans reactant is more reactive than a cis reactant.

Which alkyl halide is more reactive in an S_N2 reaction with a given nucleophile?

a.

b.

Predict the major products of the following reactions.

(a) ethyl tosylate + potassium tert-butoxide

(b) isobutyl tosylate + NaI

(c) (R)-2-hexyl tosylate + NaCN