8. Elimination Reactions

S_N1 substitution and E1 elimination frequently compete in the same reaction.

b. Compare the function of the solvent (methanol) in the E1 and S_N1 reactions.

Which of the following species is the least nucleophilic?

Rank the following species in each set from best nucleophile to poorest nucleophile.

c. H₂O and NH₃ in methanol

d. Br⁻, Cl⁻, I⁻ in methanol

Which is a better nucleophile?

c. CH₃O⁻ or CH₃OH in H₂O

Which member of each pair is a better nucleophile in methanol?

e. I⁻ or Br⁻

f. Cl⁻ or Br⁻

Rank the following species in each set from best nucleophile to poorest nucleophile.

b.

Rank the following species in each set from best nucleophile to poorest nucleophile.

a.

For each pair, predict the stronger nucleophile in the SN2 reaction (using an alcohol as the solvent). Explain your prediction.

g. (CH₃)₂CHO^– or CH₃CH₂CH₂O^–

h. I^– or Cl^–

Between pyrrole and pyrrolidine, which nitrogen would be most nucleophilic? Why?

In contrast to the results of Assessment 13.18, when a secondary haloalkane is treated with sodium ethanethiolate, we predict formation of a thioether. How is this rationalized?

Which is a better nucleophile?

e. HO⁻ or ^-NH₂ in NH₃

f. HO⁻ or ^-NH₂ in DMSO

For each pair, choose the more reactive nucleophile.

(a)

The zwitterionic form of carbonyls is often used to explain their electrophilicity. Draw the zwitterionic structure of NO⁺₂. Why is this such a great electrophile at the central nitrogen?