8. Elimination Reactions

For each pair, choose the more reactive nucleophile.

(a)

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?

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

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?

Would you expect the following bases to favor E1 or E2 elimination?

(c)

For each pair, choose the more reactive nucleophile.

(b)

Would you expect methoxide ion to be a better nucleophile if it is dissolved in CH₃OH or if it is dissolved in DMSO? Why?

Indicate which species in each pair gives a higher substitution-product-to-elimination-product ratio when it reacts with isopropyl bromide:

a. ethoxide ion or tert-butoxide ion

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

a. (CH₃CH₂)₃N or (CH₃CH₂)₂NH

b. (CH₃)₂O or (CH₃)₂S

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^–

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 nucleophile would be more reactive in the solvent given

(c)