Chemistry Reference
In-Depth Information
9. Arrange the following structures in order of increasing nucleophilicity:
When a nucleophilic atom is surrounded by additional substituents, the degree of
nucleophilicity is altered. This observation is explained because nucleophilicity
depends, in part, on the ability of a given nucleophile to react with electrophiles. If
the nucleophilic atom cannot approach the electrophile because of steric congestion
surrounding the nucleophilic atom, then the nucleophile is rendered less effective as
a nucleophile and more effective as a base.
Based on the above argument, the order of increasing nucleophilicity for this group of
amines is shown below. Regarding the first two amines, the piperidine is more
nucleophilic because, unlike tert-butyl isobutylamine, the alkyl groups are tied
back into a ring and not able to move. This allows the nitrogen to more readily
present its lone pair.
Based on the above argument, the order of increasing nucleophilicity for this group of
alkyl anions is shown below.
10. For the following pairs of structures, circle the better leaving group.
