Chapter 22: Amines

Summary

• Ammonia reacts as a nucleophile with alkyl halides to give primary amines in a nucleophilic substitution reaction.
• Yields are often poor as the product, a primary amine, RNH₂, is itself a nucleophile and can react with more alkyl halide.
• The result are mixtures containing primary amines, secondary amines, tertiary amines and quaternary ammonium salts.
• This can be avoided if a large excess of ammonia is used.

• As aryl halides do not undergo simple nucleophilic substitution, they cannot be prepared using this method.

• Alkylation of Amines
• Acylation of Amines
• Williamson ether synthesis
• Substitution reactions of Alkyl Halides

MECHANISM OF AMMONIA ALKYLATION
Step 1: The N in ammonia functions as the nucleophile and attacks the electrophilic C of the alkyl halide displacing the bromide and creating the new C-N bond.
Step 2: An acid/base reaction. The base (excess ammonia) deprotonates the positive N (ammonium) center creating the alkylation product, the primary amine.

© Dr. Ian Hunt, Department of Chemistry