Alkyation of Amines
Alkylation of Amines
Both aromatic and aliphatic amines react with alkyl halides to produce alkylated amines. All three classes of amines i.e., primary, secondary, and tertiary amines react with alkyl halide to produce secondary and tertiary amines and ammonium salts.
The alkylation reaction of amines follows SN2 mechanism. The starting amines attacks on alkyl halide usually primary or secondary alkyl halides. This reaction is not feasible with tertiary alkyl halides due to steric hindrance.
The ammonium cation gets deprotonated by another amine molecule and restores the nucleophilic character of the first product. This reaction repeats until all amines are converted to quaternary ammonium salts.
Meanwhile, the use of secondary alkyl halides can also produce elimination products. The use of excess alkyl halide to produce entirely ammonium salts of amines is called exhaustive alkylation. If the excess alkyl halide is methyl halide, then the reaction is called exhaustive methylation.
Hence, we can conclude that the alkylation of amines via SN2 mechanism is not a good way to synthesize desired amine derivatives. To overcome the problem of production of mixture of different amines, the alkyl halides are used in excess. This ensures the production of ammonium salts.
Furthermore, mild bases like sodium bicarbonate (NaHCO3) and dilute sodium hydroxide (NaOH) are used to deprotonate the intermediates formed during the reaction and neutralize the HX acids formed.
