Exhaustive alkylation.

Explanation

The process of converting a `1^(@),2^(@)` or `3^(@)` amine into its quaternary ammonium salt on treatment with excess of an alkyl halide is called exhaustive alkylation. The process is called exhaustive methylation if the alkyl halide used is methyl iodine.
`underset((1^(@)))underset("Methyl iodine")(CH_(3)NH_(2))underset(-HI)overset(CH_(3)I)(to)underset((2^(@)))underset("Dimethylamine")((CH_(3))_(2)NH)underset(-HI)overset(CH_(3)I)(to)underset((3^(@)))underset("Trimethylamine")((CH_(3))_(3)N)overset(CH_(3)I)(to)underset("(Quaternary salt)")underset("Tetramethylammonium iodide")((CH_(3))_(4)N^(+)I^(-))`