A primary amine, `RNH_(2)` can be reacted with `CH_(3)-X` to get secondary amine, `R-NHCH(3)`, but the only disadvantage is that `3^(@)` amine and quaternary ammonium salts are also obtained as side products. Can your suggest a method where `RNH_(2)` forms only `2^(@)` amine?

Explanation

`1^(@)` Amines react with `CHCl_(3)` in presence of alcoholic KOH to form isocyanides which upon catalytic reduction give `2^(@)` amines.
`underset(1^(@)" Amine")(RNH_(2)) underset(("Carbylamine reaction"))overset(KOH//CHCl_(3))to R-overset(to)(=)C underset(("Catalytic reduction"))overset(H_(2)//Pt)to underset(2^(@)" amine")(R-NH-CH_(3))`