Ammonolysis of alkyl halides followed by the treatment with NaOH  can be used to prepare primary,secondary and tertiary amines.

The purpose of NaOH in the reaction is:

Free amine obtained from ammonium salt with NaOH, & acidic impurities are removed by NaOH

$\begin{array}{l}R-X+N{H}_3\to RN{H}_3^{+}{X}^{-}\\ RN{H}_3{X}^{-}+NaOH\to R-N{H}_2+NaX+H_{2}O\end{array}$

Similarly 2°, 3° amines can also be prepared