Classify the following amines as primary,secondary,or tertiary:
$(i)$ $1-$naphthylamine
$(ii)$ $N,N$-dimethyl$-1-$naphthylamine
$(iii)$ $(C_2H_5)_2CHNH_2$
$(iv)$ $(C_2H_5)_2NH$

(N/A) The classification of amines is based on the number of alkyl or aryl groups attached to the nitrogen atom.
$(i)$ $1-$naphthylamine: The nitrogen atom is attached to one aryl group and two hydrogen atoms. Therefore,it is a primary $(1^{\circ})$ amine.
$(ii)$ $N,N$-dimethyl$-1-$naphthylamine: The nitrogen atom is attached to one aryl group and two methyl groups. Therefore,it is a tertiary $(3^{\circ})$ amine.
$(iii)$ $(C_2H_5)_2CHNH_2$: The nitrogen atom is attached to one alkyl group and two hydrogen atoms. Therefore,it is a primary $(1^{\circ})$ amine.
$(iv)$ $(C_2H_5)_2NH$: The nitrogen atom is attached to two alkyl groups and one hydrogen atom. Therefore,it is a secondary $(2^{\circ})$ amine.
Summary:
Primary $(1^{\circ})$: $(i)$ and $(iii)$
Secondary $(2^{\circ})$: $(iv)$
Tertiary $(3^{\circ})$: $(ii)$