We Know that: Amines are generally basic in naturebecause of their ability to donate the lone pair of electrons onthe Nitrogen atom. the presence of electronwithdrawinggroup decreases the basicity of the amines. For the given aminesp-Nitro aniline is least basic as the pKaindicates that p-Nitroaniline is Acidic in nature. Solution We Know that: Amines are generally basic in naturebecause of their ability to donate the lone pair of electrons onthe Nitrogen atom. the presence of electronwithdrawinggroup decreases the basicity of the amines. For the given aminesp-Nitro aniline is least basic as the pKaindicates that p-Nitroaniline is Acidic in nature..