Only aliphatic primary amines can be prepared by Gabriel synthesis. Aniline cannot be prepared by this method because aryl halides $\left(\mathrm{C}_6 \mathrm{H}_5 \mathrm{Cl}\right.$ or $\mathrm{C}_6 \mathrm{H}_5 \mathrm{Br}$ ) do not undergo nucleophilic substitution with potassium phthalimide under ordinary conditions to give N -phenyl phthalimide
(i.e., cleavage of $\mathrm{C}-\mathrm{X}$ bond in haloarenes is quite difficult).