Hydrolysis of an halide is nucleophilic substitution reaction, which is possible in aryl halides only when some powerful electron withdrawing groups (like −−NO2,−−COOH etc.) are attached to especially o- and p-positions. Thus 2, 4, 6-trinitrochloro benzene will undergo hydrolysis (aq. KOH) most readily as it has 3−e− -withdrawing groups.