Benzene diazonium chloride is prepared by the reaction of aniline with nitrous acid at 273−278K. Nitrous acid is produced in the reaction mixture by reaction of NaNO2 with HCl . C6H5NH2+NaNO2+2‌HCl‌
273−278K
‌───────▶‌
‌C6‌H5‌
+
N
2+‌Cl+NaCl+2H2O Benzene diazonium chloride decomposes easily in the dry state lodobenzene is prepared by shaking benzene diazonium salt with KI because direct insertion of iodine into benzene ring is difficult