AbstractThe effect of various common groups on the equilibrium 3 ⇌ 4 is discussed based on the Hammett substituent constants and the values of field and resonance constants calculated by Hansch,et al.N‐Chloroacetyl, dichloroacetyl and trichloroacetyl derivatives of 2‐azidoimidazole were also prepared. The shifting of equilibrium to the tetrazole form does not depend on the whole electron‐attracting effect of a group, but it is mainly governed by its resonance electron‐withdrawin