Hydrazones of 5 (6)-Benzimidazolylhydrazine (I-XIII). A solution of 2.22 g (0.01 mole) of 5 (6)- hydrazinobenzimidazole dihydrochloride in 5-10 ml of water is treated with an equimolar amount of the appropriate carbonyl compound, and heated on a water bath for 10-30 min,