in the dark for 4 days. During this period the evolution of gases ceased and a clear solution was obtained. The reaction mixture was diluted with water (50 ml) and neutralized with solid sodium bicarbonate. In addition, 30 ml of water was added and the whole extracted with six portions of 50 ml of chloroform. The combined extracts were dried over anhydrous sodium sulfate and then evaporated to dryness to obtain 0.83 g of a residue.By thin layer chromatography on silica gel, using commercially available plates (DC-Fertigplatten Kieselgel F 254, Merck) and developing them with ethyl acetate, it could be shown that the obtained product was a mixture of the starting compound (Rt 0.59) 'and 3-azidopyridazine 1-oxide (Rt 0.45) (detection in uv light).A solution of 300 mg of the crude product in 3 ml of chloroform was separated on a chromatoplate with the above-mentioned absorbent, and the part containing the azide was separated and the compound eluted with chloroform. Upon evaporation of the solvent 12 mg of the residue which consisted of practically pure 3-azidopyridazine 1-oxide10 was obtaind (yield 2.4%); mp 151-152°and mixture melting point with an authentic specimen obtained from nitrosation of 3-hydrazinopyridazine 1-Kinetics of Deuteration of Imidazole 1141 oxide12 was undepressed. Moreover, ir spectra of both products were identical [2179 and 2146 cm-1 (Na) and 1263 cm-1 (N-O)].

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