1H-Tetrazol-5(4H)-one

The molecular structure determination of the title compound, CH₂N₄O, by X-ray crystallography reveals that it is 1H-tetrazol-5(4H)-one, not 5-hydroxytetrazole which had been generally accepted; 1H-tetrazol-5(4H)-one is the keto form with C_2v symmetry. Ab initio calculations at the MP2/6-31 G* level also indicate that 1H-tetrazol-5(4H)-one is the most stable tautomer.

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