Acetone 4,4-Dimethyl-5-oxo-2-pyrazolin-3-ylhydrazone

The title compound, C₈H₁₄N₄O, exhibits an overall molecular coplanarity and trigonal planar geometry of all four N atoms, suggesting resonance interaction extending over eight contiguous atoms. Strong hydrogen bonding between hydrazidic N donor and carbonyl O acceptor atoms results in an almost planar octagonal bridge between two molecules. These dimers are interconnected through a second octagonal bridge of weaker hydrogen bonds between side-chain hydrazine N donor and ring N acceptor atoms, leading to an almost flat linear polymeric structure. The acetone-hydrazone N atom does not participate in hydrogen bonding. From the structure of the title compound, the unequivocal identification of 4,4-dimethyl-5-oxo-2-pyrazolin-3-ylhydrazine, an unexpected byproduct of the reaction of 4,4-dimethylpyrazolidine-3,5-dione with hydrazine, was made.

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