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RESEARCH PRODUCT

π-Electron delocalization in 2-benzoyl-5-phenylpyrazolidin-3-one

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Abstract The crystal and molecular structures of 2-benzoyl-5-phenylpyrazolidin-3-one have been characterized by X-ray diffraction along with density functional theory studies. Cinnamic acid chloride was reacted with benzhydrazide, yielding 2-benzoyl-5-phenylpyrazolidin-3-one. This product was formed in the transformation comprising the nucleophilic addition of benzhydrazide to the styryl fragment of the α,β-unsaturated arrangement and subsequent cyclization. The molecule contains two benzene rings and one five-membered heterocyclic ring with an N–N single bond. The five-membered ring is composed of three atoms of sp 3 hybridization and two atoms of sp 2 hybridization, which cause the flattening of the heterocyclic ring. The Harmonic Oscillator Model of Aromaticity and Nucleus-Independent Chemical Shift indexes, calculated for the benzene rings, demonstrate that there are no substantial interactions between the regions of π-electron delocalization in the molecule. In the crystal structure, there are N–H···O hydrogen bonds that link the molecules along the crystallographic c axis and weak intermolecular C–H···O hydrogen bonds.