Molecular structures of two 3-pyrazolidone compounds with potent anticonvulsant activity

The crystal and molecular structures of two potent anticonvulsant compounds:1 - (n - butyl) - 5 - (p - fluorophenyl) - 3 - pyrazolidone(1) and 1 - (n - propyl) - 5 - (p - methylphenyl) - 3 - pyrazolidone(2) were determined by X - ray diffraction method. The atomic net charges were calculated by CNDO/2 method. It is shown that the bond lengths of C-N and C-O of the conjugated amido groups and the atomic net charges in the five membered rings of 3 - pyrazolidones are affected by the electronreleasing capabilities of R(1) groups. It is considered that a substituent being more electron - releasing at position 1 of the five membered ring of 3 pyrazolidone is favorable on enhancement of the anticonvulsant activity, and the substituent at position 5 might mainly affect the molecular steric shape and the hydrophobic property.