Anticonvulsant activity of phthalimide was discovered in 2000 by molecular hybridization of thalidomide and ameltolide. In our present research we report some new 4-substituted derivatives of phthalimide with good activity against the tonic and clonic seizures. A series of novel 4-flurophthalimides designed using bioisosteric replacement were synthesized by condensation of 4-flurophthalic anhydride with appropriate arylamines. The purity of these compounds was determined by TLC and the chemical structures were confirmed by IR and 1H-NMR spectroscopy. Anticonvulsant activity of prepared compounds was evaluated using MES and PTZ models. Some of the designed compounds significantly protected mice against the PTZ-induced seizure among which, compound 10 with lipophilic and flexible aromatic moiety was more potent than the reference drug phenytoin and was the most potent in this series of phthalimide derivatives. In the MES model, the prepared phthalimide did not show efficient activity. The prepared compounds are active in clonic seizure.