Benzenesulfonamide compounds containing piperazine heterocycles have prospective pharmacological activity. Two benzenesulfonamide compounds were synthesized. Based on density functional theory (DFT), the optimized structures of the two molecules were calculated using the B3LYP method. DFT was also used for further study of the molecular electrostatic potential and leading molecular orbital. Single crystal of 1-ethyl-4-(phenylsulfonyl)piperazine was studied. The intermolecular interaction and contact were quantified using Hirshfeld surface analysis and 2D fingerprint plots. Conformational analysis showed that the molecular structure after DFT optimization was consistent with the crystal structure determined by x-ray single crystal diffraction.