Density functional theory (DFT), using the B3LYP functional was utilized to study the molecular properties (benzene molecule was a reference) of 1,3,5-Trihydroxybenzene (THB) compound in order to determine the relationship between molecular structure and electrophiles substitutions (nitration) efficiencies to get 2-nitro 1,3,5-Trihydroxybenzene (NTHB), 2,4-Dinitro 1,3,5-Trihydroxybenzene (DNTHB) and 2,4,6-Trinitro 1,3,5-Trihydroxybenzene (TNTHB) respectively. The best geometry for all molecules was investigated at (6-31G) basis sets. The total energies, ionization potentials, electron affinities, energy gaps, hardness and softness were calculated for the studied molecules. The electronic properties for all molecules were investigated by Gaussian (03) program.