ABSTRACT. The quinazolinone compounds (1 and 2) in this work were examined for their in vitro antibacterial
activities against gram-positive (Staphylococcus aureus) and gram-negative bacteria (Klebsiella pneumonia,
Proteus bacilli and Shigella flexneri). Compared to the reference antibiotic chloramphenicol, these compounds
showed high antibacterial activities against studied strains with inhibition zones observation. The ground state
geometries have been optimized by using density functional theory (DFT) at B3LYP/6-31G* level of theory. The
absorption spectra have been calculated by using time dependent density functional theory (TDDFT) with and
without solvent. The effect of different functionals (B3LYP, MPW1PW91, and PBE1PBE) on the absorption
wavelengths has been studied. The ionization potential (IP), electron affinity (EA), energy gap (Egap),
electronegativity (χ), hardness (η), electrophilicity (ω), softness (S) and electrophilicity index (ωi) were computed
and discussed. The nonlinear optical (NLO) properties vary by changing the theory (DFT to HF) or functional
(B3LYP to CAM-B3LYP). The physicochemical parameters have been studied by quantitative structure–activity
relationship (QSAR). The computed properties of investigated compounds have been compared with the
Chloramphenicol as well as available experimental data.