The optimized molecular geometry, vibrational frequencies, atomic charges, dipole moment, rotational constants and several thermodynamic parameters of 5-chloro-3-(2-(4-ethylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one (abbreviated as CEOT) molecule in the ground state were calculated using ab initio Hartree-Fock (HF) and Density Functional B3LYP methods (DFT) with 6-311++G(d,p), 6-311G(d,p), 6-31++G(d,p) and 6-31G(d,p) basis sets. The Fourier-transform infrared (FT-IR) spectrum of CEOT has been recorded in the region 4000-400 cm(-1). The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR spectrum. Energy gap of the molecule was found using HOMO and LUMO calculation, hence the less band gap, which seems to be more stable. The observed and calculated vibrational frequencies are found to be in good agreement. (c) 2014 Published by Elsevier B.V.