FT-IR and FT-Raman Spectra, HOMO-LUMO and NBO Analysis of 2-Bromo-4-Nitrotoluene: an Ab Initio and DFT Approach

M. Karnan; M. Murugan; V. Balachandran; M. K. Murali
The FT-IR and FT-Raman spectra of 2-bromo-4-nitrotoluene (BNT) have been recorded in the region 4000-400 cm-1 and 3500-100 cm-1, respectively. The optimized molecular geometry, vibrational frequencies, Infrared intensities, Raman intensities and thermodynamic parameters in ground state were calculated using ab initio Hartree-Fock (HF) and density functional B3LYP methods (DFT) with 6-311++G(d,p) basis set. The observed FT-IR and FT-Raman vibrational frequencies are analysed and compared with theoretically predicted vibrational frequencies. The geometries and normal modes of vibration obtained from HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) methods are reliable compared with the experimental data. The Mulliken charges, the natural bonding orbital (NBO) analysis and thermodynamic functions of the investigated molecule were computed using HF and DFT calculations. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The influences of bromine and nitrogen atoms and methyl group on the geometry of benzene and its normal modes of vibrations have also been discussed.
Vibrational Spectra; HF; DFT; HOMO-LUMO; NBO; 2-Bromo-4-Nitrotoluene
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