FT-IR, FT-Raman spectra and ab initio HF and DFT calculations of 2-nitro- and 4-nitrobenzaldehydes

1632-1641Combined experimental and theoretical studies on molecular and vibrational structure of 2-nitrobenzaldehyde and 4-nitrobenzaldehydes are reported. The Fourier transform infrared and Fourier transform Raman spectra of 2NB and 4NB has been recorded in the solid phase. The optimized geometry has been calculated by HF and B3LYP methods with 6-311++G(d,p) basis set. The harmonic vibrational frequencies of the title compounds have been performed at the same level of theories. The scaled theoretical wave numbers show very good agreement with the experimental values. The thermodynamic functions of the title compounds have also been computed at HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels of theory. A detailed interpretation of the infrared and Raman spectra of 2NB and 4NB is reported. The theoretical FT-IR spectra of the title molecules have also been constructed

Molecular structure and vibrational spectra of 2-chlorobenzoic acid by density functional theory and <i>ab-initio</i> Hartree-Fock calculations

248-258The structure, harmonic frequencies and vibrational mode assignments for 2-chlorobenzoic acid (2CBA) monomer are calculated using HF and DFT methods employing the 6-311++G(d,p) basis set. The results of the molecular structure and vibrational frequencies obtained on the basis of calculations are presented and critically compared with the experimental IR data recorded in gas phase. The Raman and IR spectral data of 2-chlorobenzoic acid (2CBA) obtained in solid phase have also been included. The normal mode analysis has been carried out for all the modes. Most of the modes have wavenumbers in the expected range. The experimental spectra also coincide satisfactorily with those of theoretically constructed spectrograms