Vibrational, conformational and electronic structure investigations of α,α′-dibromo-o-xylene, α,α′-dibromo-m-xylene and α,α′-dibromo-p-xylene

The Fourier transform infrared (FTIR) and FT-Raman spectra of α,α′-dibromo-o-xylene (DBOX), α,α′-dibromo-m-xylene (DBMX) and α,α′-dibromo-p-xylene (DBPX) of the configuration BrCH2C6H4CH2Br have been recorded in the range 4000–400 and 4000–100 cm−1, respectively. The conformational analysis of these compounds was performed. The complete vibrational assignment and analysis of the fundamental modes of the most stable conformer of the compounds were carried out using the experimental FTIR and FT-Raman data, and quantum mechanical studies. The observed vibrational frequencies were compared with the wavenumbers derived theoretically for the optimized geometry of the compounds from the DFT-B3LYP gradient calculations employing the standard 6-31G**, high level 6-311++G** and cc-pVTZ basis sets. The structural parameters and vibrational wavenumbers obtained from the DFT method are in good agreement with the experimental data. The potential energy distributions of the fundamental modes were also calculated with DFT force fields utilizing Wilson's FG matrix method. The effect of CH2Br group on the skeletal vibrations has been discussed.

Graphical abstractThe conformational analysis of α,α′-dibromo-o-xylene (DBOX), α,α′-dibromo-m-xylene (DBMX) and α,α′-dibromo-p-xylene (DBPX) of the configuration BrCH2C6H4CH2Br were performed. The complete vibrational assignment and analysis of the fundamental modes of the most stable conformer of the compounds were carried out using the experimental FTIR and FT-Raman data, and quantum mechanical studies.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► FTIR and FT-Raman investigations of α,α′-dibromo-o-xylene, α,α′-dibromo-m-xylene and α,α′-dibromo-p-xylene were carried out. ► Energy, structural, thermodynamical and vibrational characteristics were determined. ► The conformational analysis of these compounds was performed. ► The electronic properties and NBO analysis were carried out. ► Steric effect of bromomethyl group on the benzene ring parameters has been analyzed.