Molecular structure, vibrational spectra, HOMO, LUMO and NMR studies of 2,3,4,5,6-Penta Bromo Toluene and Bromo Durene based on density functional calculations

•PBT and BD are used in high impact polystyrene, engineering plastics and cables.•Simulated and observed vibrational spectra are agreed well.•1H and 13C NMR chemical shifts have been compared with experimental values.•The HOMO–LUMO energy gap of PBT and BD are 0.182 and 0.227 a.u.

This work deals with the vibrational spectra of 2,3,4,5,6-Penta Bromo Toluene (PBT) and Bromo Durene (BD) by quantum chemical calculations. The solid phase FTIR and FT-Raman spectra of the title compounds were recorded in the regions 4000–400 cm−1 and 4000–50 cm−1, respectively. The spectra were interpreted with the aid of normal coordinate analysis based on density functional theory (DFT) using B3LYP/6-31G∗ level and basis set combinations and was scaled using various scale factors yielding a good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. The HOMO and LUMO energies were calculated within the molecule. 13C and 1H NMR chemical shifts results were also calculated and compared with the experimental values. Thermodynamical properties like entropy heat capacity, zero point energy have been calculated for the title molecules.

Graphical abstractIn this work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra, HOMO, LUMO, NMR analysis of 2,3,4,5,6-Penta Bromo Toluene and Bromo Durene.Figure optionsDownload full-size imageDownload as PowerPoint slide