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

Abstract

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. (13)C and (1)H 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.

Keywords: (13)C NMR and (1)H NMR; 2,3,4,5,6-Penta Bromo Toluene; Bromo Durene; HOMO; LUMO; Vibrational spectra.