Vibrational spectroscopic, electronic and quantum chemical investigations on 2,3-hexadiene

Abstract

The Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectra of 2,3-hexadiene have been recorded in the regions 3400–400 and 3400–100 cm −1, respectively. A complete assignment and analysis of the fundamental vibrational modes of the molecule were carried out. The observed fundamental modes have been compared with the harmonic vibrational frequencies computed using HF and DFT (B3LYP, B3PW91) methods by employing 6-31G(d,p) and 6-311++G(d,p) basis sets. The scaled vibrational frequencies are found to coincide with the experimentally observed values. Theoretical infrared and Raman spectra at HF and DFT levels have been constructed and compared with the experimental spectra. A comparative study of computed optimised geometrical parameters, infrared and Raman intensities, thermodynamic values and frequencies obtained by different quantum mechanical methods were presented. Molecular electrostatic potential, total density distribution and frontier orbital energy levels are constructed to understand the electronic properties. The most stable geometry of the compound under investigation has been determined from the potential energy surface scan.