Molecular structure and vibrational spectra of o-chlorotoluene, m-chlorotoluene, and p-chlorotoluene by ab initio HF and DFT calculations

In this work, experimental and theoretical study on the molecular structure and the vibrational spectra of o-chlorotoluene (OCT), m-chlorotoluene (MCT) and p-chlorotoluene (PCT) are presented. The vibrational frequencies of these compounds were obtained theoretically by ab initio HF and DFT/B3LYP calculations employing the standard 6-311++G(d,p) basis set for optimized geometries and were compared with Fourier transform infrared (FTIR) in the region of 400–4000 cm−1 and with Raman spectra in the region of 100–4000 cm−1. Complete vibrational assignment, analysis and correlation of the fundamental modes for these compounds have been carried out. The vibrational harmonic frequencies were scaled using scale factors, yielding a good agreement between the experimentally recorded and the theoretically calculated values.