Etude de l'encombrement stérique des méthyles dans les produits aromatiques

Abstract

This work is a part of study of the crystal structure and experimental(X-rays diffraction method) and calculated molecular conformation (DFT density functional theory) of an organic and aromatic material. The choice of dibromonitrotoluene (C7H5Br2NO2), is mainly dictated by the possible application of the obtained results in medical and pharmacologic domain, add to that, the planety of the molecule which allows in fact DFT precise calculates. The crystalline structure of dibromonitrotoluene was determinated at 293k witch is triclinic (p-1, z =2). Thermal agitation is very significant for methyl group compared to the other atoms of the molecule. The conformation of the dibromonitrotoluene molecule (C7H5Br2NO2), was calculated by DFT method with the functional B3LYP, MPW1PW91 using the bases Lanl2DZ, 6-311 . The infra-red spectroscopy at the ambient temperature allowed the observation of internal vibrational modes towards: 665, 739, 791, 995, 1120, 1340, 1520; 3090 cm-1 .Calculation of IR spectroscopy held in quantum Chemistry allowed the attribution of frequencies to the different vibrational modes of the molecule