Normal Modes, Molecular Orbitals and Thermochemical Analyses of 2,4 and 3,4 Dichloro Substituted Phenyl-N-(1,3-thiazol-2-yl)acetamides: DFT Study and FTIR Spectra

Abstract

A detailed spectroscopic analysis of two dichloro substituted phenyl-N-(1,3-thiazol-2-yl)acetamides at 2,4 and 3,4 positions of the phenyl ring has been carried out by using B3LYP method with 6-31+G(d, p) basis set within density functional scheme. The scaled theoretical wave numbers are in perfect agreement with the experimental values and the vibrational modes are interpreted in terms of potential energy distribution (PED). The internal coordinates are optimized repeatedly to maximize the PED contributions. The molecular HOMO-LUMO surfaces, their respective energy gaps, and MESP surfaces have also been drawn to explain the chemical activity of both molecules. Various thermodynamic parameters are presented at the same level of theory.

Uniform versus Nonuniform Scaling of Normal Modes Predicted by Ab Initio Calculations: A Test on 2-(2,6-Dichlorophenyl)-N-(1,3-thiazol-2yl) Acetamide

“…Hence, it may be expected that the normal modes analysis from theoretically predicted force field reflects well the modes of vibrations in a real molecule. Normal-mode analysis is commonly employed in the interpretation of the vibrational spectra of molecules [1][2][3][4]. However, there are some limitations of the model used to calculate the vibrational frequencies.…”