Spectroscopic (FT-IR, FT-Raman), first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis of N-[(4-(trifluoromethyl)phenyl]pyrazine-2-carboxamide by density functional methods

The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of N-[(4-(trifluoromethyl)phenyl]pyrazine-2-carboxamide have been investigated experimentally and theoretically using Gaussian09 software package. Potential energy distribution of normal modes of vibrations was done using GAR2PED program. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. From the NBO analysis it is evident that the increased electron density at the nitrogen and carbon atoms leads to the elongation of their respective bond lengths and a lowering of their corresponding stretching wavenumbers. The calculated geometrical parameters are in agreement with that of similar derivatives. The calculated first hyperpolarizability is high and the calculated data suggest an extended π-electron delocalization over the pyrazine ring and carboxamide moiety which is responsible for the nonlinearity of the molecule.