Article ID Journal Published Year Pages File Type
1229565 Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2014 11 Pages PDF
Abstract

•Experimental FT-IR and FT-Raman spectra recorded for CTFP and BTFP.•Theoretical spectra were interpreted with the aid of normal coordinate analysis.•The wavenumbers are assigned using PED analysis.•HOMO, LUMO, local reactivity and chemical reactivity were performed.•Thermodynamic properties and their correlations with temperature have been obtained.

Quantum mechanical calculations of energies, geometries and vibrational wave numbers of 3-chloro-2,4,5,6-tetrafluoropyridine and 4-bromo-2,3,5,6-tetrafluoropyridine have been performed by DFT level of theory using B3LYP/6-31+G(d) and B3LYP/6-311++G(d,p) as basis sets. The optimized geometrical parameters obtained by B3LYP method show good agreement with experimental data. The difference between the observed and scaled wave number values of most of the fundamentals is very small. A detailed interpretation of the FT-IR and FT-Raman spectra of 3-chloro-2,4,5,6-tetrafluoropyridine and 4-bromo-2,3,5,6-tetrafluoropyridine were also reported. Molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO). The calculated HOMO and LUMO energies show that charge transfer occurs in the molecules. Information about the size, shape, charge density distribution, and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential (ESP). Thermodynamic properties (heat capacity, entropy and enthalpy and Gibb’s free energy) of the title compounds at different temperatures were calculated.

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Physical Sciences and Engineering Chemistry Analytical Chemistry
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