Theoretical and Experimental Studies of Vibrational Spectra of 6-fluoronicotinc Acid

Raman and FTIR spectra of 6-fluoronicotinc acid (6FNA) have been analyzed using ab-initio and Density Functional Theory (DFT) calculations. Four stable structures of 6fluoronicotinc acid have been found, the structures differ in orientation of COOH with respect to the nitrogen atom. The optimized geometries, structural parameters, harmonic vibrational wave number and intensity of the vibrational band of the 6-FNA have been calculated using ab-initio MP2/6311++G(d,p) and DFT B3LYP/6-311++G(d,p) level of theories. Vibrational assignments have been made. The optimized geometries and Vibrational frequencies of 6-FNA have been compared with the corresponding values of nicotinic acid (NA). It has been found that 6-FNA is more stable than the corresponding structure of nicotinic acid. Most of the Vibrational frequencies have nearly the same magnitude for 6FNA and NA. However their IR intensities and Raman activities have changed significantly.