The experimental and theoretical investigation of the structure of 2, 4 and 6-chloronicotinic acid molecules by vibratioanal spectroscopy

ABSTRACTM.Sc ThesisTHE EXPERIMENTAL AND THEORETICAL INVESTIGATION OF THESTRUCTURE OF 2, 4 AND 6-CHLORONICOTINIC ACID MOLECULES BYVIBRATIOANAL SPECTROSCOPYMehmet ÇINARAfyonkarahisar Kocatepe UniversityGraduate School of Natural and Applied SciencesPHYSICSSupervisor: Assist. Prof. Dr. Mehmet KARABACAKCo-Supervisor: Assoc. Prof. Dr. Mustafa KURTIn this study, infrared and Raman spectra of 2 and 6-chloronicotinic acid were recordedin the region 4000-0 cm-1. The geometric optimizations of the 2, 4 and 6-chloronicotinic acid have been calculated by using the ab initio (HF) and DFTmethods. The molecular geometry and vibrational frequencies of 2, 4 and 6-chloronicotinic acid in the ground state have been calculated by using the Hartree-Fockand density functional methods (B3LYP and B3PW91) with 6-31G (d) and 6-311G (d)as the basis sets. Calculations were carried out using Gaussian 03 package of program.On the basis of the comparison between calculated and experimental geometricparameters of 2 and 6-chloronicotinic acid HF method gives best correlation than theother methods. Comparison of the observed fundamental vibrational frequencies andcalculated results by density functional B3LYP, B3PW91 and Hartree-Fock methodsindicates that B3LYP is superior to the Hartree-Fock and B3PW91 approach formolecular vibrational problems.2007, 129 PagesKeywords: 2-chloronicotinic acid, 4- chloronicotinic acid, 6- chloronicotinic acid,IR, Raman, Hartree-Fock, DFTvi