The conformation and vibration analysis of 2-, 3- and 4-pyridinecarbonyl chlorides have been computed using B3LYP hybrid density functional with 6-311++G** basis set. All structures have been fully optimized, and the optimized geometries, dipole moments, infrared vibrational frequencies and relative energies are reported. From the computations, 2-pyridinecarbonyl chloride is predicted to exist predominantly in trans conformation, while the 3-pyridinecarbonyl chloride is predicted to exist predominantly in cis conformation with the trans-cis rotational barrier of 4.63 and 5.48 kcal/mol respectively. The two equivalent planar structures of 4-pyridinecarbonyl chloride are separated by an energy barrier of 4.55 kcal/mol. The effect of solvents on the conformational stability have been examined for nine different solvents (heptane, chloroform, THF, dichloroethane, acetone, ethanol, methanol, DSMO and water). The Integral Equation Formalism version of Polarized Continuum model (IEF-PCM) used for all solution phase computations. The trans conformer of 2-pyridinecarbonyl chloride and the cis conformer of 3-pyridinecarbonyl chloride which are more stable in gas phase remain the stable confomers in solution, but the stability decreases as the dielectric constant of the solvent increases. The variation of relative energies, dipole moments, solvation energies as function of the dielectric constant of solvents has been investigated.
On the occasion of his 60th birthday, Sahar Abdalla acknowledges a most relaxing working atmosphere with Prof. Dr. Michael Springborg during her PhD course at University of Saarland.
©2016 Walter de Gruyter Berlin/Boston