Natural Bond Orbital Analysis of 2-Chloro-7-Methylquinoline-3-Carbaldehyde

Abstract

Quinolines are aromatic compounds formed from benzene rings and fused to these rings with pyridine heterocyclic system. In this study, 2-Chloro-7-Methylquinoline-3-Carbaldehyde (ClMQC) molecule, which is a quinoline derivative, was selected and analyzed. Two minimum energies were found for the ClMQC at the theory level B3LYP/6-311++G(d,p). The energy difference (DE+ZPV) between the two conformers (ClMQC-1 and ClMQC-2) was calculated as 13.4 kJ mol^-1. Considering both conformers, the relative stability of the conformers was explained using the natural bond orbital (NBO) method and performed. Donor and acceptor pairs and orbital energies for NBO pairs were calculated by the Fock matrix equation. Orbital interactions were examined, and p-p* orbital interactions were found in the rings of the both conformers. Dominant orbital interactions of selected NBOs for ClMQC-1 and 2 were calculated at the theory level B3LYP/6-311++G(d,p) and plotted. From the calculations, the total stabilization energy difference between the two conformers was found to be 22.2 kJ mol^-1. The molecular electrostatic potential (MEP) surfaces of the two conformers were calculated by the DFT/B3LYP/6-311++G(d,p) method and drawn.