Theoretical Study Of Chiral Discrimination In Fluorinated Chiral Molecule

The chiral discrimination based on small molecule hydrogen-bonded complexes is very importance in life sciences and asymmetric organocatalysis. Chiral discrimination forces and energies are central for understanding and determining the mechanism of chiral discrimination. Fluorine substitution imparts unique and advantageous physio-chemical properties that can be employed to constructively alter pharm acological agents. However, such an experimental and theoretical study is still highly challenging for larger system. The research on the chiral discrimination base on small fluorinated chiral molecule has received significant attention in recent years.In this study, the geometrical optimizations were carried out using Second-order M?ller-Plesset perturbation theory (MP2). The NBO method was used to study the bonding-antibonding orbital interactions. The king of interactions has been described to be the responsible of the stabilization in hydrogen-bonded complexes. The most important work and results are as follows:(1) The study system was the hydrogen bond complex of the chiral molecule 2–fluorooxirane (FO) with hydrogen peroxide. The geometrical optimizations and energy analysis were carried out using Second-order M?ller-Plesset perturbation theory (MP2). The relationship and distinction among the 2-fluorooxirane, 2-methylol oxirane and 2-methyl oxirane were also shown. These data indicate that the chiral discrimination ability of FO···HOOH was larger than that of PO···HOOH as expected, but smaller than that of M-olOx···HOOH. Somewhat unexpected, only–O– is the main interaction point and the–F is not a hydrogen bond acceptor in the four most stable complexes. To understand the trend observed for the chirodiastaltic energies, we used"through-space"interactions introduced by Portmann et al. to examine distinct contributions to the interactions of FO with HOOH. The result indicate that the mechanisms of chiral discrimination in FO, M-olOx and PO···EtOH were different. The forces at play in chiral discrimination of FO···HOOH are secondary electrostatic interactions. For M-olOx···HOOH, the primary hydrogen bonds are responsible for chiral discrimination, and pervious resport [7] has given conclusion that the concerted effect of secondary hydrogen bond interactions and steric hindrance that seems to govern the discrimination process in the chiral discrimination of PO···EtOH. Finally, the harmonic frequencies, IR intensities, rotational constants and dipole moments for the complexes were also presented to assist future spectroscopic investigation.(2)We also extend chiral discrimination of the 2-methylol oxirane (M-olOx) and hydrogen peroxide formed the hydrogen bond complexes and study chiral discrimination for the hydrogen-bonded complexes 2-methylol oxirane (M-olOx) with 2-Fluoroethanol(FE). Eighteen complexes of M-olOx···FE have been identified. The–F is not a hydrogen bond acceptor in the four most stable complexes. Only 9 structures emerged which contained C-F···H-C bond. The H-F distances in the study emerged >2.5 ? which is close to the sum of the van der Waals radii of hydrogen and fluorine. In order to further systematic and comprehensive analysis of the role of fluorine atoms, we also present an ab initio investigation on 2-methylol oxirane (M-olOx) with ethanol. Fluorine substitution imparts in ethanol increasing the role-point in the intermolecular; hence, the intensity was enhanced.