Studies On Separation Of (R/S) Sec-Butyl Carboxylicayes And A Quantum Mechanical Stimulation

The separation of enantiomers of sec butyl carboxylicates on theβcyclodextrin derivatives chiral column had been studied by gas chromatography. The effect of sec butyl carboxylicates structure and column temperature on the separation of enantiomers of sec butyl carboxylicates had been investigated. On the other hand, the thermodynamic parameters in the process of separation of enantiomers on theβcyclodextrin derivatives chiral column (Cyclodex B and CycloSil B) were determined in order to discuss driven power in the process of separation of optical isomers. Chiral recognization mechanism of (R/S) BAA enantiomers on PMBCD was investigated. The experiment results showed that the separation factor (α) and separation degree (Rs) of sec butyl carboxylicates decreased when the chain size of carboxyl group increase. The separation degree of enatiomers of sec butyl acecate was best. There is excellent linear relationship between the logarithms of capacity factor (k′) and separation factor (α) of enantiomers of sec butyl carboxylicates and alkyl group parameters on the carboxyl group such asπand Es. And, the capacity factor (k′), the separation factor (α) and separation degree (Rs) of the enatiomers of sec butyl carboxylicates decreased with the increasing of the column temperature. It was demonstrated that the separation of enatiomers of sec butyl carboxylicates on theβcyclodextrin derivatives chiral column (Cyclodex B and CycloSil B) was enthalpy driven process and there was enthalpy entropy compensation.Host guest complexation of permethlatedβcyclodextrin (PMBCD) and with enantiomers of sec butyl acecates ((R/S) BAA) was simulated by Quantum Mechanics PM3 method. The Modeling results showed the stabilization complexation structures which formed with (R/S) BAA enantiomers and PMBCD were different. The stabilization energy of (R) BAA PMBCD complex was less than that of (S) BAA PMBCD. The chiral carbon in BAA for (R/S) BAA PMBCD complexes was closed to C(2) and C(3) in glucose unit. The former is stabler than the latter. The results correspond to the experimental findings from enantioselective gas chromatography.The structures and properties of the houst and the guest before and after inclusion,such as the size and shape of the houst cavity, the deformation energe of the guest molecular can be more significant changes, indicating that in the process of inclusion with CDs and (R/S) BAA enantiomers, the Van der Waals interaction plays an important role on the host guest inclusion process.