Abstract:

Based on the order rule for substituents on a chiral carbon atom, a novel structural parameter, the molecular chiral index (wj ), was investigated in this paper. A quantitative structure-retention index relationship (QSRR) between the retention index (RM) froma chiral thin-layer chromatogramfor 18 chiral organic acids (8 hydroxyl acids and 10 amino acids) and wj, an electrotopological state index for atom types (En) was investigated using multivariate statistical regression. Using leaps-and-bounds regression analysis, an optimal four-parameter QSRR model was set up. The traditional correlation coefficient (R2) and the cross-validation correlation coefficient (Q2) of the leave-one-out (LOO) method were 0.969 and 0.943, respectively. Results demonstrate that the model is highly reliable and that statistically it has a good predictive ability. From the four parameters (wj, E13, E16, E17) of the model, the two-dimensional molecular structure characteristics (such as =O,—OH, —NH2) and the chiral characteristics are shown to be decisive factors that affect the retention index for the chiral organic acids. Results also show that the new parameters wj and En are rational and efficient in the determination of retention indices of chiral organic acids. Therefore, this paper provides an effective method to predict the retention indices of chiral organic acids.

Key words: Hydroxyl acid, Amino acid, Retention index, Chiral index, Electrotopological state indices for atomtype, Multivariate regression analysis