Selection of molecular descriptors used in quantitative structure-gas chromatographic retention relationships

Synthesis, antimicrobial evaluation and QSAR studies of novel piperidin-4-yl-5-spiro-thiadiazoline derivatives

In an attempt to find a new class of antimicrobial agents, a series of new 1,3,4-thiadiazolines were synthesized from 2,6-diarylpiperidin-4-ones, via the corresponding 4'-phenylthiosemicarbazones. All the synthesized compounds (23-39) were virtually screened against bacterial (Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi) and fungal strains (Candida albicans, Rhizopus sp, Aspergillus niger and Aspergillus flavus) by serial dilution method. QSAR study indicated that the increase in weakly polar component of solvent accessible surface area will favour antibacterial activity while increase in polarizability and decrease in ionisation potential and hydrogen bond donor will favour antifungal activity.

Theoretical analysis of the retention behavior of alcohols in gas chromatography

Quantitative structure-retention relationship (QSRR) models for the chromatographic (GC) retention times of alcohols on Superox 20M-diglycerol polarity stationary phase have been developed. Semi-empirical quantum chemical method (AM1) in MOPAC and Hartree-Fock (HF) method in Gaussian 98 implemented were employed to calculate a set of molecular descriptors of alcohols and ethyl acetate. Using multiple linear regression (MLR), we obtained the empirical functions with high correlation coefficient between retention times and quantum-chemical descriptors. The retention mechanism of alcohols of separation operating in the gas chromatogram was discussed. The results indicated that the QSRR models proposed were satisfactory.

Modeling chromatographic parameters by a novel graph theoretical sub-structural approach

A novel approach to the study of quantitative relationships between chromatographic parameters and the chemical structure is introduced. It is based on the computation of the spectral moments of the topological bond matrix by using different weights as diagonal entries of this matrix. The main advantage of the present approach is that the quantitative contributions of the structural fragments of molecules to the chromatographic parameters studied can be obtained explicitly. By using this approach we study two data sets: one composed of 156 alkanes and the other of 81 oxygen-containing organic molecules. In both cases excellent quantitative structure-chromatographic retention relationships were obtained. The contributions of the different fragments to the chromatographic retention were generated obtaining tables of additive contributions to the properties studied. The physicochemical interpretation of the results on the basis of the retention mechanisms is also analyzed in light of this new approach.