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Summary The behavior of 5,5-disubstituted hydantoin derivatives has been studied using four chromatographic systems, two normal-phase (silica gel stationary phase with ethyl acetate–toluene and acetonitrile–toluene mobile phases) and two reversed-phase (RP-18 systems with methanol–water and acetonitrile–water mobile phases). The effect of the structures of the derivatives on their retention in both normal and reversed-phase modes was investigated by use of QSRR and molecular descriptors. By means of multiple linear regressions results were interpreted in terms of understandable and physically meaningful variables. Among six models proposed, the two best were selected and tested for prediction of retention – one for normal-phase chromatography (NPC) and the other for reversed-phase chromatography (RPC). The most informative properties in the best NPC model, with similar effects on retention, are log P and valence connectivity indices. The informative properties in the best RPC model were log P and molecular weight, but the statistics was much worse than for NPC. Cross-validation indicated the best models are reliable QSRR models.

The chromatographic behavior of newly synthesized uracil derivatives has been studied by normal and reversed-phase thin-layer chromatography. Benzene-methanol, benzene-acetonitrile, and benzene-isopropanol were used as mobile phases in normal-phase chromatography and water-methanol and water-acetonitrile in reversed-phase chromatography. The mechanism of retention on different TLC supports was investigated. The retention constants determined for the uracils are discussed in terms of the physicochemical properties of both the solutes and stationary and mobile phases. R M 0 values derived by extrapolation from reversed-phase chromatography were correlated with the hydrophobicity log P calculated by use of the commercial program ACD/logP. In normal-phase chromatography values for C 0 (= R M 0 / n ) were correlated with the hydrophobicity log P . Good correlation was obtained for both types of chromatography. Retention constants R M 0 and C 0 can be used to express the lipophilicity of the compounds investigated.

The chromatographic behavior and mechanism of retention of some N-phenylsuccinimide derivatives has been studied. Retention constants were determined for normal- and reversed-phase TLC on silica gel and on silica gel impregnated with paraffin oil. Two lipophilic constants C 0 (calculated from normal-phase chromatography data) and R M,w (extrapolated RPC retention to 100% water as mobile phase) were derived, and partition coefficients between n-octanol and water, log P, were calculated by use of two different procedures - use of ACD/logP software and use of the interactive analysis log P predictor web site. Correlation between chromatographic lipophilic constants (C 0 or R M,w ) and log P values calculated by use of the different procedures has been studied. Results show that both R M,w and C 0 can be used as a measure of the lipophilicity of the compounds investigated.