Chromatographic behaviour and lipophilicity of some benzimidazole derivatives

The retention behaviour of 2-amino-5,6-dimethylbenzimidazoles, 2-aminobenzimidazoles, and 5,6-dimethylbenzimidazoles has been studied on thin layers of rice starch, cellulose, and Aminoplast. The mobile phases used were cc ammonia-n-propanol, 40 + x, x = 1-9 (v/v) for cellulose and rice starch layers and cyclohexane-acetone-cc ammonia, 40 + x + 0.5; x = 2-14 (v/v) for on Aminoplast layers. Normal-phase chromatography occurred on Aminoplast layers whereas reversed-phase chromatography was obtained on cellulose and rice starch layers. Determination of lipophilicity by TLC is mainly based on the linear relationship between R-M values and the concentration of organic solvent in the mobile phase, in accordance with well known TLC equations. Retention constants, R-M(0), were determined by extrapolation. Good correlation was found between the retention constants, R-M(0), and logP, and between R-M(0) and the biological activity of the compounds investigated.