INFLUENCE OF pH WATER ON THE LIPOPHILICITY OF NICOTINIC ACID AND ITS DERIVATIVES INVESTIGATED BY RP-TLC

Abstract

Nicotinic acid (1) and its derivatives, namely methyl nicotinate (2), ethyl nicotinate (3), isopropyl nicotinate (4), butyl nicotinate (5), hexyl nicotinate (6), benzyl nicotinate (7), nicotinamide (8), N-methylnicotinamide (9), N,N-diethylnicotinamide (10), 3-pyridinecarboaldehyde (11), 3-pyridinecarbonitrile (12), 3-pyridylmethanol (13), and methyl 3-pyridyl ketone (14) were investigated with the use reversed-phase thin layer chromatography on RP-2 plates (Kieselgel 60 F254 silanisiert, E. Merck), and methanol – water (pHwater = 2.53; 5.88; 8.11) in different volume compositions as a mobile phase. The chromatographic parameters of lipophilicity (RMW(pH = 2.53); RMW(pH = 5.88); RMW(pH = 8.11)) of the studied compounds were determined and compared with both measured (logPexp), and calculated partition coefficients (AlogPs, IAlogP, ClogP, logPKowwin, xlogP, and miLogP). The lipophilicity RMW values correlate well with experimental partition coefficients (logPexp) for the compounds investigated. Best agreement was obtained with the experimental partition coefficients (logPexp) and the chromatographic parameter of lipophilicity RMW(pH = 5.88) for compounds investigated on RP-2 plates and by use of methanol + water (pHwater = 5.88) mobile phase. Chromatographic parameters of the lipophilicity correlated best with AlogPs. Moreover, ClogP correlated best with experimental partition coefficients (logPexp) of the compounds studied.