Solute-stationary phase interaction in gas liquid chromatography. Thermodynamic parameters for substituted...

Thermodynamic parameters were determined by variable temperature experiments on the gas liquid chromatography (GLC) relative retention values, log gamma, of 3- and 4-substituted halogenobenzene derivatives under non-polar condition. These deltadeltaHdegrees(s)(R,X) had a compensational relation with the deltadeltaSdegrees(s)(R,X) values. The free energy change deltadeltaGdegrees(s)(R,X) which is estimated from the deltadeltaHdegrees(s)(R,X) and the deltadeltaSdegrees(s)(R,X) at 298 K is less than -23 kJ x mol(-1). The deltadeltaSdegrees(s)(R,X) values could be explained by translational entropy change for the adsorbed active complex between the solute and stationary phase. It is suggested that the interaction could be mainly expressed by the physical adsorption exclusive of hydrogen bonding. The deltadeltaGdegrees(s)(R,X) values for each halogen derivative have been the excellent linear lines taking the same slopes for the monosubstituted benzene derivatives, deltadeltaGdegrees(s)(R,X). The regression analyses of their intercepts were given using the descriptor evaluated as the molecular volume sigmaa(X) rather than sigmaM(X). The regression analysis for polyhalogenobenzene was also given successfully using sigmaa(Xn).