Prediction of Setschenow constants of N-heteroaromatics in NaCl solutions based on the partial charge on the heterocyclic nitrogen atom

The solubilities of 19 different kinds of N-heteroaromatic compounds in aqueous solutions with different concentrations of NaCl were determined at 298.15 K with a UV-vis spectrophotometry and titration method, respectively. Setschenow constants, K s , were employed to describe the solubility behavior, and it is found that the higher ring numbers of N-heteroaromatics gave rise to the lower values of K s . Moreover, K s showed a good linear relationship with the partial charge on the nitrogen atom ( Q N ) for either Q N  > 0 or Q N  < 0 N-heteroaromatics. It further revealed that Q N was well-matched in the prediction of salting-out effect for N-heteroaromatics compared to the conventional descriptors such as molar volume ( V H ) and the octanol-water partition coefficient ( K ow ). The heterocyclic N in N-heteroaromatics may interact with Na + ions in NaCl solution for Q N  < 0 and with Cl − for Q N  > 0.