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

Yang, Bin; Li, Zhongjian; Lei, Lecheng; Sun, Feifei; Zhu, Jingke

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

2016

Yang, Bin | Li, Zhongjian | Lei, Lecheng | Sun, Feifei | Zhu, Jingke

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.

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