||Interaction of Water with Organic Solute Species.
Liott, Charles L. ;
Hopkins, Jr, H. P. ;
Perdu, M. ;
||Georgia Inst. of Tech., Atlanta. Environmental Resources Center.
||ERC-1473; DI-14-31-0001-3269; OWRR-B-049-GA; 03762,; B-049-GA(10)
Organic ions ;
Thermochemical properties ;
Gibbs free energy ;
Anilinium compounds ;
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The report describes a detailed investigation of the relative contributions of the enthalpy and entropy of ionization to the Giggs free energies of ionization of substituted anilinium ions, pyridinium ions, and theiphenol. Enthalpies of ionization were determined calorimetrically in aqueous solution at 25C. Entropies of ionization were calculated from the experimental enthalpies and literature Gibbs free energies of ionization. In the case of thiophenol, the Gibbs energy was calculated from the pKa, which was determined spectrophotometrically in a standard buffer solution. The experimental data for substituted anilinium ions and pyridinium ions were also analyzed in terms of Hepler's theory of substituent effects. Theoretical and mechanistic explanations are discussed.