The Thermodynamics of Ionization of Anilinium Ions in Ethanol-Water Mixtures

✍ Scribed by W. van de Poel; P. J. Slootmaekers

• Publisher: Wiley (John Wiley & Sons)
• Year: 2010
• Weight: 446 KB
• Volume: 79
• Category: Article
• ISSN: 0037-9646
• DOI: 10.1002/bscb.19700790306

✦ Synopsis

Thermodynamic parameters of ionization of a number of substituted anilinium ions were measured in water and in ethanol-water mixtures at 25°C. Both the enthalpy and entropy of ionization show extreme values in a solvent mixture containing 0,90 mole fraction of water. Free energy values decrease smoothly and monotonically with increasing ethanol content o f the solvent. It is shown that the solvent effect is dependent on the nature of the substituent on the anilinium ion. The results are treated in terms o f the structural theory of water and o f ethanolwater mixtures. Furthermore, an attempt is made to determine the value of / I , the proportionality constant between AH,., and AS.,, , which was introduced by Hepler.