1Chemistry Department, Islamic Azad University, Ashtian.
2Chemistry Department, Islamic Azad University, Arak.
3Chemistry Department, Shahid Beheshti University, Tehran, Evin.
*Corresponding author E-mail: f-gharib@cc.sbu.ac.ir
The protonation of different species of glycylisoleucine were studied in the pH range of 1.5–10 at 25°C using potentiometric technique. Investigations were performed in sodium perchlorate and tetraethylammonium iodide as background electrolytes at I (0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) mol dm−3. The parameters based on the protonation constants were calculated, and their dependences on ionic strength are described by a Debye-Huckel type equation. The dependence on ionic strength of the protonation constants was also analyzed by the specific ion interaction theory (SIT) model. The constants at infinite dilution, obtained using this model, are logK°1 = 2.72 and logK°2 = 8.24. The specific interaction coefficients are also reported.
Protonation constant, glycylisoleucine, ionic strength, thermodynamic value
