Ionization Constants of 2-Aminoethyl-and 3-Aminopropyl-isothiuronium Salts and Their Transformation Products

抄録

The ionization constants of 2-aminoethylisothiuronium (AET) and 3-aminopropylisothiuronium (APT) salts, dibasic acid intrinsically, were determined potentiometrically. Those isothiuronium salts were extremely unstable and underwent the transguanylation, during the titration, through the conjugate base to the sulfhydryl compounds, which were ionized in the second step. For the determination of the ionization constant, the titration curve was treated as an equimolar mixture containing two acids. From the temperature dependence of the ionization constant, measured at 5°, 15°, 25° and 35°, was calculated the enthalpy of the ionization, which led to the evaluation of the entropy. The thermodynamic functions of those compounds at 25° were as follows : [table] The thermodynamic functions for the transguanylation and the cyclization products from those isothiuronium salts were also determined.