Reactivities of Radiation-protective Aminoalkylisothiuronium Salts. III. Reactivities of 2-Aminoethyl- and 3-Aminopropylisothiuronium Salts

抄録

The potentiometric titration of radiation-protective aminoalkylisothiuronium salt, such as AET or APT, was carried out in various conditions with a recording titrator. The method for the selective determination of each component in the mixtures containing the isothiuronium salt, the transguanylation and cyclization products was established first. By using this technique, it was clarified that AET was mainly transguanylated and partly cyclized during the titration and that the molar ratio of those two reaction products depends on the titration speed and temperature. APT was transguanylated nearly quantitatively without repsect to the titration speed. Both reactions may proceed through the ionized isothiuronium salt. The rate of the transguanylation was extremely fast. In the presence of 0.5 equivalent alkali, the degree of the transguanylation at 25° was as follows ; AET : 0.77 in 0.5 min, 0.94 in 2 min, APT : 0.82 in 0.5 min, 0.94 in 2 min. The pH dependence of the transguanylation was postulated and discussed quantitatively.