Abstract
The determination of the proton ionization constant of N'-methyl-2-aminoethyl-isothiuronium (N'-methyl-AET) was attempted. This compound was also transguanylated, as in AET, during the potentiometric titration. The first conjugate base of N'-methyl-AET is relatively stable and subsequently ionized to the second base with its rapid transguanylation to the sulfhydryl compound. The first ionization is due to amino group, pK 8.05 and ΔH 12 kcal/mole, and the second is due to isothiuronium group, pK 9.88 and ΔH 18 kcal/mole. The reactivity of two conjugate bases of N'-methyl-AET was discussed.
