General Analytical Procedure for Determination of Acidity Parameters of Weak Acids and Bases

Table 7

The p’s values of compounds determined in the multicomponent mixture of amino acid, heterocyclic moiety, and weak (Mes) and strong (HCl) acids at 25°C.

Composition of D	p	pKHis ±	pKPy3CA	pKMes	pKImH
L-His	pK3	9.67 ± 0.01	—	—	—
L-His + HCl (1 : 1)	pK2	6.28 ± 0.01	—	—	—
	pK3	9.97 ± 0.01	—	—	—
L-His + HCl (1 : 2)	pK1	1.54 ± 0.04	—	—	—
	pK2	6.26 ± 0.01	—	—	—
	pK2	9.66 ± 0.01	—	—	—
L-His + Py3CA+; + Mes + ImH	pK1	—	—	6.28^*	7.56^*
	pK2	6.28^*	4.68 ± 0.24	—	—
	pK3	10.06 ± 0.55	—	—	—
L-His + Py3CA +; + Mes + ImH + HCl	pK1	—	4.81 ± 0.28	6.07 ± 0.14	7.49 ± 0.05
	pK2	6.43 ± 0.74	—	—	—
	pK3	10.06 ± 0.37	—	—	—
Composition of D	p	pKAla	—	—	—
L-Ala	pK2	10.30 ± 0.01	—	—	—
L-Ala + HCl (1 : 1)	pK1	2.25 ± 0.01	—	—	—
	pK2	10.25 (0.07)	—	—	—

 ^*p value const. from the literature [see Table 11].