伯氨喹在乙醇—水混合溶剂中离解常数的测定及其与维生素C的配合比研究

DETERMINATION OF IONIZATION CONSTANTS OF PRIMAQUINE AND STUDY OF ITS COORDINATION RATIO WITH VITAMIN C

本文推导出用pH滴定法测定三元弱酸离解解常数的方程,测得25±0.01℃时,伯氨喹在乙醇—水的体积比为1:1的混合溶剂中,离子强度范围5×10^(-3)～5×10^(-2)mol/L时逐级离解常数为Ka_1=(3.84±2.35)×10^(-2)(归属于仲铵基),Ka_2=(1.50±1.17)×10^(-8)(归属于叔铵基),Ka_3=(2.07±0.27)×10^(-10)(归属于伯铵基)。并用pH法及电导法测得伯氨喹与维生素C在上述溶剂中的配合比为1:1。

Primaquine (P) has long been used as an antimalarial drug. The following formulas are derived for determination of the ionization constants of PH_3^(3+) by pH - titration method:in which K_w is the ionic product of water, a is the mole ratio of HClO_4 to primaquine and C_p is the total concentration of primaquine.The ionization constants of primaquine in 50% (v/v)ethanol in water determined at 25℃ in the ionic strength range of 5×10^(-3)～ 5× 10^(-2) mol/L are :Ka_1=( 3. 84±2. 35)× 10^(-2)(attributed to the secondary ammonium group of primaquine) ;Ka_2= (1.50±1.17 )× 10^(-8) (attributed to the tertiary ammonium group ) ;Ka_3= (2.07± 0.27 )× 10^(-10) (attributed to the primary ammonium group).The coordination ratio of primaquine to vitamin C in the above solvent is determined by continuous variation and mole ratio methods based on pH and conductance measurements to be 1 : 1, indicating that the coordination compound formed in the solution is mainly a 1 : 1 compound.