Benesi-Hildebrand (B-H) method is a widely used approach for determining the stoichiometry and equilibrium constants of nonbonded interactions, particularly 1∶1 and 1∶2 interactions. Using computer simulation, it was shown that, under certain conditions, the approach could generate inappropriate stoichiometric conclusions for 1∶2 interactions. This problem could occur in the cases of both weak and strong interactions, where the 1∶1 B-H plots showed a linear feature and the 1∶2 B-H plots showed a nonlinear feature. In addition, effect of the initial concentrations on the accurate evaluation of equilibrium constants of 1∶1 interactions was investigated. It was found that the minimum safe concentration ratio r0 between ligand and central species was 100. However, for weak nonbonding interactions, for example K＜ 25 L·mol-1 (C0P=4×10-4 mol· L-1), the ratio r0 has no limitation. Two conditions proposed in literatures for the safe application of the B-H method were examined. It was found that the inequation, 1/(KC0P) ≥ 10, was a condition to secure CB/C0B＞91%. The other inequation, KC0B＞0.1, was not found to be the safe condition to validate the B-H method.%Benesi-Hildebrand(B-H)方程现被广泛地应用于各种非键作用体系,特别是作用比为1∶1型和1∶2型的体系.该方程可以用来确定作用体系的平衡常数以及作用比.通过计算机模拟,发现在某些情况下,对于1∶2型的作用体系,B-H方程会给出错误的作用比信息.无论是弱的作用体系还是强的作用体系,都可能会出现1∶1的B-H方程曲线呈现出线性,同时(或者)1∶2的B-H方程曲线呈现出非线性的情况.此外,本文还研究了体系中两种作用物质的初态浓度比对于1∶1型作用的平衡常数计算的影响,发现最小的初态浓度比(r0)等于100是可以确保B-H方程近似条件C0B≈CB成立的安全阈值.当作用很弱的时候,比如说作用的平衡常数K小于25 L·mol-1(C0P=4×10-4 mol·L-1)时,则不需要对最小初态浓度比值r0进行限制,就可以满足B-H方程的近似条件.通过计算机模拟还分析了文献中提出的两个边界条件.研究表明1/(KC0P)≥10可以保证处于平衡状态时的CB/C0B≥0.91.而另一个条件KC0B＞0.1并不是确保B-H方程近似条件成立的充分条件.
展开▼
