The alkaline hydrolysis of p-nitrophenyl acetate (p-NPA) in 1.0mol dm−3 NaOH at 25 °C was almost completely retarded by the addition of a binuclear Cu(II) complex with α-cyclodextrin (Cu2α-CD). The dissociation constant for an inclusion complex of Cu2α-CD with p-NPA was determined to be 0.059 mmol dm−3, which is about one 200th that for an inclusion complex of α-CD with p-NPA. The alkaline hydrolysis of o- and m-nitrophenyl acetates was also retarded by Cu2α-CD, though the extent of retardation was much less than that for p-NPA. A binuclear Cu(II) complex with β-cyclodextrin (Cu2β-CD) also caused a stereoselective deceleration of the alkaline hydrolysis of the esters. However, the stereoselectivity of Cu2β-CD was not so remarkable as that of Cu2α-CD. Dissociation constants for inclusion complexes of Cu2α2-CD with several alcohols and other organic substrates were determined by the kinetic examination of the competitive inhibition effect of the substrates on the association of Cu2α-CD with p-NPA. Cu2α-CD formed stable inclusion complexes with such disk-like molecules as cyclohexanol, cycloheptanol, and p-nitrobenzyl alcohol. The geometry of a Cu2α-CD-p-NPA inclusion complex was presumed on the basis of these results.
对硝基苯乙酸酯(p-NPA)在 1.0mol dm-3 NaOH 溶液(25 °C)中的碱性
水解几乎完全被加入α-
环糊精(Cu2α-CD)的双核 Cu(II)络合物所延缓。经测定,Cu2α-CD 与 p-NPA 的包合络合物的解离常数为 0.059 mmol dm-3,约为α-CD 与 p-NPA 的包合络合物解离常数的 200 分之一。Cu2α-CD 也能延缓邻
硝基苯乙酸酯和间
硝基苯乙酸酯的碱性
水解,但延缓程度远小于
对硝基苯酚的延缓程度。Cu(II) 与 β-
环糊精的双核配合物(Cu2β-CD)也会导致
酯类碱性
水解的立体选择性减速。不过,Cu2β-CD 的立体选择性不如 Cu2α-CD 那么显著。通过对底物对 Cu2α-CD 与 p-NPA 结合的竞争性抑制作用进行动力学检验,确定了 Cu2α2-CD 与几种醇和其他有机底物的包合复合物的解离常数。Cu2α-CD 与
环己醇、
环庚醇和
对硝基苯甲醇等盘状分子形成了稳定的包合物。根据这些结果推测了 Cu2α-CD-p-NPA 包合物的几何形状。