The kinetics of water replacement in the complex [Pd(Et4dien)(H2O)](NO3)2, where Et4 dien = Et2N[CH2]2NH[CH2]2 NEt2, by thiourea and its methyl, ethyl, n-butyl, N, N′-dimethyl, N, N′-diethyl, N, N′-di-n-butyl and p-tolyl derivatives have been studied at 25 °C and ionic strength 0.03 mol dm–3 in water and in the presence of cationic (CTAN) and anionic (SDS) micelle-forming surfactants. All the reactions studied are first order with respect to both reactant species. The reaction rates in water depend on both the steric hindrance and the inductive effects of the alkyl groups present in the parent thiourea molecule. The substitution reactions are inhibited by the CTAN micelles and take place in the bulk water, the nucleophiles being partitioned between the aqueous and micellar pseudo-phases. Anionic SDS micelles accelerate the overall reactions, which occur in the micellar phase with the same mechanism as in water. The estimated binding constants of the nucleophiles are larger with CTAN micelles than with SDS micelles and depend on the hydrophobic nature and number of the alkyl groups present in the unsubstituted thiourea. In the case of the CTAN surfactant the standard transfer free energies of the thioureas from water in the micelle suggest that binding of the solubilizates occurs in the palizade layer of the micelle.
硫脲及其甲基在[Pd(Et4 dien)(
H2O)](
NO3)2 复合物(其中 Et4 dien = Et2N[CH2]2NH[CH2]2 NEt2)中的
水置换动力学、研究了
硫脲及其甲基、乙基、正丁基、N,N′-二甲基、N,N′-
二乙基、N,N′-二正丁基和
对甲苯基衍
生物在 25 °C 和离子强度 0.03 mol dm-3 的
水中,并在阳离子(CTAN)和阴离子(
SDS)胶束形成表面活性剂存在下进行了研究。所研究的所有反应对于两种反应物都是一阶反应。
水中的反应速率取决于母
硫脲分子中存在的烷基的立体阻碍和感应效应。取代反应受到 CTAN 胶束的抑制,在大体积
水中进行,亲核物在
水相和胶束假相之间分配。阴离子
SDS 胶束加速了整个反应,这些反应在胶束相中发生的机理与在
水中发生的相同。与
SDS 胶束相比,CTAN 胶束与亲核物的估计结合常数更大,并且取决于未取代的
硫脲中存在的烷基的疏
水性和数量。就 CTAN 表面活性剂而言,胶束中的
硫脲与
水的标准转移自由能表明,
增溶剂的结合发生在胶束的胶束层中。