Rais Jirí, Okada Tatsuhiro, Alexova J
Nuclear Research Institute plc Rez, 25068 Rez, Czech Republic, and National Institute of Advanced Industrial Science and Technology, Higashi 1-1-1, Central 5, Tsukuba, Ibaraki 305-8565, Japan.
J Phys Chem B. 2006 Apr 27;110(16):8432-40. doi: 10.1021/jp060318z.
Thermodynamic standard Gibbs energies of transfer of alkali metal cations related to Cs+ cation [DeltatG degrees*,(Cs+)-[DeltatG degrees*,(M+)] between several mutually saturated solvents of the type water-solvent were calculated from determined extraction exchange constants Kexch degrees,(Cs+/M+). The used liquid-liquid extraction method with radioactive tracing by 137Cs permits attaining higher precision of the values as compared to the methods used up to now. The data for o-nitrophenyloctyl ether, 1,2-dichloroethane, and 1-octanol were compared with literature sources and recommended absolute values of DeltatG degrees,M+) are reported. For dissociating solvents, the dependences of [DeltatG degrees,(Cs+) - [DeltatG degrees,(M+)] on Gibbs energy of hydration of an ion, DeltaGhydr degrees are straight lines either for four cations Cs+, Rb+, K+, and Na+ (nitrosolvents) or for three cations Cs+, Rb+, and K+ (1,2-dichloroethane and 1-octanol). The hydration of Na+ and still more of Li+ in the water-saturated organic phase is apparent from the results. This manifests for high-water-content equilibrium 1-octanol even in a reversal of the values [i.e., DeltatG degrees*,(Li+) being more negative than DeltatG degrees,(Na+)], although for Cs+, Rb+, and K+, the general trend is conserved. Water-saturated 1-octanol is thus slightly less basic than water, but the overall selectivity is very low. For one studied nondissociating solvent, dioctyl sebacate, the trend of the dependences of log Kexch degrees,(CsB/M+) on DeltaGhydr degrees is similar to that of Kexch degrees,*(Cs+/M+) for polar solvents, but different for different anions B, thus reflecting ion association in the organic phase.
根据测定的萃取交换常数(K_{exch}^{\circ},(Cs^{+}/M^{+}))，计算了在几种水 - 溶剂类型的互饱和溶剂之间，与(Cs^{+})阳离子相关的碱金属阳离子转移的热力学标准吉布斯自由能([\Delta_{t}G^{\circ}{*,(Cs^{+})}-\Delta{t}G^{\circ}{*,(M^{+})}])。与目前使用的方法相比，所采用的用(^{137}Cs)进行放射性示踪的液 - 液萃取方法能够获得更高精度的值。将邻硝基苯基辛基醚、1,2 - 二氯乙烷和1 - 辛醇的数据与文献资料进行了比较，并报告了推荐的(\Delta{t}G^{\circ}{*,(M^{+})})的绝对值。对于离解溶剂，对于四种阳离子(Cs^{+})、(Rb^{+})、(K^{+})和(Na^{+})（亚硝基溶剂）或三种阳离子(Cs^{+})、(Rb^{+})和(K^{+})（1,2 - 二氯乙烷和1 - 辛醇），([\Delta{t}G^{\circ}{*,(Cs^{+})}-\Delta{t}G^{\circ}{*,(M^{+})}])对离子水合吉布斯自由能(\Delta G{hydr}^{\circ})的依赖关系是直线关系。从结果可以明显看出，在水饱和有机相中(Na^{+})以及更明显的(Li^{+})的水合作用。即使在水含量高的平衡态1 - 辛醇中，这也表现为数值的反转（即(\Delta_{t}G^{\circ}{*,(Li^{+})})比(\Delta{t}G^{\circ}{*,(Na^{+})})更负），尽管对于(Cs^{+})、(Rb^{+})和(K^{+})，总体趋势是保持的。因此，水饱和的1 - 辛醇的碱性略低于水，但总体选择性非常低。对于一种研究的非离解溶剂癸二酸二辛酯，(\log K{exch}^{\circ},(CsB/M^{+}))对(\Delta G_{hydr}^{\circ})的依赖关系趋势与极性溶剂中(K_{exch}^{\circ},(Cs^{+}/M^{+}))的趋势相似，但对于不同的阴离子(B)有所不同，从而反映了有机相中的离子缔合。
