caa a22 4500 378927418 CHVBK 20180305123621.0 cr unu---uuuuu 161128e20041101xx s 000 0 eng 10.1524/ract.92.9.575.54970 doi (NATIONALLICENCE)gruyter-10.1524/ract.92.9.575.54970 Protonation and complexation of isosaccharinic acid with U(VI) and Fe(III) in acidic solutions: potentiometric and calorimetric studies [Elektronische Daten] [Linfeng Rao, Alexander Yu. Garnov, Dhanpat Rai, Yuanxian Xia, Robert C. Moore] Protonation and complexation of α-isosaccharinic acid with U(VI) and Fe(III) have been studied in acidic solutions at t=25°C and I=1.0mol dm-3 NaClO4. From the potentiometric titrations, the protonation constant of the carboxylate group is calculated to be 3.65±0.05 and the data are consistent with the presence of three and four successive mononuclear complexes for U(VI) and Fe(III), respectively. The formation constants of the complexes, log βj for the reactions of M+L=MLj where j=1-3 for U(VI), j=1-4 for Fe(III) and L stands for isosaccharinate, are determined to be 2.91±0.15 (UO2L), 5.37±0.07 (UO2L2), 7.25±0.18 (UO2L3), 5.06±0.17 (FeL), 8.51±0.15 (FeL2), 11.00±0.16 (FeL3), and 12.99±0.17 (FeL4). From the calorimetric titrations, the enthalpy of protonation of the carboxylate group is determined to be -(7.94±0.03)kJ mol-1, similar to that of other α-hydroxycarboxylates. The enthalpies of complexation between U(VI) and isosaccharinate are quite small: Δ H1 = -(1.0±1.0)kJ mol-1, Δ H2=1.4±1.8kJ mol-1 and Δ H3=-(6.2±3.0)kJ mol-1, typical of the interactions between carboxylates and hard-acid cations. The complexation between U(VI) and isosaccharinate is mainly entropy-driven. In comparison, the enthalpies of complexation for FeL3 and FeL4 are large and exothermic, contributing significantly to the stability of the complexes. © 2004 Oldenbourg Wissenschaftsverlag GmbH Laboratory techniques, experiments nationallicence Analytical chemistry nationallicence Inorganic chemistry nationallicence Rao Linfeng aut Garnov Alexander Yu aut Rai Dhanpat aut Xia Yuanxian aut Moore Robert C. aut Radiochimica Acta/International journal for chemical aspects of nuclear science and technology Oldenbourg Wissenschaftsverlag GmbH 92/9-11/2004(2004-11-01), 575-581 0033-8230 92:9-11/2004<575 2004 92 ract https://doi.org/10.1524/ract.92.9.575.54970 text/html Onlinezugriff via DOI 1 research article jats NATIONALLICENCE 856 40 https://doi.org/10.1524/ract.92.9.575.54970 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Rao Linfeng aut NATIONALLICENCE 700 1- Garnov Alexander Yu aut NATIONALLICENCE 700 1- Rai Dhanpat aut NATIONALLICENCE 700 1- Xia Yuanxian aut NATIONALLICENCE 700 1- Moore Robert C. aut NATIONALLICENCE 773 0- Radiochimica Acta/International journal for chemical aspects of nuclear science and technology Oldenbourg Wissenschaftsverlag GmbH 92/9-11/2004(2004-11-01), 575-581 0033-8230 92:9-11/2004<575 2004 92 ract CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-gruyter