Agatino Casale

Ionic-strength dependence of formation constants. XII: A model for the effect of background on the protonation constants of amines and amino-acids

From analysis of literature data on the protonation of N-donor and N,O-donor ligands at 25 degrees , a simple model has been derived for the dependence of amine and amino-acid protonation constants on the background electrolytes, which takes into account the formation of weak complexes between the protonated forms of the amines (or amino-acids) and the background anions and between the amino-acid carboxylate group and alkali-metal cations.

Thermodynamic parameters for the formation of glycine complexes with magnesium(II), calcium(II), lead(II), manganese(II), cobalt(II), nickel(II), zinc(II) and cadmium(II) at different temperatures and ionic strengths, with particular reference to natural fluid conditions

Abstract Protonation constants and Mg 2+ , Ca 2+ , Pb 2+ , Mn 2+ -, Co 2+ , Ni 2+ , Cu 2+ , Zn 2+  and Cd 2+ glycine complex formation constants have been determined in different aqueous media at different temperatures. Salt effects are explained by a complex formation model which takes into account the formation of weak species. From the temperature dependence of the formation constants, thermodynamic parameters ΔH θ (and in some cases ΔC θ p ) have been obtained. A rigorous analysis of literature data, together with experimental findings, allows recommended formation parameters, in the ranges 0 ≤ I e ≤ 1 mol l −1 ( I e is the effective ionic strength) and 5°C ≤ T ≤ 45°C, to be obtained. Because the proposed model can be used in any electrolyte mixture in the above I and T ranges, the speciation in seawater, and other natural fluids, can be simulated by appropriate computer programs. The validity of the present approach which takes into account the ionic strength dependence of formation constants, together with the concepts of effective ionic strength and complex formation model, is discussed.

Complexing ability of pesticides and related compounds. Formation and stability in aqueous solution of H+, Li+, Na+, K+, Mg2+ and Ca2+ phenoxyacetate complexes at different temperatures and ionic strengths

Abstract The formation constants of Li + , N + , K + , Mg 2+ and Ca 2+ phenoxyacetate complexes were determined potentiometrically using an (H + )-glass electrode at 10, 25, 37 and 45°C, at several ionic strengths, in the range 0.04⩽ I ⩽ 0.9 mol 1 −1 . Simple empirical equations for the dependence of the formation constants on ionic strength were derived. From the temperature coefficients, estimates of Δ H o and Δ S o were obtained.

The effect of background on the protonation of pyridine: a complex formation model

Abstract The protonation constants of pyridine were obtained in aqueous solutions of LiCl, NaCl, NaClO 4 , NaNO 3 , NaI, KNO 3 , KI, RbCl, CsCl, MgCl 2 , CaCl 2 , tetramethylammonium iodide, tetraethylammonium iodide, tetramethylammonium chloride and tetraethylammonium chloride in the ranges 0 ⩽ I ⩽ 1 mol] −1 and 10 ⩽ T ⩽ 45 ° C. The differences in the protonation thermodynamic parameters of pyridine in the various solutions were interpreted in terms of weak species formation between the components.

Formation of ferrocyanides—IV: Th(IV), Nd(III), UO2(II) and Hg(II)

The stoichiometry of the reaction between ferrocyanide and thorium, neodymium, uranyl ion and mercury(II) has been investigated. The first three give single products irrespective of the order of addition of the reagents, but the last does not. If mercury(II) is added to ferrocyanide Hg(2)Fe(CN)(6) is obtained, but if ferrocyanide is added to mercury(II) various cyanide complexes of mercury are formed. The K(sp) values for the precipitates are reported.

Formation of ferricyanides-I silver(I), copper(II) and cadmium(II).

With potassium ferricyanide copper(II) forms KCu(10),[Fe(CN)(6)](7) quantitatively in 0.5M potassium nitrate medium. Cadmium forms Cd(3)[Fe(CN)(6)](2) if the ferricyanide is added to the cadmium solution in absence of extra potassium, and KCd(10)[Fe(CN)(6)](7) if potassium is added first, or if the cadmium solution is added to the ferricyanide. Silver forms Ag(3)Fe(CN)(6) only.

Sequestration of Alkyltin(IV) Compounds in Aqueous Solution: Formation, Stability, and Empirical Relationships for the Binding of Dimethyltin(IV) Cation by N- and O-Donor Ligands

The sequestering ability of polyamines and aminoacids of biological and environmental relevance (namely, ethylenediamine, putrescine, spermine, a polyallylamine, a branched polyethyleneimine, aspartate, glycinate, lysinate) toward dimethyltin(IV) cation was evaluated. The stability of various dimethyltin(IV) / ligand species was determined in NaClaq at t = 25°C and at different ionic strengths (0.1 ≤ I/mol L−1 ≤ 1.0), and the dependence of stability constants on this parameter was modeled by an Extended Debye-Hückel equation and by Specific ion Interaction Theory (SIT) approach. At I = 0.1 mol L−1, for the ML species we have log K = 10.8, 14.2, 12.0, 14.7, 11.9, 7.7, 13.7, and 8.0 for ethylenediamine, putrescine, polyallylamine, spermine, polyethyleneimine, glycinate, lysinate, and aspartate, respectively. The sequestering ability toward dimethyltin(IV) cation was defined by calculating the parameter pL50 (the total ligand concentration, as −log CL, able to bind 50% of metal cation), able to give an objective representation of this ability. Equations were formulated to model the dependence of pL50 on different variables, such as ionic strength and pH, and other empirical predictive relationships were also found.

Complexing ability of pesticides and related compounds. thermodynamic parameters for the formation of H+, Na+ and Ca2+ complexes with 2,4-dichlorophenoxyacetate in aqueous solution at different temperatures and ionic strengths

Abstract The formation constants of 2,4-dichlorophenoxyacetate for H+, Na+ and Ca2+ complexes were determined pH-metrically at 10, 25 and 45°C in the ionic strength range 0.05 ⩽ I ⩽ 1 mol 1−1. The dependence of formation constants on ionic strength and temperature was taken into account by empirical equations and estimates of ΔHXXX were obtained. Comparisons with the stability of similar carboxylate complexes are made.

Formation of nickel, cobalt, manganese and cadmium ferrocyanides

Potentiometric and solubility studies have been made of the ferrocyanides of nickel, cobalt, manganese(II) and cadmium both in the presence and absence of potassium. The K(3p),DeltaG degrees , DeltaH degrees and DeltaS degrees values are reported.

Formation of ferrocyanides—III Fe(III), La(III) and Ce(III)

Potassium ferrocyanide forms Fe(4)[Fe(Cn)(6)](3) with Fe(III), KLaFe(CN)(6) with La(III) and KCeFe(CN)(6) with Ce(III). The thermodynamic data for the two lanthanide compounds have been determined.