Protonation Constants, Activity Coefficients, and Chloride Ion Pair Formation of Some Aromatic Amino-Compounds in NaCl_aq(0 mol·kg^–1 ≤ I ≤ 3 mol·kg^–1) at T = 298.15 K

Abstract

The protonation constants of five structurally different aromatic amino-compounds [1,2-phenylenediamine (L1), 4-N-(2-hydroxyethyl)2,4-diaminoanisole (L2), 2-(2,4-diaminophenoxyethanol) (L3), 4-5-diamino-1-N-(2hydroxyethyl)pyrazole (L4), 1,3-bis(2,4-diaminophenoxy)propane (L5)] obtained by potentiometric measurements in NaCl (aq) (0 mol•kg −1 ≤ I ≤ 3 mol•kg −1 ) at T = 298.15 K, are reported. The Debye−Huckel, SIT (Specific ion Interaction Theory),and Pitzer type equations were used to determine the parameters for the dependence of the protonation constants on ionic strength and to calculate the specific interaction coefficients of the ionic species, as well as the protonation constants at infinite dilution. Distribution measurements were also carried out at different ionic strengths in 2-methyl-1-propanol/aqueous solution mixtures to obtain the distribution coefficients of the aromatic-amino compounds. The Setschenow coefficient and the activity coefficient of the neutral species were calculated by using a simple approach from distribution data. The dependence on salt medium was also explained in terms of weak polyammonium cation−chloride complexes.

Solubility and modeling acid–base properties of adrenaline in NaCl aqueous solutions at different ionic strengths and temperatures

“…399 By using similar procedures, the dependence of the protonation 400 constants on the ionic strength was also investigated; Fig. 4 reports 401 the distribution of the species at I = 0.15, 0.50 and 1.0 mol L À1 , and 402 at T = 310.15 K. The dependence of the protonation constants on 403 the ionic strength can be explained, as already reported in many 404 works, namely in terms of weak ion pairs formation, between the 405 charged ligand species and the ions of the supporting electrolytesBretti et al, 2012a; Daniele et alBattaglia et al, 2008;Bretti et al, 2008aBretti et al, , 2013Bretti et al, , 2012b Bretti et al, , 410 2012cBretti et al, , 2005Bretti et al, , 2006aCrea et al, 2012), the Setschenow coefficients 411 were calculated both in the molar and the molal concentration…”

Thermodynamic Study on the Protonation and Complexation of GLDA with Ca2+and Mg2+at Different Ionic Strengths and Ionic Media at 298.15 K

“…Another model to explain this difference is taking into account the formation of weak ion pairs; this model has been used in other papers and its theory can be found in many refs. 18,36 Briefly, we choose, a baseline electrolyte (in this case (C 2 H 5 ) 4 NI (aq) ) that do not form ion pairs with the species of ligand and moreover we consider that the activity coefficients of the species in the baseline electrolyte are similar to the interacting electrolyte, corrected for ion-pair formation, these assumptions are appropriate at relatively low ionic strength values and for low molecular weight ligands. This model 34 depends only on the stoichiometry and the charges in the formation reaction:…”

Unique binding behaviour of water-soluble polycationic oxacalix[4]arene tweezers towards the paraquat dication

“…15 However, given that ammonium ions are known to bind to chloride counterions even in water, 13,16 it is reasonable to envisage that ion-paired species may contribute, to some extent, to oxacalixarene/paraquat binding, beyond mere Coulombic shielding, by means of -NH 3 + Á Á ÁCl À Á Á ÁPQT 2+ interactions. For easier comparison between NMR and UV-Vis data, throughout the manuscript pD values are reported as the corresponding pH values.…”

“…For easier comparison between NMR and UV-Vis data, throughout the manuscript pD values are reported as the corresponding pH values. 13 ¶ Neutral aromatic hydrocarbons (e.g., naphthalene, anthracene, pyrene, etc.)…”

“…Chloride anions most probably reduce the electrostatic screening distance, allowing for attractive host-guest interactions to overcome Coulombic repulsion between cationic 1Á3H + and PQT 2+ rings. 15 However, given that ammonium ions are known to bind to chloride counterions even in water, 13,16 it is reasonable to envisage that ion-paired species may contribute, to some extent, to oxacalixarene/paraquat binding, beyond mere Coulombic shielding, by means of -NH 3 + Á Á ÁCl À Á Á ÁPQT 2+ interactions. The active role played by Cl À was confirmed by 1ÁnHCl/PQTÁ2Cl competitive binding experiments carried out in the presence of HBr, CF 3 COOH or HClO 4 in excess.…”