Ionic strength effect on deprotonation of para-sulfonatocalix[4]arene

Abstract

The deprotonation of para-sulfonatocalix[4]arene were studied by a combination of spectrophotometric and potentiometric methods at 25°C. The ionic strength of solutions was kept constant by sodium perchlorate as background electrolyte at 0.10 to 4.0 mol dm-3. Potentiometer was calibrated according to Gran method for each ionic strength. Spectral changes show evidence for proton dissociation of only one hydroxyl group of calixarene in the studied pH range of 2-10. The pKa values were calculated using STAR program by multivariate curve resolution of absorbance data. Results indicate that the acid-base behavior of para-sulfonatocalix[4]arene varies strongly with increasing ionic strength of solution. The dependence of deprotonation constants on ionic strength were explained by means of Specific ion Interaction Theory (SIT). Activity coefficients of species were modeled by a modified SIT approach. The specific ion interaction parameters were extracted associated with thermodynamic deprotonation constant of para-sulfonatocalix[4]arene

Solubility of Gliclazide in Transcutol + Water Co-solvent Mixtures at (298.15 to 333.15) K

“…29 Therefore, increased solubility of GLZ in co-solvent mixtures was probably due to reduced polarities. [27][28][29] The solubility data of GLZ in present study was in agreement with previous report of polarities. The highest mole fraction solubility of GLZ in pure Transcutol was probably due to the lowest polarity of Transcutol.…”

“…This was probably due to the reduced polarities in co-solvent mixtures as compared to pure water which is a highly polar solvent. 27 The lowest solubility of GLZ in pure water was also due to its highest polarity. 28 It is also very well reported in literature that the solubility of drug/solute molecules could be enhanced by reducing the polarity of solvents/co-solvent mixtures.…”

Mapping transition state structures for thiophosphinoyl group transfer between oxyanionic nucleophiles in water and aqueous ethanol solvents

“…One of the ways in which solvent polarity is measured is its dielectric constant. 42 In our earlier paper, 1 it was noted that the change of solvent from water ( ε = 78.6) 43 to a 70% water–30% ethanol mixture ( ε = 63.9), 43 Δ ε ∼ 15, slowed down the rates of the title reaction 14–320 times and made its TS looser in the aqueous ethanol solvent. With the acquisition of data in solvent mixtures with more ethanol content in this study, it is now possible to probe a little bit deeper into the effect of change of ε on the structure of the TS and, possibly, on the reaction mechanism, as the solvent polarity spectrum is spanned from pure water to 30% water–70% ethanol.…”

Anion Complexes with Tetrazine-Based Ligands: Formation of Strong Anion−π Interactions in Solution and in the Solid State

“…To get more information on solvent effects, the formation of anion complexes with the more soluble L2 ligand was also studied in the 80:20 (v/v) water/ethanol mixture, displaying a lower dielectric constant (ε = 69.05 at 25 °C) with respect to pure water (ε = 78.56 at 25 °C) . The stability constants of the complexes formed in the solvent mixture are listed in Table .…”