Complete resolution of the ionization equilibria of 5-deoxypyridoxal in water-dioxane mixtures

Llor, Juan; Ros, Maria P.; Asensio, Salvador B.

doi:10.1007/bf02768827

Cited by 9 publications

(4 citation statements)

References 18 publications

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“…Temperature effects on microscopic ionization equilibria have rarely been investigated. To our knowledge, only limited information on diprotic hydroxypyridines is available so far. − The generalization of the cluster approach to include temperature effects should enable us to perform this type of analysis in more complex situations. The present approach explores a similar interpretation of enthalpy effects in surfactant binding .…”

Section: Introductionmentioning

confidence: 99%

Resolution of Microscopic Protonation Enthalpies of Polyprotic Molecules by Means of Cluster Expansions

2012

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Cluster expansion techniques are used to obtain microconstants and microenthalpies of protonation reactions. The approach relies on the analysis of macroscopic protonation constants and protonation enthalpies within a homologous series. Various linear aliphatic polyamines are considered, including 3,4-tri (spermidine), 3,4,3-tet (spermine), and 2,2,2,2-pent. Besides the full resolution of the microscopic protonation equilibria, one obtains information on the temperature dependence of the microstate probabilities. We find that the concentrations of the dominant microspecies increase with increasing temperature. Due to the large negative protonation enthalpies that are typical for amines, higher temperatures generally favor the less protonated species.

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Section: Introductionmentioning

confidence: 99%

Resolution of Microscopic Protonation Enthalpies of Polyprotic Molecules by Means of Cluster Expansions

2012

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“…Here, the acid dissociation constants (p K a ) play an important role. Decreasing the solvent’s polarity while increasing 1,4-dioxane, it is well known that the p K a s of substituted amines − and N-containing heterocycles , decreases in number. The same trend was observed in our DFT calculations (see the SI for details).…”

Section: Resultsmentioning

confidence: 99%

Investigations on the Novel Antimalarial Ferroquine in Biomimetic Solutions Using Deep UV Resonance Raman Spectroscopy and Density Functional Theory

Domes

Frosch

2023

Anal. Chem.

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Deep ultraviolet (DUV) resonance Raman experiments are performed, investigating the novel, promising antimalarial ferroquine (FQ). Two buffered aqueous solutions with pH values of 5.13 and 7.00 are used, simulating the acidic and neutral conditions inside a parasite’s digestive vacuole and cytosol, respectively. To imitate the different polarities of the membranes and interior, the buffer’s 1,4-dioxane content was increased. These experimental conditions should mimic the transport of the drug inside malaria-infected erythrocytes through parasitophorous membranes. Supporting density functional theory (DFT) calculations on the drug’s micro-speciation were performed, which could be nicely assigned to shifts in the peak positions of resonantly enhanced high-wavenumber Raman signals at λexc = 257 nm. FQ is fully protonated in polar mixtures like the host interior and the parasite’s cytoplasm or digestive vacuole (DV) and is only present as a free base in nonpolar ones, such as the host’s and parasitophorous membranes. Additionally, the limit of detection (LoD) of FQ at vacuolic pH values was determined using DUV excitation wavelengths at 244 and 257 nm. By applying the resonant laser line at λexc = 257 nm, a minimal FQ concentration of 3.1 μM was detected, whereas the pre-resonant excitation wavelength 244 nm provides an LoD of 6.9 μM. These values were all up to one order of magnitude lower than the concentration found for the food vacuole of a parasitized erythrocyte.

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“…The multi-parameters coefficients within Kamlet-Taft equation are ordered in Table 2, the results showed that the positive sign of the (a coefficient) for pKa 1 in water-dioxane blends, which suggests that decrease in the acidity with increasing mole fraction of dioxane cause decrease of the pKa 1 magnitueds. Thus, a has major role for the system [34] compared to basicity of solvent, the rational for this phenomenon may be a significant difference within the preferential solvation effects of the studied indicator. However, negative sign of (s coefficient) indicates that a decrease in the polarity of the media increases the dissociation constants.…”

Section: The Correlation Of Acidity Constants With Kamlet-taft Parame...mentioning

confidence: 99%

Investigations of solvent parameters on acidity dissociation constants of bromocresol purple in water-dioxane media

Saad Hemdan,

Mansour Al Gebali,

Khairallah Ali

2023

JCTM

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The acidity constants (pKa) of bromocresol purple in various water-dioxane mixtures were determined. The proposed approaches allow prediction of pKa values of bromocresol purple in any mixture of water-dioxane. The results were discussed in terms of the solvent characteristic. The pKa values of the investigated indicator were found to be largely dependent on the ratio of dioxane. This result is confirmed by linear correlation between mol fraction of dioxane and acidity constant due to the solvation of bromocresol purple with both water and dioxane molecules in all binary mixtures. The results showed non-linear relationship between pKa values and reciprocal relative permittivity that indicates both the electrostatic and non-electrostatic which affecting on the acidity constant. A linear solvation free energy relationship was used to study the effects of solvent and solute properties on the acidity constants in some dioxane solvent mixtures. The pKa values were correlated with the Kamlet-Taft solvatochromic parameters of mixtures from water with dioxane. It was mainly affected by non-electrostatic solute-solvent interactions. The KAT multi-parameter correlations represent significant improvements with regard to single-or dual-parameter models with highest F-static.

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Complete resolution of the ionization equilibria of 5-deoxypyridoxal in water-dioxane mixtures

Cited by 9 publications

References 18 publications

Resolution of Microscopic Protonation Enthalpies of Polyprotic Molecules by Means of Cluster Expansions

Resolution of Microscopic Protonation Enthalpies of Polyprotic Molecules by Means of Cluster Expansions

Investigations on the Novel Antimalarial Ferroquine in Biomimetic Solutions Using Deep UV Resonance Raman Spectroscopy and Density Functional Theory

Investigations of solvent parameters on acidity dissociation constants of bromocresol purple in water-dioxane media

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