Protonation of Pyridine Monocarboxylate‐N‐Oxides – Determination of Thermodynamic, Absorbance and Ion Interaction Parameters

Dumpala, Rama Mohana Rao; Rawat, N.S.; Tomar, B. S.

doi:10.1002/slct.201601322

Cited by 5 publications

(3 citation statements)

References 59 publications

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“…Thus, these reactions are majorly entropy-driven protonations. The ΔH P for the protonation of formates, acetates, and propionates under similar experimental conditions are 1.28, 1.68, and, 1.08 kJ/mol, respectively; 44 the present study also revealed a similar trend of ΔH P2 for the protonation of the carboxylate group of the ligand. Minofar et al studied the hydration of aliphatic dicarboxylate anions of varying chain lengths and found that the hydrophilic interactions of charged species are dominant over hydrophobic interactions of the alkyl chain up to adipate, and these dianions are encapsulated in hydration shells.…”

Section: Protonation Constantssupporting

confidence: 80%

Protonation of Phosphonocarboxylates in Aqueous Medium: An Experimental and Theoretical Investigation

et al. 2022

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Phosphonates and carboxylates are two primitive functional groups omnipresent in nature, and they act as good chelators for metal ion binding. These two functional groups are always associated with dissociable protons in their acidic forms. Thus, their interactions are associated with protonation/deprotonation mechanisms. The present study was aimed at determining the thermodynamic parameters (log K P/pK a, ΔG P, ΔH P, and ΔS P) for the protonation of three aliphatic phosphonocarboxylates, namely, phosphonoformic acid (PFA), phosphonoacetic acid (PAA), and phosphonopropanoic acid (PPA), which differ in their spacer (connecting −CH2 moiety) length. Potentiometric and isothermal titration calorimetric studies were employed to determine the protonation constants (log K P/pK a) and enthalpies (ΔH P) of the three phosphonocarboxylates. All of the acids have three protonation sites ranging in pK a values from 1.8 to 7.4. The enthalpies of protonation are close to ±5 kJ/mol, except for the third protonation, and these protonations are mainly entropy-driven interactions. Density functional theory calculations were carried out to estimate interatomic distances and partial charges on all of the atoms to gain insights into the protonation mechanism at the molecular level. The predicted theoretical estimations followed the experimentally observed protonation trends.

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Section: Protonation Constantssupporting

confidence: 80%

Protonation of Phosphonocarboxylates in Aqueous Medium: An Experimental and Theoretical Investigation

et al. 2022

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“…Upon complexations, extractants with dissociable protons are prone to protonation and deprotonation, and thus, a change in the hydrogen ion concentration (pH) is a good indicator of complexation progress. − In the present study, the sequential progress of complexation is probed by adding a concentrated ligand solution into a fixed concentration of a metal solution and monitoring the pH after each addition of the ligand. Potentiometric data were analyzed by Hyperquad program , to deduce the species present along with stability for complex formation during the course of the reaction.…”

Section: Resultsmentioning

confidence: 99%

Thorium Complexation with Aliphatic and Aromatic Hydroxycarboxylates: A Combined Experimental and Theoretical Study

Kumar,

Dumpala,

Telmore

et al. 2024

ACS Omega

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“…The chemical nature of the participating ligand and the geometry arrived by its coordination on the equatorial plane has phenomenal effects on the intensities and positions of electronic transitions of the uranyl ion in the range of 380–480 nm arising from vibronic perturbed electronic transitions. , The protonation process is an inseparable mechanism while studying the complexation phenomenon, − especially with the protonated/deprotonated ligands; and the protonation thermodynamic data are a prerequisite to obtain the complexation thermodynamics data. The present studies utilized the protonation data from our previous work .…”

Section: Resultsmentioning

confidence: 99%

Chemical and Redox Speciation of Uranyl with Three Environmentally Relevant Bifunctional Chelates: Multi-Technique Approach Combined with Theoretical Estimations

et al. 2022

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Carbon and phosphorous are two primary elements common to the bio-geosphere and are omnipresent in both biotic and abiotic arenas. Phosphonate and carboxylate are considered as building blocks of glyphosate and humic substances and constituents of the cellular wall of bacteria and are the driving functionalities for most of the chemical interactions involving these two elements. Phosphonocarboxylates, a combination of both the functionalities in one moiety, are ideal models to dig deep into for understanding the chemical interactions of the two functional groups with metal ions. Phosphorous and carbon majorly exist as inorganic/organic phosphate and carboxylate, respectively, in the bio-geosphere. Aquatic contamination is a major concern for uranium, and the presence of complexing agents would alter the uranium concentrations in aquifers. Determination of solution thermodynamic parameters, speciation plots, redox patterns, E h −pH diagrams, coordination structures, and molecular-level understanding by density functional theory calculations was carried out to interpret the uranyl (UO 2 2+ ) interaction with three environmentally relevant phosphonocarboxylates, namely, phosphono-formic acid (PFA), phosphono-acetic acid (PAA), and phosphono-propanoic acid (PPA). UO 2 2+ forms 1:1 complexes with the three phosphonocarboxylates in the monoprotonated form, having nearly the same stability, and the complexes [UO 2 (PFAH)], [UO 2 (PAAH)], and [UO 2 (PPAH)] involve chelate formation of five, six, and seven membered rings, respectively, through the participation of an oxygen each from the carboxylate and phosphonate, strengthened by an intra-molecular hydrogen bonding through the proton of the phosphonate moiety with uranyl oxygen. The complex formations are favored both enthalpically and entropically, with the latter being more contributive to the overall free energy of formation. The redox speciation showed an aqueous soluble complex formation over a wide pH range of 1−8. Electrospray ionization mass spectrometry and extended X-ray absorption fine structure established the coordination modes, which are further corroborated by density functional calculations. The knowledge gained from the present studies provide potential inputs in framing the cleanup, sequestering, microbial, and bio-remediation strategies for uranyl from aquatic environments.

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Protonation of Pyridine Monocarboxylate‐N‐Oxides – Determination of Thermodynamic, Absorbance and Ion Interaction Parameters

Cited by 5 publications

References 59 publications

Protonation of Phosphonocarboxylates in Aqueous Medium: An Experimental and Theoretical Investigation

Protonation of Phosphonocarboxylates in Aqueous Medium: An Experimental and Theoretical Investigation

Thorium Complexation with Aliphatic and Aromatic Hydroxycarboxylates: A Combined Experimental and Theoretical Study

Chemical and Redox Speciation of Uranyl with Three Environmentally Relevant Bifunctional Chelates: Multi-Technique Approach Combined with Theoretical Estimations

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