Acidities of strong neutral Brønsted acids in different media

Raamat, Elin; Kaupmees, Karl; Ovsjannikov, Gea; Trummal, Aleksander; Kütt, Agnes; Saame, Jaan; Koppel, Ivar; Kaljurand, Ivari; Lipping, Lauri; Rodima, Toomas; Pihl, Viljar; Koppel, Ilmar A.; Leito, Ivo

doi:10.1002/poc.2946

Cited by 219 publications

(204 citation statements)

References 50 publications

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“…33 32 was used. COSMO BP/TZVP geometry optimizations within RI approximation were carried out first in the conductor limit with Turbomole software package 34 for the studied base and corresponding conjugated acid.…”

Section: Experimental Computational Methodsmentioning

confidence: 99%

Basicities of Strong Bases in Water: A Computational Study

Kaupmees¹,

Trummal²,

Leito³

2014

Croat. Chem. Acta

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Abstract.Aqueous pKa values of strong organic bases -DBU, TBD, MTBD, different phosphazene bases, etc -were computed with CPCM, SMD and COSMO-RS approaches. Explicit solvent molecules were not used. Direct computations and computations with reference pKa values were used. The latter were of two types: (1) reliable experimental aqueous pKa value of a reference base with structure similar to the investigated base or (2) reliable experimental pKa value in acetonitrile of the investigated base itself.The correlations of experimental and computational values demonstrate that direct computations do not yield pKa predictions with useful accuracy: mean unsigned errors (MUE) of several pKa units were observed. Computations with reference bases lead to MUE below 1 pKa unit and are useful for predictions. Recommended aqueous pKa values are proposed for all investigated bases taking into account all available information: experimental pKa values in acetonitrile and water (if available), computational pKa values, common chemical knowledge.

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Section: Experimental Computational Methodsmentioning

confidence: 99%

Basicities of Strong Bases in Water: A Computational Study

Kaupmees¹,

Trummal²,

Leito³

2014

Croat. Chem. Acta

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“…When 4 to 10% molar TfOH is added, this cation chelation is accelerated and a purple coloration of the solution is noticed. On the other hand, one can observe that the addition of small amounts of TfOH does not affect the electrochemical features of the chemosensors (figure not shown); since TfOH is a weak acid in organic solvents (pK a = 0.7 in ACN) [31], the protonated amounts of 1 and 2 should remain very low and the oxidation currents are unaltered. Besides, the addition of an increasing quantity of acid (up to 20%) does not affect the electrochemical behavior of TAPD compounds, nor are the potentials or the currents of the peaks altered.…”

Section: Electrochemistry Of the Chemosensors In Presence Ofmentioning

confidence: 99%

Solvent Effects on the Electrochemical Behavior of TAPD-Based Redox-Responsive Probes for Cadmium(II)

Sahli

Bahri

Tapsoba

et al. 2014

International Journal of Electrochemistry

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Two tetralkylated phenylenediamines (TAPD) 1 and 2 have been prepared by reductive alkylation of para-dimethylaminoaniline with furfural or thiophene 2-carboxaldehyde, respectively. Their chelation ability has been evaluated as electrochemical guest-responsive chemosensors for Cd(II) in acetonitrile (ACN), dimethylformamide (DMF), propylene carbonate (PC), and nitromethane (NM). The voltamperometric studies showed that these compounds are able to bind the Cd(II) cation with strong affinities except in DMF. The redox features of the chemosensors changed drastically when they are bounded to Cd(II) to undergo important anodic potential peak shifts comprised between ca. 500 and ca. 900 mV depending on the solvent. The addition of ∼4-10% molar triflic acid (TfOH) was found to be necessary to achieve rapidly the cation chelation which is slow without the acid. The electrochemical investigations suggested the formation of 1 : 2 stoichiometry complexes [Cd(L) 2 ]2+ . The results are discussed in terms of solvent effects as a competitive electron donating ligand to the cation. The reaction coupling efficiency (RCE) values were determined and were also found to be solvent-dependent.

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“…For the sulfonic group the model compound is triflic acid with pKa = -12 and for the sulfonimide group the model compound is bisperfluoroethyl sulfonimide with pKa < -2. 69 From these values of pKa we conclude that for typical values of pH of ionomer membranes (that is around 0) most of both sulfonic and sulfonimide acidic groups are dissociated. Thus, the charge of the PFSA side chain is −1 and the charge of the PFIA side chain is −2.…”

Section: Molecular Dynamics Modelmentioning

confidence: 99%

Molecular Dynamic Study of Water-Cluster Structure in PFSA and PFIA Ionomers

Atrazhev

Astakhova

Sultanov³

et al. 2017

J. Electrochem. Soc.

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Molecular-dynamics simulations were used to study the structure of water clusters in different perfluorinated ionomers. The ionomers included in this work were Perfluorosulfonic Acid (PFSA) and Perfluoroimide Acid (PFIA). Different shapes and sizes of water domains in PFSA and PFIA were observed. In PFSA, ionomer water domains have spherical-like shape while water domains have complicated branch structure in PFIA ionomer. The mean water-cluster size for PFSA and PFIA ionomers as a function of water content lie on one universal curve, which indicates that the size of water clusters depends primarily on water content and weakly on ionomer chemistry. In PFSA, almost all hydronium ions are located predominantly close to the water cluster/backbone interface for both large and small values of water content; while in PFIA a relatively large fraction of hydronium ions are distributed within the bulk of the water clusters. A similar distribution of acidic groups was observed in both ionomers. In PFSA ionomer, all sulfonic groups are located in the surface water layer at the distance from 3 Å to 6 Å from the backbone. In PFIA ionomer, approximately 60% of sulfonic groups are located in the surface water layer and 40% of sulfonic groups are immersed into the bulk of water cluster. Perfluorinated ion-exchange membranes are widely used in both fuel cells and flow-battery cells. Flow batteries, such as vanadium redox batteries (VRBs), are promising devices for the large-scale Electrical Energy Storage (EES) applications 1 and are receiving increasing interest due to the demand for grid-scale EES solutions and recent improvements in VRB cell performance.2 The ion-exchange membrane is a critical component in these different types of electrochemical flow cells, which conducts the charge-carrier ions (e.g., protons) while preventing the flow of electrons through it. Additionally, in a flow-battery cell, the membrane separates the positive and negative liquid electrolytes containing the active redox-species ions. For example, in a VRB cell, it is desirable to prevent the crossover of vanadium ions through the membrane since the result is a decrease in both the energy efficiency and energy capacity of the VRB system. 2,3 In VRBs, this energy-capacity loss is recoverable, since the vanadium can be simply rebalanced by pumping some of the electrolyte with the excess V to the other electrolyte tank (albeit with an additional energy loss due to self-discharging that results from mixing the two reactants). In flow-battery chemistries with dissimilar active-species ions (e.g., Fe-Cr systems), crossover can also cause contamination of the electrolytes and/or electrodes, which can result in additional adverse effects on the flow-battery system. 1 In any case, the activespecies ions are transported through the membrane in the hydrophilic phase (i.e., the water clusters) of the membrane. Therefore, the study of the water-cluster structure is required to understand and model the transport of different ions in the membrane. One of the ultimate...

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Acidities of strong neutral Brønsted acids in different media

Cited by 219 publications

References 50 publications

Basicities of Strong Bases in Water: A Computational Study

Basicities of Strong Bases in Water: A Computational Study

Solvent Effects on the Electrochemical Behavior of TAPD-Based Redox-Responsive Probes for Cadmium(II)

Molecular Dynamic Study of Water-Cluster Structure in PFSA and PFIA Ionomers

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