Statistical methods in determining dissociation constants and chemical shifts for N-acylonium ions and ion pairs

1988 ◽  
Vol 23 (4) ◽  
pp. 467-470
Author(s):  
L. M. Kapkan ◽  
S. A. Lapshin ◽  
Yu. I. Smirnov
Keyword(s):  
Statistical Methods ◽  
Dissociation Constants ◽  
Chemical Shifts ◽  
Ion Pairs

Solution Properties of Tetraalkylammonium Halide and Alkali-Metal Halide Ion Pairs. The Relationship Between Dissociation Constants and Solubility Products

1987 ◽  
Vol 40 (7) ◽  
pp. 1201 ◽  
Author(s):  
W Mizerski ◽  
MK Kalinowski
Keyword(s):  
Alkali Metal ◽  
Solubility Product ◽  
Dissociation Constants ◽  
Ion Pairs ◽  
Empirical Relation ◽  
Alkali Metal Halide ◽  
Alkali Metal Cations ◽  
Solubility Products ◽  
The Relationship ◽  
Dissociation Constant Kd

An empirical relation describing the effect of solvent on the dissociation constant ( Kd ) of ion pairs is described. An equation of the form pKd = apKso + bD-1 + c ( Kso and D stand for the solubility product of a given salt and for the electric permittivity of a solvent, respectively) has been tested with 13 sets of experimental data for salts containing tetraalkylammonium and alkali-metal cations. A successful correlation was obtained in 100% of the cases considered.

scholarly journals Protolysis and Complex Formation of Organophosphorus Compounds—Characterization by NMR-Controlled Titrations

Molecules ◽  
2019 ◽  
Vol 24 (18) ◽  
pp. 3238 ◽  
Author(s):  
Hägele
Keyword(s):  
Dissociation Constants ◽  
Organophosphorus Compounds ◽  
Chemical Shifts ◽  
2D Nmr ◽  
Coupling Constants ◽  
Phosphonic Acids ◽  
Specific Chemical ◽  
Hyphenated Technique ◽  
Aminophosphonic Acids ◽  
2D Nmr Spectra

Phosphonic acids, aminophosphonic acids, and phosphonocarboxylic acids are characterized by an advanced hyphenated technique, combining potentiometric titration with NMR spectroscopy. Automated measurements involving 13C, 19F and 31P nuclei lead to “pseudo 2D NMR” spectra, where chemical shifts or coupling constants are correlated with analytical parameters. Dissociation constants, stability constants, dynamic and specific chemical shifts are determined. Macroscopic and microscopic dissociation equilibria are discussed.

Ionic association in aqueous solutions of bivalent sulphates

1969 ◽  
Vol 313 (1512) ◽  
pp. 131-147 ◽  
Keyword(s):  
Aqueous Solution ◽  
Osmotic Coefficient ◽  
Dissociation Constants ◽  
Divalent Cations ◽  
Ion Pairs ◽  
Osmotic Coefficients ◽  
Close Approach ◽  
Complete Analysis ◽  
Hydration Water ◽  
Similar Magnitude

Osmotic coefficient data for the sulphates of Mg, Ca, Zn, Ni and Cu in aqueous solution have been analysed to obtain the dissociation constants (d.c.) of ion pairs, triplets and quadruplets, as well as information on their state of hydration. The d.c.’s of the sulphate ion pairs, though of similar magnitude, show distinct individualities, and the trend is similar to that of the d.c.’s calculated for the nitrates of di-valent ions, though the d.c.’s of the latter are about 200 times larger. The d.c.’s of the ion triplets show no correlations, but their absolute values are similar to those calculated from the theory of Fuoss & Kraus (1933, 1935) based on electrostatic considerations. The hydration parameters of the associated sulphates (both pairs and triplets), as characterized in the linear (statistical) terms of the osmotic coefficients, are only slightly smaller than those of the fully dissociated electrolytes, indicating that there is only little loss of hydration water in the process of association, in spite of the heavy hydration of the divalent cations and the relatively close approach of the sulphate ion. The complete analysis of the osmotic coefficient curves makes it possible to calculate the absolute values of the activity coefficients of the divalent sulphates (previously not known to any accuracy).

Electrical conductivities of quaternary ammonium salts in acetone.: Part III. Ion-pair formation

1968 ◽  
Vol 46 (12) ◽  
pp. 2005-2011 ◽  
Author(s):  
W. A. Adams ◽  
K. J. Laidler
Keyword(s):  
Dissociation Constants ◽  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Quaternary Ammonium Salts ◽  
Acetone Solution ◽  
Ammonium Salts ◽  
Electrical Conductivities ◽  
Tetraethylammonium Iodide ◽  
Kbar Pressure

The ion-pair dissociation constants determined from a Shedlovsky analysis of conductivity (see Part I) were used to calculate the enthalpy, the internal energy at constant volume, the entropy, and the volume of dissociation of tetramethylammonium iodide, tetraethylammonium iodide, and tetra-n-propylammonium iodide ion pairs in acetone solution. The sign and magnitude of these parameters over the range of conditions investigated, temperature 25 to 55 °C and atmospheric to 1.1 kbar pressure, indicated that the free ions in acetone solution are extensively solvated and that, depending on the conditions, solvent-shared or solvent-separated ion pairs are formed.

Ion Association Effects on Nuclear Magnetic Resonance Parameters of Aromatic Ions. II. The Anions of Carbazole and 4,5-Methylenephenanthrene

1971 ◽  
Vol 49 (9) ◽  
pp. 1377-1383 ◽  
Author(s):  
Richard H. Cox
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Alkali Metal ◽  
Chemical Shifts ◽  
Ion Pairs ◽  
Ion Association ◽  
Coupling Constants ◽  
Alkali Metal Cations ◽  
Aromatic Ions ◽  
Magnetic Resonance Parameters

The 1H n.m.r. spectra of carbazole nitranion, 4,5-methylene- and 9,10-dihydro-4,5-methylene-phenanthrene carbanions with various alkali metal cations have been analyzed in terms of chemical shifts and coupling constants. Chemical shifts of the anions depend upon cation and solvent and are related to the type of ion pairs present. The 7Li n.m.r. data indicate that Li is associated with the nitrogen of carbazole nitranion whereas with the 4,5-methylenephenanthrene carbanions, Li appears to be located in the π-cloud of the anions and associated equally with all carbons in the anion. The results are discussed in terms of the types of ion pairs present and the association of cation with anion.

Asymmetric protonation of glutamate residues drives a preferred transport pathway in EmrE

2021 ◽  
Vol 118 (41) ◽  
pp. e2110790118
Author(s):  
Jianping Li ◽  
Ampon Sae Her ◽  
Nathaniel J. Traaseth
Keyword(s):  
Lipid Bilayers ◽  
Efflux Pump ◽  
Dissociation Constants ◽  
Chemical Shifts ◽  
Acid Dissociation ◽  
Coupled Transport ◽  
Wild Type ◽  
Multidrug Efflux Pump ◽  
Transport Pathway ◽  
Small Multidrug Resistance

EmrE is an Escherichia coli multidrug efflux pump and member of the small multidrug resistance (SMR) family that transports drugs as a homodimer by harnessing energy from the proton motive force. SMR family transporters contain a conserved glutamate residue in transmembrane 1 (Glu14 in EmrE) that is required for binding protons and drugs. Yet the mechanism underlying proton-coupled transport by the two glutamate residues in the dimer remains unresolved. Here, we used NMR spectroscopy to determine acid dissociation constants (pKa) for wild-type EmrE and heterodimers containing one or two Glu14 residues in the dimer. For wild-type EmrE, we measured chemical shifts of the carboxyl side chain of Glu14 using solid-state NMR in lipid bilayers and obtained unambiguous evidence on the existence of asymmetric protonation states. Subsequent measurements of pKa values for heterodimers with a single Glu14 residue showed no significant differences from heterodimers with two Glu14 residues, supporting a model where the two Glu14 residues have independent pKa values and are not electrostatically coupled. These insights support a transport pathway with well-defined protonation states in each monomer of the dimer, including a preferred cytoplasmic-facing state where Glu14 is deprotonated in monomer A and protonated in monomer B under pH conditions in the cytoplasm of E. coli. Our findings also lead to a model, hop-free exchange, which proposes how exchangers with conformation-dependent pKa values reduce proton leakage. This model is relevant to the SMR family and transporters comprised of inverted repeat domains.

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