Determination of ionization constants of monobasic acids in ethanol-water solvents by direct potentiometry

Frohliger, John O.; Gartska, R. A.; Irwin, Hildred W.; Stewward, O. W.

doi:10.1021/ac60266a018

Cited by 11 publications

(5 citation statements)

References 5 publications

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“…No data of such a kind were available for MeCN-water mixtures. However, the assumption that their pK values grow up on increasing the MeCN content can be supported by the evidence that the pK values of such substances as phenol, acetic, propionic and benzoic acids (somewhat mimicking the protein α-COOH, Glu and Asp side chains) increase by approximately 2 pK units on addition of ethanol up to 70% in water solutions and by 3-3.5 pK units on addition of acetone up to the same high concentration [43], [44]. Therefore, an increase in pK values of the protein titratable groups in MeCN-water mixtures can also be expected since MeCN does not differ much from acetone and ethanol by physico-chemical properties.…”

Section: A2 Enthalpy Of Transitionmentioning

confidence: 99%

On the stabilizing action of protein denaturants: acetonitrile effect on stability of lysozyme in aqueous solutions

Kovrigin

Potekhin

2000

Biophysical Chemistry

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Stability of hen lysozyme in the presence of acetonitrile (MeCN) at different pH values of the medium was studied by scanning microcalorimetry with a special emphasis on determination of reliable values of the denaturational heat capacity change. It was found that the temperature of denaturation decreases on addition of MeCN. However, the free energy extrapolation showed that below room temperature the thermodynamic stability increases at low concentrations of MeCN in spite of the general destabilizing effect at higher concentrations and temperatures. Charge-induced contribution to this stabilization was shown to be negligible (no pH-dependence was found); therefore, the most probable cause for the phenomenon is an increase of hydrophobic interactions at low temperatures in aqueous solutions containing small amounts of the organic additive. The difference in preferential solvation of native and denatured states of lysozyme was calculated from the stabilization free energy data. It was found that the change in preferential solvation strongly depends on the temperature in the water-rich region. At the higher MeCN content this dependence decreases until, at 0.06 mole fractions of MeCN, the difference in the preferential solvation between native and denatured lysozyme becomes independent of the temperature over a range of 60 K. The importance of taking into account non-ideality of a mixed solution, when analyzing preferential solvation phenomena was emphasized.

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Section: A2 Enthalpy Of Transitionmentioning

confidence: 99%

On the stabilizing action of protein denaturants: acetonitrile effect on stability of lysozyme in aqueous solutions

Kovrigin

Potekhin

2000

Biophysical Chemistry

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“…Potentiometry can be used to determine the pka in non-aqueous solvents. 43 Finally, it should be noted that although some of the dispersants in this study prevented aggregation more effectively than others, all of the dispersions showed noticeable settling after 1 week. The observed lack of stability is likely due to the relatively large particle sizes of the NiO in conjunction with the density mismatch between NiO (6.67 g/cm 3 ) and 2-butanol (0.8063 g/cm 3 ), and the relatively low viscosity of 2-butanol (3.10 mPas at 25°C).…”

Section: Discussionmentioning

confidence: 66%

“…Furthermore, if the pKa of a given acid type dispersant is measured for the formulating solvent of interest, then the strength of the dispersant bond to the NiO surface may be predictable. Potentiometry can be used to determine the pka in non‐aqueous solvents …”

Section: Discussionmentioning

confidence: 99%

Mechanisms of Fatty Acid and Triglyceride Dispersant Bonding in Non‐Aqueous Dispersions of NiO

2013

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Infrared spectroscopy was used to identify the mechanism of fatty acid and triglyceride dispersant bonding to NiO in 2‐butanol for a series of triglyceride and straight chain fatty acid dispersants with systematically varied chain lengths and degrees of unsaturation. The extent of NiO deflocculation was measured using laser diffraction particle size analysis. The relative stabilities of the fatty acid/NiO dispersions were assessed through settling tests. Diffuse reflectance infrared spectroscopy indicates that the straight chain fatty acids chemisorb to NiO as alkoxides with most of the adsorbed moieties in an η2 configuration. A small fraction of the adsorbed straight chain fatty acids are either chemisorbed through the hydroxyl oxygen in an η1 configuration or physisorbed as dimers. Glycerol trioleate and Menhaden fish oil both exhibit some chemisorption through the carbonyl oxygen. Despite similarities in adsorption mechanism, the dispersants differ in their abilities to break up NiO aggregates and to prevent re‐aggregation. Dispersant characteristics favoring stability of the NiO/2‐butanol dispersion are longer carbon chain length and higher degree of unsaturation. The triglyceride structure provides a weak improvement in stability. These results are discussed in the context of recent work developing non‐aqueous inks for inkjet printing of solid oxide fuel cells.

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“…As before [8], we calculated log 10 P for transfer from water to water-ethanol mixtures for the neutral species from known descriptors and Eqs. 2-11. Values of pK a for monocarboxylic acids in water-ethanol mixtures have been determined by Grunwald and Berkowitz [15], Spivey and Shedlovsky [16], Frohlinger et al [17], Dash and Pattanaik [18], Azab et al [19], and Thuaire [20]. For acetic acid, they are all in agreement [15][16][17][18][19][20] and we have used them to obtain values at rounded-off vol-% ethanol.…”

Section: Resultsmentioning

confidence: 88%

“…2-11. Values of pK a for monocarboxylic acids in water-ethanol mixtures have been determined by Grunwald and Berkowitz [15], Spivey and Shedlovsky [16], Frohlinger et al [17], Dash and Pattanaik [18], Azab et al [19], and Thuaire [20]. For acetic acid, they are all in agreement [15][16][17][18][19][20] and we have used them to obtain values at rounded-off vol-% ethanol. There are less data for formic acid [15], propanoic acid [15,18] and butanoic acid [15,18].…”

Section: Resultsmentioning

confidence: 88%

Equations for the Partition of Neutral Molecules, Ions and Ionic Species from Water to Water–Ethanol Mixtures

Abraham

Acree

2012

J Solution Chem

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Equations set up for the transfer of neutral solutes from water to water-ethanol mixtures can also be used to correlate the transfer of ions and ionic species, as log 10 P , where P is the partition coefficient. Only two additional terms are required in the equations, one for anions and one for cations. The extended equations can fit log 10 P values for anions and cations with a standard deviation of about 0.2 to 0.3 log units for transfer of 41 anions and cations from water to various water-ethanol mixtures from 10 % ethanol to 100 % ethanol by volume. The log 10 P values for carboxylate anions and protonated amine cations as obtained from the variation of pK a with solvent are quite compatible with log 10 P values for simple anions and cations.

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Determination of ionization constants of monobasic acids in ethanol-water solvents by direct potentiometry

Cited by 11 publications

References 5 publications

On the stabilizing action of protein denaturants: acetonitrile effect on stability of lysozyme in aqueous solutions

On the stabilizing action of protein denaturants: acetonitrile effect on stability of lysozyme in aqueous solutions

Mechanisms of Fatty Acid and Triglyceride Dispersant Bonding in Non‐Aqueous Dispersions of NiO

Equations for the Partition of Neutral Molecules, Ions and Ionic Species from Water to Water–Ethanol Mixtures

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