Ionic equilibriums in mixed solvents. VI. Dissociation constants of aliphatic diamines in water-methanol solutions

1971 ◽  
Vol 75 (1) ◽  
pp. 90-92 ◽  
Author(s):  
Hitoshi Ohtaki ◽  
Nobu Tanaka
Keyword(s):  
Dissociation Constants ◽  
Mixed Solvents ◽  
Methanol Solutions ◽  
Aliphatic Diamines

Dissociation of Hydroxamic Acids: Solvent Effects

1993 ◽  
Vol 58 (5) ◽  
pp. 1109-1121 ◽  
Author(s):  
Otto Exner ◽  
Martin Hradil ◽  
Jiří Mollin
Keyword(s):  
Ionic Strength ◽  
Solvent Effects ◽  
Dissociation Constants ◽  
Mixed Solvents ◽  
Hydroxamic Acids ◽  
Polar Solvents ◽  
Benzohydroxamic Acid ◽  
Methyl Cellosolve ◽  
Methyl Derivatives

The dissociation constants of benzohydroxamic, 4-chlorobenzohydroxamic, and 4-nitrobenzohydroxamic acids, and their N-methyl and O-methyl derivatives, were measured spectrophotometrically or potentiometrically in mixtures of 2-propanol and water. The results were extrapolated to zero ionic strength. The ratio of dissociation constants of the N-methyl and O-methyl derivatives can be taken to represent - with some approximation - the ratio of NH and OH acidities of the parent acid. This ratio increases with substitution by electron-attracting substituents, and decreases with solvent permittivity: some irregularities might be attributable to the effects of mixed solvents, It follows that 4-nitrobenzohydroxamic acid behaves essentially as N-acid in all solvents, 4-chlorobenzohydroxamic acid only in 90% 2-propanol or 80% methyl cellosolve. In benzohydroxamic acid the NH and OH acidities are comparable, the latter prevails slightly in water, the former in less polar solvents. Some apparent discrepancies in the literature can be explained in the same terms, only a few results have not yet been explained.

Solvent effect on the dissociation of p-nitroanilinium ion in glycerol–water media at 25 °C

1984 ◽  
Vol 62 (11) ◽  
pp. 2245-2248
Author(s):  
Amrita Lal De ◽  
Tapas Kumar De
Keyword(s):  
Solvent Effect ◽  
Dissociation Constants ◽  
Mixed Solvents ◽  
Individual Species ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Monohydric Alcohol ◽  
Glycerol Water ◽  
Alcohol Water ◽  
The Individual

Thermodynamic dissociation constants (sK) of p-nitroanilinium ion (BH+) have been determined at 25 °C in aqueous mixtures of 10, 30, 50, 70, and 90 wt.% of glycerol (GL) by spectrophotometric measurements. Standard free energies, [Formula: see text], of p-nitroaniline (B) from water to mixed solvents have been evaluated from the measurement of solubilities at 25 °C. p(sK) values decrease with increase in mol% of GL and pass through a minimum and then increase very slowly. The solvent effect on the dissociation, δ(ΔG0) = 2.303RT [p(sK)N – p(wK)N] has been discussed in terms of the standard free energies of transfer [Formula: see text] from water to aqueous mixtures of GL of the uncharged base (B), the hydrochloride of the base (BHCl), hydrochloric acid (HCl), and also in terms of the individual species involved in the dissociation process. The solvent effect in trihydric alcohol – water (GL + H2O) system has been compared with those in dihydric alcohol – water (ethylene glycol + water) and monohydric alcohol – water (ethanol + water) systems available from literature. The much less solvent effect in GL + H2O has been primarily attributed to the contrasting nature of interaction of H+ and of partially charged H atoms of—NH3+ group in BH+ compared to those in other two solvent systems.

Comparative Study of CO2 Absorption in Aqueous Mixtures of Methyldiethanolamine (MDEA) and Methanol, Focusing on the Temperature and Concentration Influence over the Absorption Rate

2014 ◽  
Vol 353 ◽  
pp. 193-198
Author(s):  
F.J. Tamajón ◽  
Estrella Álvarez ◽  
F. Cerdeira ◽  
M.E. Vázquez
Keyword(s):  
Absorption Rate ◽  
Mixed Solvents ◽  
Secondary Amines ◽  
Aqueous Mixtures ◽  
Gas Streams ◽  
Process Gas ◽  
Methanol Solutions ◽  
Cell Reactor ◽  
Concentration Changes ◽  
Stirred Cell

The use of tertiary methyldiethanolamine (MDEA) as an absorbent for the CO2 removal from process gas streams has increased due to its advantages over primary and secondary amines. Methanol is also widely used as an organic physical solvent for the CO2 capture. Mixed solvents are expected to have a higher capacity for the acid gases than the solvent alone. The chemical absorption rate of CO2 was measured in mixtures of MDEA (weight 5%, 15% and 30%) and water-methanol solutions at different % weight relations by using a stirred-cell reactor with plane gas-liquid interface. Experiments provided data measured at a range from 283.15 K to 313.15 K operation temperatures. Results show how the solubility of CO2 varies in all systems involved focusing on temperature and concentration changes. The solubility of CO2 in the aqueous mixed MDEA with methanol as a solvent becomes significantly greater than in the aqueous amine alone.

Solvolysis rates in aqueous–organic mixed solvents. IX. Solvolysis of dichloroacetate ion in water–methanol solutions

1981 ◽  
Vol 59 (8) ◽  
pp. 1208-1211 ◽  
Author(s):  
El-Hussieny M. Diefallah ◽  
Mohamed A. Ashy ◽  
Ahmed O. Baghlaf
Keyword(s):  
Mole Fraction ◽  
Reaction Rate ◽  
Mixed Solvents ◽  
Activation Parameters ◽  
Solvent Structure ◽  
Temperature Range ◽  
Methanol Solutions ◽  
Aqueous Organic Mixed Solvents ◽  
Kinetics Of ◽  
Influence Of Solvent

The kinetics of the alkaline solvolysis of dichloroacetate ion in water–methanol solutions have been studied in the temperature range of 50.0 to 65.0 °C and the influence of solvent variation on reaction rate has been examined in terms of changes in the activation parameters. The activation parameters ΔH≠ and ΔS≠ for the solvolysis reaction showed a minimum at about 0.8 water mole fraction. The significance of the results was discussed in view of the electrostatic theory and the changing of solvent structure.

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