The ionization constants of α-alanine in NaCl at 25°. Effect of the ionic strength based on three models

Talanta ◽  
1995 ◽  
Vol 42 (6) ◽  
pp. 797-801 ◽  
Author(s):  
S. Fiol ◽  
I. Brandariz ◽  
M.Sastre de Vicente
Keyword(s):  
Ionic Strength ◽  
Ionization Constants ◽  
Strength Based

Quantitative aspects of base-catalyzed Michael addition: Mechanistic study of structural and medium effects on rate

1969 ◽  
Vol 47 (11) ◽  
pp. 1965-1979 ◽  
Author(s):  
John A. Markisz ◽  
Joseph D. Gettler
Keyword(s):  
Experimental Data ◽  
Ionic Strength ◽  
Ionization Constants ◽  
Mechanistic Study ◽  
Basic Solution ◽  
Ionic Charge ◽  
Quantitative Correlation ◽  
System A ◽  
Kinetics Of ◽  
Good Agreement

The quantitative kinetics of the reactions of acrylonitrile and methyl vinyl ketone with ethyl acetoacetate and 2,4-pentanedione, and those of acrylonitrile with ethanol and methanol in basic solution were studied as functions of base concentration, temperature, ionic strength, and solvent composition. An expression is obtained which relates the observed rates to the basicity of the solution for the 2,4-pentanedione reactions by the amount of anion in solution. For the other systems, reasonable values of ionization constants obtained empirically, similarly correlate observed rates with the concentration of base in the system. A quantitative correlation with activity coefficients as expressed by the expanded form of the Debye–Hückel equation gave good agreement for most of the experimental data with ionic strength. A derivation for the particular type of system employed indicated that the activity coefficient for the double-bonded compounds appears to have to be treated as an ion with partial ionic charge. On the basis of experimental data reported, the mechanism proposed involves, (i) anion attack on a polarized double bond, (ii) formation of a cyclic intermediate, severely restricted because of π orbital overlap, and (iii) protonation of this intermediate to form product.

Determination of macroscopic thermodynamic ionization constants under conditions of variable ionic strength by an optimization algorithm

1990 ◽  
Vol 14 (2) ◽  
pp. 165-168 ◽  
Author(s):  
María N. Moreno ◽  
José Luis González ◽  
M.Angeles del Arco ◽  
Julio Casado
Keyword(s):  
Ionic Strength ◽  
Optimization Algorithm ◽  
Ionization Constants

scholarly journals Protolytic Equilibria in Organized Solutions: Ionization and Tautomerism of Fluorescein Dyes and Related Indicators in Cetyltrimethylammonium Chloride Micellar Solutions at High Ionic Strength of the Bulk Phase

Liquids ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 1-24
Author(s):  
Nikolay O. Mchedlov-Petrossyan ◽  
Natalya A. Vodolazkaya
Keyword(s):  
Ionic Strength ◽  
Molecular Form ◽  
Tautomeric Equilibrium ◽  
Bulk Phase ◽  
Ionization Constants ◽  
Cooh Group ◽  
Micellar Solutions ◽  
Cetyltrimethylammonium Chloride ◽  
Ionic Equilibrium ◽  
Nitro Derivatives

Ionic equilibrium of 22 hydroxyxanthenes, including halogen and nitro derivatives of fluorescein, and their thio- and aza analogues, were studied spectrophotometrically in micellar solutions of cetyltrimethylammonium chloride at ionic strength of the bulk phase 4.0 M KCl. This micellar pseudophase is characterized by the electrostatic surface potential of +(15–16) mV and the ETN value of 0.623. In the case of dyes bearing the COOH group, colorless lactone is the predominant tautomer of the molecular form H2R. A new classification of fluoresceins is developed. The dyes were divided into four groups based on the nature of tautomerism of the anions. In the case of the fluorescein type, the monoanions HR− exist predominantly as “carboxylate” tautomers, with ionized carboxylic and non–ionized hydroxylic group. For the dyes of the eosin type, the situation is opposite, while for the intervening type of compounds, the concentrations of the two tautomers are comparable. Dyes capable of forming lactone anions HR− were classified as the fourth type. For some of them, even the dianion R2− exists as a lactone. The relationship between the stepwise ionization constants, Ka1/Ka2, varies from 1.3 to 1.07 × 105 and is determined by the state of tautomeric equilibrium of molecules and ions.

EFFECT OF CHANGING pH UPON THE RATE AND MECHANISM OF DECARBOXYLATION OF SUBSTITUTED ANTHRANILIC ACIDS

1965 ◽  
Vol 43 (11) ◽  
pp. 3080-3094 ◽  
Author(s):  
G. E. Dunn ◽  
P. Leggate ◽  
I. E. Scheffler
Keyword(s):  
Ionic Strength ◽  
Aromatic Ring ◽  
Maximum Rate ◽  
The Other ◽  
Constant Ionic Strength ◽  
Ionization Constants ◽  
Anthranilic Acids ◽  
Isoelectric Ph

The ionization constants of 4-methoxyanthranilic acid have been determined spectrophotometrically in water at 60 °C and ionic strength 0.10. The variation in rate of decarboxylation with varying pH at constant ionic strength has been measured at 90 °C with 4-methylanthranilic acid and at 60 °C with 4-methoxyanthranilic acid. With each acid the maximum rate occurs at a pH about 2 units less than the isoelectric pH. To account for these results it is necessary to postulate an equilibrium between at least two intermediates formed by protonation of the 1-position of the aromatic ring. One of these must be formed from the anion and the other(s) by protonation of neutral acid and (or) zwitterion.

The ionization constants of phenolic groups in hydroxynaphthalenesulphonic acids

1969 ◽  
Vol 22 (9) ◽  
pp. 1883 ◽  
Author(s):  
Gemert JT van
Keyword(s):  
Ionic Strength ◽  
Hydrogen Atom ◽  
Substituent Effects ◽  
Acid Strength ◽  
Hydroxyl Group ◽  
Ionization Constants ◽  
Secondary Resonance ◽  
Pka Values ◽  
Resonance Effects ◽  
Acid Salts

Ionization constants of the hydroxyl group have been determined for a series of hydroxynaphthalenesulphonic acid salts. Thermodynamic pKa values have been determined for one mono- and one di-sulphonate. The effect of ionic strength is twice as great for the sulphonates as for naphthols. A large difference in acid strength between 1- hydroxynaphthalene-2-sulphonate and 2-hydroxynaphthalene-1-sulphonate has been explained in terms of interaction with the peri-hydrogen atom in the latter. Dewar and Grisdale's expression for substituent effects has been applied to the hydroxynaphthalenesulphonates with nonadjacent substituents. It is concluded that the limitations of the FM treatment are most severe with strongly dipolar substituents and with reaction sites such as -OH and -NH, capable of inducing secondary resonance effects.

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