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.

THE IONIZATION CONSTANTS OF p-NITROPHENYLACETIC AND PHENYLMALONIC ACIDS

1933 ◽  
Vol 8 (5) ◽  
pp. 447-449 ◽  
Author(s):  
Steward Basterfield ◽  
James W. Tomecko
Keyword(s):  
Benzoic Acid ◽  
Nitro Group ◽  
Malonic Acid ◽  
Phenylacetic Acid ◽  
Ionization Constants ◽  
Side Chain ◽  
Cooh Group ◽  
Conductivity Data ◽  
Nitrobenzoic Acid ◽  
Phenylmalonic Acid

The ionization constants of p-nitrophenylacetic and phenylmalonic acids have been determined from conductivity data. The value of K for p-nitrophenylacetic acid at 25 °C. is 1.04 × 10−4, about twice that of phenylacetic acid. The nitro group in the nucleus has not as powerful an effect on the ionization when the COOH group is in the side chain as it has when both nitro group and COOH are in the nucleus. K for p-nitrobenzoic acid is six times as great as K for benzoic acid. K for phenylmalonic acid is 2. 77 × 10−3 as compared with 1.6 × 10−3 for malonic acid.

Aggregation and adsorption behaviors of carboxymethylated lignin (CML) in aqueous solution

Holzforschung ◽  
2013 ◽  
Vol 67 (4) ◽  
pp. 379-385 ◽  
Author(s):  
Linhuo Gan ◽  
Mingsong Zhou ◽  
Dongjie Yang ◽  
Xueqing Qiu
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Gold Surface ◽  
Point Of View ◽  
Water Soluble ◽  
Critical Aggregation Concentration ◽  
Cooh Group ◽  
Adsorption Behaviors ◽  
Group Content ◽  
Soluble Lignin

Abstract Carboxymethylated lignin (CML) as a water-soluble lignin derivative is a multipurpose adsorbent and dispersant. In this article, the aggregation and adsorption behaviors of CML have been investigated in aqueous solution using fluorescence spectroscopy, dynamic light scattering, and a quartz crystal microbalance combined with dissipation monitoring techniques. It was found that CML forms aggregates when its concentration exceeds the critical aggregation concentration (CAC). The CAC of CML1 with a carboxylic (COOH) group content of 2.8 mmol g-1 was 0.022 g l-1, and that of CML2 with a COOH group content of 2.0 mmol g-1 was 0.026 g l-1. The adsorption behavior of CML on the gold surface was strongly dependent on the pH and ionic strength of the solution. At low pH and ionic strength, more CMLs were adsorbed at the gold/water interface, and the layers were rigid. The results could be used not only from the theoretical but also from the application point of view.

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

scholarly journals The stability and aggregation properties of human liver acid β-d-galactosidase

1981 ◽  
Vol 193 (3) ◽  
pp. 773-779 ◽  
Author(s):  
C M Heyworth ◽  
E F Neumann ◽  
C H Wynn
Keyword(s):  
Ionic Strength ◽  
Molecular Form ◽  
Active Form ◽  
Gel Filtration ◽  
British Library ◽  
Fluorescence Excitation ◽  
Dimeric Form ◽  
The Stability ◽  
Low Ionic Strength ◽  
Beta Galactosidase

1. A method is described for following continuously the action of beta-galactosidase on 4-methylumbelliferyl beta-D-galactoside at pH 4.5, in which 4-methylumbelliferone production is measured at fluorescence excitation and emission wavelengths of 324 and 444nm respectively. 2. Initial-rate studies show that the presence of salt activates beta-galactosidase up to 100 mM, but is inhibitory above that concentration. The enzyme is very unstable at 37 degrees C and low ionic strength, but stability increases with ionic strength. 3. The stability of the enzyme at 37 degrees C decreases markedly with rising pH in the range 5.9–8.0. 4. Gel-filtration patterns demonstrate that there is a marked tendency to polymerization with increasing ionic strength. The gel-filtration pattern shows decreasing amounts of dimer with increasing pH. 5. The correlation between activity, stability and molecular form of beta-galactosidase is discussed. It is suggested that the dimeric form of the enzyme is the most stable and active form. The implications of this finding for the assay of beta-galactosidase under physiological conditions for prenatal diagnosis are discussed. 6. Evidence for the possible occurrence of a 36 000-mol.wt. from of beta-galactosidase is presented. 7. A computer program for the calculation of initial rates has been deposited as Supplementary Publication SUP 50114 (4 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1981) 193, 5.

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 Development and validation of methods of quantitative determination of biologically active compound n-(2-[4-oxo-3(4h)-quinazolinyl]propionyl)guanidine

2020 ◽  
Vol 19 (5-6) ◽  
pp. 122-127
Author(s):  
Evgenia V. Kompantseva ◽  
Daria N. Lutsenko ◽  
Alexander A. Glushko
Keyword(s):  
Quantitative Determination ◽  
Active Compound ◽  
Molecular Form ◽  
Biologically Active ◽  
Ionization Constants ◽  
Error Limit ◽  
Analytical Wavelength ◽  
Biologically Active Compound ◽  
Development And Validation

This paper presents the results of the selection and justification of the conditions for determination of a new biologically active compound (BAC) VMA-13-15, which is N-(2-[4-oxo-3(4H)-quinazolinyl]propionyl)guanidine bymeans of the spectrophotometry. By using the calculated values of BAC ionization constants, it was proposed to use purified water as a solvent. The maximum light absorption at 266 nm was chosen as the analytical wavelength. This was justified by the fact that in aqueous solutions 99% BAC are in the molecular form, which allows to determine it with the error limit of 1.29%, and with the least amount of dilutions. The study showed that the proposed method is specific and linear in the analytical concentration of 0.0010.004%, as well as it is precise and correct, which confirms the possibility of its use for quantitative determination.

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