SOME MEASUREMENTS ON THE IRON (111)–THIOCYANATE SYSTEM IN AQUEOUS SOLUTION

1955 ◽  
Vol 33 (10) ◽  
pp. 1572-1590 ◽  
Author(s):  
M. W. Lister ◽  
D. E. Rivington
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Equilibrium Constant ◽  
Equilibrium Constants ◽  
Spectrophotometric Study ◽  
Concentrated Solutions ◽  
Extinction Coefficients ◽  
Ferric Thiocyanate ◽  
Different Temperatures

A spectrophotometric study of the ferric thiocyanate system is reported. The temperature and ionic strength of the solutions were carefully controlled, and suitable precautions were taken against fading. From the data, values of the equilibrium constant for the formation of FeSCN++ from simple ions, and of the extinction coefficients of FeSCN++ were obtained for different temperatures and ionic strengths, with results that differed somewhat from earlier values. The effect of varying acidity was also investigated. From more concentrated solutions, values for the equilibrium constants for the formation of Fe(SCN)2+ and Fe(SCN)3 were obtained; it was not necessary to postulate higher complexes.

SOME FERRIC HALIDE COMPLEXES, AND TERNARY COMPLEXES WITH THIOCYANATE IONS

1955 ◽  
Vol 33 (10) ◽  
pp. 1603-1613 ◽  
Author(s):  
M. W. Lister ◽  
D. E. Rivington
Keyword(s):  
Ionic Strength ◽  
Constant Temperature ◽  
Ferric Chloride ◽  
Equilibrium Constants ◽  
Spectrophotometric Study ◽  
Ternary Complexes ◽  
Extinction Coefficients ◽  
Halide Complexes ◽  
High Chloride ◽  
Chloride Concentrations

A spectrophotometric study of solutions containing ferric and bromide ions; ferric, bromide, and thiocyanate ions; and ferric, chloride, and thiocyanate ions is reported. The measurements were made at constant temperature and ionic strength. The data were interpreted with the help of the results from the first paper of this series. The data show that FeBr++ and FeBr2+ are formed, and values are obtained for the equilibrium constants for their formation from simple ions, and for the extinction coefficients of FeBr++. When thiocyanate is also present, the data can best be interpreted by assuming that FeSCNBr+ or FeSCNCl+ is formed. At high chloride concentrations it seems necessary to postulate also FeCl2+ and FeSCN•Cl2. Estimates are made for the equilibrium constants for the formation of all these species from simple ions. As with the corresponding sulphate complexes, there seems to be no particular reluctance to form mixed complexes such as FeSCNCl+, as compared with the 'simple' complexes such as FeCl2+.

FERRIC SULPHATE COMPLEXES, AND TERNARY COMPLEXES WITH THIOCYANATE IONS

1955 ◽  
Vol 33 (10) ◽  
pp. 1591-1602 ◽  
Author(s):  
M. W. Lister ◽  
D. E. Rivington
Keyword(s):  
Ionic Strength ◽  
Constant Temperature ◽  
Equilibrium Constants ◽  
Spectrophotometric Study ◽  
Ternary Complexes ◽  
Ferric Sulphate ◽  
Extinction Coefficients ◽  
Mixed Complexes

A spectrophotometric study of solutions containing ferric and sulphate ions, and also ferric, sulphate, and thiocyanate ions, is reported. The measurements were made at constant temperature and ionic strength; the effect of varying acidity was also investigated. The data were interpreted with the help of the results of the first paper of this series. It is believed that the data show that FeSO4+ and FeHSO4++ ions are formed. Values are obtained for the equilibrium constants for their formation from simple ions, and for their extinction coefficients. At higher sulphate concentrations there is evidence for the appearance of Fe(SO4)2− and FeSO4•HSO4, and estimates are made of their equilibrium constants. When thiocyanate is also present, the data can best be interpreted by assuming that the complex FeSO4•SCN is formed, and at higher sulphate probably also Fe(SO4)2SCN−−. Values are obtained for the equilibrium constants for the formation of these species, and the results would indicate that mixed complexes of this type are formed as readily as 'simple' ones such as Fe(SO4)2−.

SOME EQUILIBRIUM CONSTANTS OF TRANSITION METAL HALIDES

1960 ◽  
Vol 38 (10) ◽  
pp. 1827-1836 ◽  
Author(s):  
M. W. Lister ◽  
P. Rosenblum
Keyword(s):  
Ionic Strength ◽  
Transition Metal ◽  
Equilibrium Constant ◽  
Spectrophotometric Method ◽  
Equilibrium Constants ◽  
Cell Voltage ◽  
Metal Halides ◽  
Complex Ions ◽  
Anomalous Variation ◽  
A Cell

Measurements are reported on the formation of complex ions in solutions containing cupric and chloride or bromide ions, and solutions of nickel or cobalt with chloride. In each case the halide was present in very low amount. With copper a spectrophotometric method was used, and a cell voltage method with nickel and cobalt. The ionic strength was kept constant, but the temperature was varied. The data show difficulties of interpretation if it is assumed that only MX+ ions (M is the metal, X is the halogen) are formed, the difficulties arising from the anomalous variation of the equilibrium constant with temperature, and from the general drift of the calculated constants from the e.m.f. measurements. Various explanations are considered and it is shown that postulation of M2X+3 ions is at least a possible explanation.

THE DISSOCIATION OF α- AND β-LIPOVITELLIN IN AQUEOUS SOLUTION: PART I. EFFECT OF pH, TEMPERATURE, AND OTHER FACTORS

1962 ◽  
Vol 40 (3) ◽  
pp. 363-372 ◽  
Author(s):  
R. W. Burley ◽  
W. H. Cook
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Thermodynamic Data ◽  
Equilibrium Constants ◽  
Effect Of Ph ◽  
Reversible Dissociation ◽  
Lipoprotein Concentration ◽  
Irreversible Aggregation ◽  
Increasing Temperature

The effect of pH, temperature, ionic strength, and lipoprotein concentration on the reversible dissociation of α- and β-lipovitellin in aqueous solutions above pH 6 has been examined by ultracentrifugal measurements. Under otherwise similar conditions α- and β-lipovitellin are 50% dissociated at pH 10.5 and 7.8, respectively. Both lipovitellins undergo an irreversible aggregation above about pH 11; β-lipovitellin is sometimes converted to a non-dissociable form upon aging. Dissociation of both lipovitellins decreases with increasing ionic strength and increasing temperature. Although the ultracentrifugal method has limitations, provisional equilibrium constants and thermodynamic data were obtained from it that are comparable with those obtained for certain protein systems.

Spectral studies on the interaction of iodine with thiazoles

1987 ◽  
Vol 65 (3) ◽  
pp. 468-472 ◽  
Author(s):  
Refat Abdel-Hamid ◽  
Ahmed A. El-Samahy ◽  
Abdel-Hafiz El-Taher ◽  
Hussein El-Sagher
Keyword(s):  
Equilibrium Constants ◽  
Spectral Characteristics ◽  
Molecular Complexes ◽  
Spectral Studies ◽  
Donor Center ◽  
Extinction Coefficients ◽  
Effect Of Solvents ◽  
Different Temperatures ◽  
Donor Acceptor ◽  
Thermodynamic Functions Of Formation

The electron donor–acceptor molecular complexes between thiazole and some of its derivatives and iodine in several solvents have been investigated spectrophotometrically at different temperatures. Spectral characteristics, equilibrium constants, K, extinction coefficients, ε, and thermodynamic functions of formation, ΔH0, ΔG0, and ΔS0 have been determined. It was found that the data fit satisfactorily the 1:1 stoichiometric equilibrium: D + I2 = DI2 "outer complex". The EDA complexes obtained are of "n–σ*" type in which the nitrogen atom of thiazole is the donor center. Moreover, the effect of solvents on the K values is discussed in terms of the solute–solute and solute–solvent competing equilibria.

Equilibrium constants of pyridoxal 5'-phosphate Schiff bases - A polarographic study

1983 ◽  
Vol 48 (7) ◽  
pp. 1950-1955 ◽  
Author(s):  
Juan Llor ◽  
Javier Bonal ◽  
Manuel Cortijo
Keyword(s):  
Schiff Base ◽  
Ionic Strength ◽  
Equilibrium Constant ◽  
Schiff Bases ◽  
Ph Dependence ◽  
Equilibrium Constants ◽  
Constant Ionic Strength ◽  
Polarographic Study ◽  
Ionic Forms

The equilibrium constant for the formation of the Schiff base between pyridoxal 5'-phosphate and n-hexylamine has been evaluated from polarographic measurements. The pH dependence of the equilibrium constant has been investigated at constant ionic strength. The values thus obtained for the equilibrium constant compare well with those computed from the pK of the several ionic forms of pyridoxal 5'-phosphate, its Schiff base and the amine present in the solution.

scholarly journals Spectrophotometric study of time stability and acid-base characteristics of chelerythrine and dihydrochelerythrine

2010 ◽  
Vol 8 (3) ◽  
pp. 626-632 ◽  
Author(s):  
Helena Absolínová ◽  
Luděk Jančář ◽  
Irena Jančářová ◽  
Jaroslav Vičar ◽  
Vlastimil Kubáň
Keyword(s):  
Ionic Strength ◽  
Spectral Properties ◽  
Equilibrium Constants ◽  
Ionic Species ◽  
Spectrophotometric Study ◽  
Time Stability ◽  
Priority Effect ◽  
Acid Base ◽  
Strength Of Interaction ◽  
Transition Reaction

AbstractTime stability, acid-base and UV-VIS spectral properties of dihydrochelerythrine (DHCHE) were studied spectrophotometrically in water:methanol and water:ethanol media. DHCHE is stable in strongly acid milieu (pH HCl, HNO3, H2SO4, H3PO4 and their mixtures. Remarkable shifts of formation parts of absorbance-pH (A-pH) curves to the alkaline medium were observed depending on the type and concentration of inert electrolyte (most remarkable for HNO3 and HCl). The corresponding equilibrium constants pKR+ of the transition reaction between charged iminium Q+ and uncharged QOH (pseudo-base, 6-hydroxy-dihydro derivative) forms of chelerythine were calculated using a numerical interpretation of A-pH curves by a SQUAD-G computer program which ranged from 8.51–9.31. The highest changes of ΔpK R+ (0.75 and 0.53) were observed for H3PO4 and H2SO4, respectively. The priority effect of ionic species and ionic strength was confirmed in the presence of additions of NaCl and KCl. The strength of interaction of CHE with biomacromolecular compounds (i.e., peptides, proteins, nucleic acids etc.) may be affected because of the observed influence of both cation and anion of the inert electrolyte on acid-base behavior.

THE DISSOCIATION OF α- AND β-LIPOVITELLIN IN AQUEOUS SOLUTION: PART I. EFFECT OF pH, TEMPERATURE, AND OTHER FACTORS

1962 ◽  
Vol 40 (1) ◽  
pp. 363-372 ◽  
Author(s):  
R. W. Burley ◽  
W. H. Cook
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Thermodynamic Data ◽  
Equilibrium Constants ◽  
Effect Of Ph ◽  
Reversible Dissociation ◽  
Lipoprotein Concentration ◽  
Irreversible Aggregation ◽  
Increasing Temperature

The effect of pH, temperature, ionic strength, and lipoprotein concentration on the reversible dissociation of α- and β-lipovitellin in aqueous solutions above pH 6 has been examined by ultracentrifugal measurements. Under otherwise similar conditions α- and β-lipovitellin are 50% dissociated at pH 10.5 and 7.8, respectively. Both lipovitellins undergo an irreversible aggregation above about pH 11; β-lipovitellin is sometimes converted to a non-dissociable form upon aging. Dissociation of both lipovitellins decreases with increasing ionic strength and increasing temperature. Although the ultracentrifugal method has limitations, provisional equilibrium constants and thermodynamic data were obtained from it that are comparable with those obtained for certain protein systems.

The Strecker reaction — an examination in terms of no-barrier theory

2008 ◽  
Vol 86 (4) ◽  
pp. 285-289 ◽  
Author(s):  
J Peter Guthrie ◽  
Goonisetty Bhaskar
Keyword(s):  
Aqueous Solution ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Reaction Rate ◽  
Equilibrium Constants ◽  
Reaction Rate Constant ◽  
Cyanide Ion ◽  
Strecker Reaction ◽  
Rate Determining Step ◽  
Iminium Ion

For those examples of the Strecker reaction where information about both rate and equilibrium is available, we have been able to calculate rate constants for the addition of cyanide ion to the iminium ion by the no-barrier theory (NBT) approach. Both experimental and calculated values are for reaction in aqueous solution. Only for the reactions of benzaldehyde with benzyl or allyl amines and HCN are the equilibrium constants and rate constants for the final, rate-determining, step directly available from the literature. For the reactions of acetone with ammonia, methylamine, or dimethylamine and HCN rate constants for the retro-Strecker cleavage and the equilibrium constants for the overall Strecker reaction have been reported. These equilibrium constants, combined with equilibrium constants for iminium ion formation, which can be extracted from information in the literature, allow calculation of the equilibrium constants for the final step of these Strecker reactions. No-barrier theory has already been applied to carbonyl additions, including cyanohydrin formation; this report provides further evidence for the generality of this approach for calculating rate constants without using any kinetic information.Key words: Strecker reaction, rate constant, equilibrium constant, no-barrier theory, computation.

Sign in / Sign up

Export Citation Format

Share Document