The comparative chemistry of ammine and methylamine complexes of rhodium(III) and cobalt(III)

1977 ◽  
Vol 55 (17) ◽  
pp. 3166-3171 ◽  
Author(s):  
Thomas Wilson Swaddle
Keyword(s):  
Ionic Strength ◽  
Spectral Data ◽  
Electron Donor ◽  
Dissociation Constants ◽  
Base Hydrolysis ◽  
Acid Dissociation ◽  
Rate Coefficients ◽  
Acid Dissociation Constants ◽  
First Order ◽  
Kinetics Of

For the aquation of (CH3NH2)5RhCl2+, the first order rate coefficients are represented by ΔHaq* = 101.9 kJ mol−1 and ΔSaq* = −50.2 JK−1 mol−1 in 0.1 M HClO4, while for base hydrolysis the rate is first order in [(CH3NH2)5RhCl2+] and [OH−] at ionic strength 0.10 M and the rate coefficients (in M−1 s−1) are represented by ΔHOH*> = 108.6 kJ mol−1 and ΔSOH* = 74.1 J K−1 mol−1. Acid dissociation constants are reported for (RNH2)5MOH23+ (R = H or CH3; M = Rh or Co), and these, combined with spectral data, show CH3NH2 to be a poorer electron donor than NH3 in complexes of this type, contrary to expectations. The comparative kinetics of reactions of (RNH2)5MCl2+ support the assignment of an Ia mechanism to aquation when M = Rh or Cr, Id to aquation when M = Co, and Dcb for base hydrolysis in all these cases.

Pyridine nitrosazones and their cobalt(III) chelates

1977 ◽  
Vol 55 (21) ◽  
pp. 3707-3711 ◽  
Author(s):  
Ahmad Sami Shawali ◽  
Ikhlass M. Abbass
Keyword(s):  
Ionic Strength ◽  
Spectral Data ◽  
Dissociation Constants ◽  
Ring Structure ◽  
Membered Ring ◽  
Acid Dissociation ◽  
Acid Dissociation Constants ◽  
Transition Energies ◽  
Amyl Nitrite ◽  
Good Agreement

Nitrosation of pyridine aldehyde p-tolylhydrazones 2 with amyl nitrite gives rise to p-tolueneazopyridine aldoximes 4 which form stable tris chelates with cobalt(III). Spectral data (ir, uv, and 1Hmr) indicate that the ligands exist mainly in the assigned azooxime structure 4, and that their chelates have five-membered ring structure 7. Also, the 1Hmr spectra imply mer-configuration 9 for the chelates examined. No evidence for the tautomeric nitrosohydrazone structure 3 for the ligands and the fac-configuration 8 for Co(III) chelates could be obtained. Using the HMO method, the azooxime form 4 for the ligand was shown to be more stable than the nitrosohydrazone structure 3. Also, good agreement was obtained between observed transition energies and those calculated by the HMO method. The acid dissociation constants of the ligands in 50 vol% ethanol–water at 25 °C and ionic strength of 0.1 were determined spectrophotometrically.

Studies on Lactoperoxidase. VI. Kinetics of the Oxidation of p-Cresol by Compound II

1973 ◽  
Vol 51 (11) ◽  
pp. 1721-1723 ◽  
Author(s):  
R. James Maguire ◽  
H. Brian Dunford
Keyword(s):  
Dissociation Constants ◽  
Acid Dissociation ◽  
Stopped Flow ◽  
Acid Dissociation Constants ◽  
First Order ◽  
Diffusion Controlled ◽  
Ph Range ◽  
Rate Profile ◽  
Compound Ii ◽  
Kinetics Of

The kinetics of the oxidation of p-cresol by compound II of lactoperoxidase have been studied over the pH range 2.1–11.2 by the stopped-flow technique. The reaction is kinetically first-order with respect to p-cresol over the entire pH range. Use is made of the diffusion-controlled limit that can be placed on a bimolecular rate constant to show that p-cresol reacts in the unionized form. The complexity of the pH-rate profile is discussed in terms of acid dissociation constants of groups in the enzyme and the ionization of the substrate.

scholarly journals The equilibrium constant of the phosphoglyceromutase reaction

1974 ◽  
Vol 139 (3) ◽  
pp. 491-497 ◽  
Author(s):  
John B. Clarke ◽  
Michael Birch ◽  
Hubert G. Britton
Keyword(s):  
Ionic Strength ◽  
Equilibrium Constant ◽  
Dissociation Constants ◽  
Ph Dependence ◽  
Binding Constants ◽  
Acid Dissociation ◽  
Effect Of Temperature ◽  
Acid Dissociation Constants ◽  
The Difference ◽  
Low Ionic Strength

The equilibrium constant of the phosphoglyceromutase reaction was determined over a range of pH (5.4–7.9), in solutions of different ionic strength (0.06–0.3) and in the presence of Mg2+, at 30°C and at 20°C. The values obtained (8.65–11.65) differ substantially from previously published values. The third acid dissociation constants were redetermined for 2- and 3-phosphoglycerate, and in contrast with previous reports the pK values (7.03 and 6.97 respectively at zero ionic strength) were closely similar. The Mg2+-binding constants were measured spectrophotometrically and the values, 286mm-1 and 255mm-1 for 2- and 3-phosphoglycerate at pH7 and ionic strength 0.02, were also very similar. From the relative lack of effect of temperature, pH and ionic strength it is concluded that the equilibrium constant differs from unity largely because of entropic factors. At low ionic strength, in the neutral region, the pH-dependence can be attributed to the small difference in the acid dissociation constants, but the difference in dissociation constants does not explain the pH-dependence in the acid region or at high ionic strength. Within physiological ranges of pH, Mg2+ concentration and ionic strength there will be little variation in equilibrium constant.

Kinetics of acid-catalysed hydrolysis of the α and β Carbonato(4,7-dimethyltriethylenetetramine) cobalt(III) ions

1974 ◽  
Vol 27 (2) ◽  
pp. 269 ◽  
Author(s):  
DJ Francis ◽  
GH Searle
Keyword(s):  
Acid Hydrolysis ◽  
Perchloric Acid ◽  
Rate Constants ◽  
Dissociation Constants ◽  
Bond Cleavage ◽  
Acid Dissociation ◽  
Acid Dissociation Constants ◽  
Rate Laws ◽  
Kinetics Of ◽  
Hydrolysis Of

The synthesis and separation of the complexes α-[Co(dmtr)CO3] ClO4 and β-[Co(dmtr)CO3] C1O4,H2O (dmtr = 4,7-dimethyltriethylenetetramine or N,N'-bis(2-aminoethyl)-N,N'-dimethylethane-1,2-diamine) are described. The kinetics of the acid hydrolysis of both complexes, studied in perchloric acid at 25�C and μ = 1.0M (LiC1O4), follow rate laws of form -d[complex]dt=(k0 + k1[H+I)[complex] The values of ko and k1 for the K-complex are 1.0 x 10-3 s-1 and 1.8 x 10-2 1. mol-1 s-1 respectively, while for the β-complex the corresponding values are 3.6 x 10-5 s-1 and 5.6 x 10-4 1. mol-1 s-1. Comparisons of these rate constants with the values for similar carbonato(tetramine)cobalt(111) complexes previously studied suggest that the ko path could involve O-C bond cleavage in the present dmtr complexes. The values of the acid dissociation constants of dmtr,4HCl, determined by potentiometric titration, are 1.61, 5.86, 8.18 and 9.95.

scholarly journals The Kinetics of Chitosan Degradation in Organic Acid Solutions

Marine Drugs ◽  
2021 ◽  
Vol 19 (5) ◽  
pp. 236
Author(s):  
Dominik Sikorski ◽  
Karolina Gzyra-Jagieła ◽  
Zbigniew Draczyński
Keyword(s):  
Organic Acid ◽  
Dissociation Constants ◽  
Degradation Process ◽  
Acid Dissociation ◽  
Acid Solutions ◽  
Spectroscopy Analysis ◽  
Acid Dissociation Constants ◽  
Spinning Process ◽  
Kinetics Of ◽  
Selection Of

This paper presents a comparative study on chitosan degradation in organic acid solutions according to their different dissociation characteristics. More precisely, the aim of the study was to determine the kinetics of the degradation process depending on the different acid dissociation constants (pKa values). The scientists involved in chitosan to date have focused mainly on acetic acid solutions. Solutions of lactic, acetic, malic, and formic acids in concentrations of 3% wt. were used in this research. The progress of degradation was determined based on the intrinsic viscosity measurement, GPC/SEC chromatographic analysis, and their correlation. Changes in the viscosity parameters were performed at a temperature of 20 °C ± 1 °C and a timeframe of up to 168 h (7 days). The chemical structure and DDA of the initial chitosan were analyzed using 1H-NMR spectroscopy analysis. The results of this study can be considered of high importance for the purpose of electrospinning, production of micro- and nano-capsules for drug delivery, and other types of processing. Understanding the influence of the dissociation constant of the solvent on the kinetics of chitosan degradation will allow the selection of an appropriate medium, ensuring an effective and stable spinning process, in which the occurrence of polymer degradation is unfavorable.

Kinetics and Mechanism of Hexachloroiridate(IV) Oxidation of Arsenic(III) in Acidic Perchlorate Solutions

1992 ◽  
Vol 57 (7) ◽  
pp. 1451-1458 ◽  
Author(s):  
Refat M. Hassan
Keyword(s):  
Ionic Strength ◽  
Fractional Order ◽  
Activation Parameters ◽  
Order Reaction ◽  
First Order Reaction ◽  
Intermediate Complex ◽  
Constant Ionic Strength ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Kinetics Of

The kinetics of oxidation of arsenic(III) by hexachloroiridate(IV) at lower acid concentrations and at constant ionic strength of 1.0 mol dm-3 have been investigated spectrophotometrically. A first-order reaction in [IrCl62-] and fractional order with respect to arsenic(III) have been observed. A kinetic evidence for the formation of an intermediate complex between the hydrolyzed arsenic(III) species and the oxidant was presented. The results showed that decreasing the [H+] is accompanied by an appreciable acceleration of the rate of oxidation. The activation parameters have been evaluated and a mechanism consistent with the kinetic results was suggested.

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