scholarly journals Thermodynamic and detailed kinetic study of the formation of orthophthalaldehyde-agmatine complex by fluorescence intensities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Khémesse Kital ◽  
Moumouny Traoré ◽  
Diégane Sarr ◽  
Moussa Mbaye ◽  
Mame Diabou Gaye Seye ◽  
...  
Keyword(s):  
Complex Formation ◽  
Thermodynamic Parameters ◽  
Initial Rate ◽  
Reaction Medium ◽  
Standard Entropy ◽  
Step Size ◽  
Formation Reaction ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Complex Formation Process

Abstract The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°),and Gibbs energy (∆G) were calculated, where a positive value of ΔH° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ΔS°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ΔG between −35.62 kJ/mol and −26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10−6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10−7Mmin−1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.

Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

1977 ◽  
Vol 16 (01) ◽  
pp. 30-35 ◽  
Author(s):  
N. Agha ◽  
R. B. R. Persson
Keyword(s):  
Complex Formation ◽  
Significant Influence ◽  
Room Temperature ◽  
Ph Value ◽  
Maximum Activity ◽  
Reduction Step ◽  
Labelling Yield ◽  
Different Temperatures ◽  
Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

Kinetic and spectrophotometric studies of binding of iron(III) by glutathione

1976 ◽  
Vol 54 (20) ◽  
pp. 3192-3199 ◽  
Author(s):  
Tahir R. Khan ◽  
Cooper H. Langford
Keyword(s):  
Complex Formation ◽  
Kinetic Method ◽  
Binding Constants ◽  
Chelating Agent ◽  
Formation Reaction ◽  
Spectrophotometric Data ◽  
Natural Water Chemistry ◽  
Kinetics Of ◽  
Sulfur Containing

In this report, determination of unbound aquo iron species is accomplished by a kinetic method involving reaction with sulfosalicylic acid (SSA) on a time scale which is very short with respect to reaction of SSA with the glutathione complexes of iron. The data are used to calculate conditional binding constants for Fe(III) to glutathione. Binding constants in 0.1 M ionic strength media were obtained between pH 1 and 2.4 by the kinetic method, and near pH = 3 by spectrophotometry and by examination of the ratio of rate of complex formation and dissociation. The conditional binding 'constant' between pH 1 and 3 is represented as pK = −1.96 – 0.50pH. This is consistent with the importance of reactions involving only very limited proton release. Spectrophotometric data show that the —OH group on Fe(OH)2+ is lost on glutathione complexing. Kinetics of the complex formation reaction between aquo iron(III) species and glutathione are slower than rates of reaction of iron(III) with simple ligands.The glutathione system is regarded as a model system important to natural water chemistry because it is a widely distributed biological sulfur-containing chelating agent.

Kinetics and Mechanism of the 2+ 2 Cycloaddition of Tetracyanoethylene to 2,5-Dimethyl-2,4-Hexadiene

1988 ◽  
Vol 43 (5) ◽  
pp. 435-441 ◽  
Author(s):  
Adel N. Asaad ◽  
Gunnar Aksnes
Keyword(s):  
Complex Formation ◽  
Transition State ◽  
Thermodynamic Parameters ◽  
Cycloaddition Reaction ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Kinetics And Mechanism ◽  
Eda Complex ◽  
Kinetics Of ◽  
Cyclobutane Derivative

The kinetics of the 2 + 2 cycloaddition reaction between tetracyanoethylene and 2,5-dimethyl- 2,4-hexadiene in different solvents has been studied by following the disappearance of the intermediate EDA-complex spectrophotometrically. It is concluded that the EDA-complex is transformed through a concerted cyclicpolar transition state to give the vinyl cyclobutane derivative (III). The effects of various solvents on the reaction rates have been analysed using a multiparameter approach. The thermodynamic parameters (ΔH0 and ΔS0), of EDA-complex formation and the activation parameters (ΔH# and ΔS#) of the cycloaddition have been discussed.

scholarly journals Cordination Compound of Dimethyltin(IV) with N,N,N’N’-Tetraethylethylenediamine: Speciation and Theoretical approach

2020 ◽  
Vol 64 (2) ◽  
Author(s):  
Safaa Said Hassan ◽  
Mohamed Mohamed Shoukry ◽  
Abdel Aziz Qasem Jbarah
Keyword(s):  
Complex Formation ◽  
Vibrational Frequencies ◽  
Geometric Optimization ◽  
Binding Energies ◽  
Formation Reaction ◽  
Calculated Binding Energy ◽  
B3lyp Method ◽  
Different Temperatures ◽  
Formation Equilibria ◽  
Optimized Geometries

The formation equilibria of the dimethyltin(IV) complexes with of N,N,N’,N’-tetraethylethylenediamine (Et4en) in solution were investigated. The stoichiometry and stability constants of the complexes formed in solution phase were determined at different temperatures (15 oC – 35 oC) and in solutions of dioxane-water mixtures of different compositions (15% - 62.5%). The accepted model is composed of the 110, 111, 11-1 and 11-2 species. The thermodynamic parameters H and S associated with the protonation of N,N,N`,N`-tetraethylethylendiamine (Et4en) and its complex formation with the dimethyltin(IV) species were determined. The complex formation reaction is exothermic. The equilibrium constant for the displacement of N,N,N’,N’-tetraethylethylenediamine coordinated to dimethyltin(IV) by some selected DNA constituents was calculated. The Keq values clearly indicate the ability of DNA to displace the coordinated Et4en from its dimethyltin(IV) complex. The nucleotides IMP and GMP have the highest values. The DFT/B3LYP method was used for geometric optimization of the ligand and the complex using the Gaussian 09 program. Also the vibrational frequencies of the ligands and complexes were computed for the optimized geometries. The results shows that there is no imaginary frequencies as found in the calculated vibrational frequencies. The binding energies of the dimethyltin(IV) complexes were calculated. All calculated binding energy values are negative.

scholarly journals Kinetics of Oxidation of Metochlopramide withChloramine-T in HClO4 Medium

2009 ◽  
Vol 6 (2) ◽  
pp. 545-552 ◽  
Author(s):  
K. M. Meenakshi ◽  
K. Vasant Kumar Pai
Keyword(s):  
Thermodynamic Parameters ◽  
Fractional Order ◽  
Reaction Rate ◽  
Oxidation Products ◽  
Perchloric Acid Solution ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Different Temperatures ◽  
Negative Effect ◽  
Kinetics Of

The kinetics of oxidation of metochlopramide hydrochloride (MCP) with sodiumN-chlorop-toluenesulfonamide (CAT) in perchloric acid solution has been studied at 313K. The reaction rate shows a first order dependence on [CAT], fractional order on [MCP] and inverse fractional order on [H+]. There is a negative effect of dielectric constant of the solvent. The addition of the reduction product of CAT has no significant effect on the rate. The rate remained unchanged with the variation in the ionic strength of the medium. The reaction fails to induce the polymerization of acrylonitrile. Thermodynamic parameters have been computed by Arrhenius plot. The stoichiometry of the reaction was found to be 1:2 and oxidation products were identified. The Michaelis-Menten type of kinetics has been proposed. CH3C6H4SO2NHCl have been assumed to be the reactive oxidizing species. Thermodynamic parameters were computed by studying reactions at different temperatures. A mechanism consistent with observed kinetics is proposed.

scholarly journals Deviation from Michaelis-Menten kinetics for fumarase

1976 ◽  
Vol 157 (2) ◽  
pp. 333-337 ◽  
Author(s):  
M J Crabbe ◽  
W G Bardsley
Keyword(s):  
Steady State ◽  
Complex Formation ◽  
Initial Rate ◽  
Fourth Degree ◽  
Complex Curve ◽  
Steady State Kinetics ◽  
Dead End ◽  
High Degree ◽  
Kinetics Of ◽  
Aggregation Phenomena

A study of the steady-state kinetics of fumarase over an extended concentration range, using novel methods of analysis, reveals an initial-rate equation of at least fourth degree for malate as substrate at pH 7.0, with no kinetically significant dead-end complex formation even up to concentrations of 100 mM. In the absence of demonstrable enzyme-aggregation phenomena, this is interpreted as indicating co-operative effects overlooked previously, although a mixture of isoenzymes, each individually of high degree and giving a complex curve, may be a contributing factor.

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