scholarly journals Kinetic and Mechanistic Studies on the Reaction of DL-Methionine with in Aqueous Medium at Physiological pH

2009 ◽  
Vol 2009 ◽  
pp. 1-5 ◽  
Author(s):  
Tandra Das ◽  
A. K. Datta ◽  
A. K. Ghosh
Keyword(s):  
Temperature Dependence ◽  
Aqueous Medium ◽  
Equilibrium Constant ◽  
Thermodynamic Parameters ◽  
Activation Parameters ◽  
Outer Sphere ◽  
Ligand Concentration ◽  
Mechanistic Studies ◽  
Association Equilibrium

The reaction has been studied spectrophotometrically; the reaction shows two steps, both of which are dependent on ligand concentration and show a limiting nature. An associative interchange mechanism is proposed. Kinetic and activation parameters ( and ) and (, , , and ) have been calculated. From the temperature dependence of the outer sphere association equilibrium constant, thermodynamic parameters ( and ; and ) have also been calculated.

Interaction of Glycyl – Glycine with Hydroxopentaaquarhodium(Iii) Ion in Aqueous Medium: Kinetic and Mechanistic Studies

2011 ◽  
Vol 36 (4) ◽  
pp. 371-384 ◽  
Author(s):  
Biplab K. Bera ◽  
Subhasis Mallick ◽  
Arup Mandal ◽  
Subala Mondal ◽  
Parnajyoti Karmakar ◽  
...  
Keyword(s):  
Aqueous Medium ◽  
Spectroscopic Analysis ◽  
Activation Parameters ◽  
Outer Sphere ◽  
Interaction Processes ◽  
G Value ◽  
Kinetics Of ◽  
Association Equilibrium ◽  
Association Complex ◽  
Glycyl Glycine

The kinetics of interaction between glycyl-glycine (L-L'H) and[Formula: see text] [Rh(H2O)5OH] 2+ have been studied spectrophotometrically in aqueous medium as a function of [Rh(H2O)5OH] 2+], [glycyl - glycine], pH and temperature at constant ionic strength. At pH 4.3, the interaction with glycyl-glycine shows two parallel paths: both processes are ligand-dependent. The rate constant for the processes are: k1 ∼ 10 −3 s −1 and k2∼10−5 s−3. The activation parameters calculated from Eyring plots are: ΔH1≠ - 26.7 ± 0.3 kj mol−1, ΔS1≠ =-207+1 JK−1 mol−1, ΔH2≠ = 92.4 ± 1.3 kJ mol−1 and ΔS2≠ = −42±4 JK−1 mol−1. The ligand glycyl-glycine, with different donor atoms (N and O), attacks two rhodium(III) ions (Rh(III) being a borderline acid), with different reactivity. Based on the kinetic and activation parameters, an associative interchange mechanism is proposed for both interaction processes. From the temperature dependence of the outer-sphere association equilibrium constant, the thermodynamic parameters calculated are: ΔH1∘ = 21.8 ± 1.9 kJ mol−1, ΔS1∘ = 124± 6 JK−1 mol−1, ΔH2∘ = 12.7 ±0.5 kj mol−1 and ΔS2∘ 89±2 JK−1 mol″−1 which give a negative A G° value for both the steps at all temperatures studied, supporting the spontaneous formation of an outer- sphere association complex for both the parallel paths. The product of the reaction has been characterized from IR and ESI-mass spectroscopic analysis.

scholarly journals Mechanistic Aspects of Ligand Substitution on the Cis-Diaqua-Chloro-Tris(Dimethyl Sulfoxide)Ruthenium(II) Complex by Some Sulfur-Containing Bioactive Ligands in Aqueous Medium

2018 ◽  
Vol 43 (3-4) ◽  
pp. 274-285
Author(s):  
Animesh Chattopadhyay ◽  
Anwesha Dey ◽  
Parnajyoti Karmakar ◽  
Sumon Ray ◽  
Debabrata Nandi ◽  
...  
Keyword(s):  
Water Molecule ◽  
Dimethyl Sulfoxide ◽  
Aqueous Medium ◽  
Activation Parameters ◽  
Outer Sphere ◽  
Ring Closure ◽  
Bioactive Ligands ◽  
Experimental Findings ◽  
Job's Method ◽  
Sulfur Containing

The synthesis and interactions of the cis-diaqua-chloro-tris(dimethyl sulfoxide)ruthenium(II) complex with selected sulfur-containing ligands such as 2-thiouracil, glutathione and L-cysteine have been studied by UV-Vis spectrophotometry in aqueous medium at pH 4.5. From experimental data it is clear that all three reactions proceed via two steps: the first one being a rate-limiting ligand-dependent replacement of one water molecule, followed by a ligand-independent ring closure step with the expulsion of the second water molecule. The substituted products have been characterised by Job's method, FTIR spectroscopy and electrospray ionisation mass spectrometry. Activation parameters (Δ H≠ and Δ S≠) and thermodynamic parameters (Δ H0 and Δ S0, from the temperature dependence of the outer-sphere association equilibrium constant) are presented. Consistent with the experimental findings, an associative interchange mechanism is proposed.

scholarly journals ThermoSlope: A Software for Determining Thermodynamic Parameters from Single Steady-State Experiments

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7155
Author(s):  
Bjarte Aarmo Lund ◽  
Bjørn Olav Brandsdal
Keyword(s):  
Temperature Dependence ◽  
Thermodynamic Parameters ◽  
Enzyme Catalysis ◽  
Traditional Approach ◽  
Extreme Environments ◽  
Valence Bond ◽  
Activation Parameters ◽  
Gradual Change ◽  
Empirical Valence Bond ◽  
Wide Range

The determination of the temperature dependence of enzyme catalysis has traditionally been a labourious undertaking. We have developed a new approach to the classical Arrhenius parameter estimation by fitting the change in velocity under a gradual change in temperature. The evaluation with a simulated dataset shows that the approach is valid. The approach is demonstrated as a useful tool by characterizing the Bacillus pumilus LipA enzyme. Our results for the lipase show that the enzyme is psychrotolerant, with an activation energy of 15.3 kcal/mol for the chromogenic substrate para-nitrophenyl butyrate. Our results demonstrate that this can produce equivalent curves to the traditional approach while requiring significantly less sample, labour and time. Our method is further validated by characterizing three α-amylases from different species and habitats. The experiments with the α-amylases show that the approach works over a wide range of temperatures and clearly differentiates between psychrophilic, mesophilic and thermophilic enzymes. The methodology is released as an open-source implementation in Python, available online or used locally. This method of determining the activation parameters can make studies of the temperature dependence of enzyme catalysis more widely adapted to understand how enzymes have evolved to function in extreme environments. Moreover, the thermodynamic parameters that are estimated serve as functional validations of the empirical valence bond calculations of enzyme catalysis.

Kinetics and mechanism of redox reactions of U(III) ions with monochloroacetic and dichloroacetic acids

1979 ◽  
Vol 44 (2) ◽  
pp. 401-405 ◽  
Author(s):  
Ľubica Adamčíková ◽  
Ľudovít Treindl
Keyword(s):  
Redox Reactions ◽  
Reaction Rate ◽  
Activation Parameters ◽  
Outer Sphere ◽  
Alcohol Concentration ◽  
Kinetics And Mechanism ◽  
Solvent Structure ◽  
Influence Of Ph ◽  
Sphere Mechanism

The kinetics and mechanism of the redox reactions of U3+ ions with mono- and dichloroacetic acids were studied. The influence of pH was observed mainly in the second case and led to the determination of the rate constants and activation parameters corresponding to two parallel steps, namely oxidation of U3+ with CHCl2COO- ions and oxidation of U3+ with CHCl2.COOH molecules. The influence of binary mixtures of water with methanol, ethanol, isopropanol, or tert-butenol on the reaction rate was followed. Increasing alcohol concentration influences the rate constant not only through changing dielectric constant and solvation of the reactants but also through a change of the solvent structure which plays a role in reactions with an outer sphere mechanism of the electron transfer.

TI/PIMC METHOD WITH THE TAKAHASHI–IMADA APPROXIMATION FOR THE EQUILIBRIUM CONSTANT OF THE O + HCl ⇌ OH + Cl REACTION

2013 ◽  
Vol 12 (04) ◽  
pp. 1350026 ◽  
Author(s):  
MARCIN BUCHOWIECKI
Keyword(s):  
Monte Carlo ◽  
Temperature Dependence ◽  
Equilibrium Constant ◽  
Path Integral ◽  
Thermodynamic Integration ◽  
Partition Functions ◽  
Integration Path ◽  
Path Integral Monte Carlo

The thermodynamic integration/path integral Monte Carlo (TI/PIMC) method of calculating the temperature dependence of the equilibrium constant quantum mechanically is applied to O + HCl ⇌ OH + Cl reaction. The method is based upon PIMC simulations for energies of the reactants and the products and subsequently on thermodynamic integration for the ratios of partition functions. PIMC calculations are performed with the primitive approximation (PA) and the Takahashi–Imada approximation (TIA).

Adsorption of Ni (II) from Aqueous Solution Based on Porous Magnetic/Chitosan Resin

2014 ◽  
Vol 936 ◽  
pp. 829-833
Author(s):  
Hai Song ◽  
Xing Hai Yu ◽  
Xiao Qin Zhang ◽  
Gui Fang Yan ◽  
Yuan Zhi Zhen
Keyword(s):  
Aqueous Solution ◽  
Aqueous Medium ◽  
Thermodynamic Parameters ◽  
Adsorption Process ◽  
Low Cost ◽  
Second Order ◽  
Magnetic Chitosan ◽  
Spontaneous Process ◽  
Chitosan Resin ◽  
Kinetics And Thermodynamic

The purpose of this work is to prepare a low-cost biosorbent,Porous Magnetic/Chitosan Resin(MCR), and determine the ability of this biosorbent to removing Ni (II) ion from aqueous medium. Both kinetics and thermodynamic parameters of the adsorption process were also estimated. The thermodynamic parameters indicated an exothermic spontaneous process and the kinetics followed the second-order adsorption process.

Sign in / Sign up

Export Citation Format

Share Document