Kinetics and Mechanism of the Oxidation of Dl-Methionine by Benzimidazolium Dichromate

2009 ◽  
Vol 34 (3) ◽  
pp. 199-209 ◽  
Author(s):  
Dinesh Pandey ◽  
Seema Kothari
Keyword(s):  
Solvent Effect ◽  
Dimethyl Sulfoxide ◽  
Organic Solvents ◽  
Kinetics And Mechanism ◽  
Hydrogen Ions ◽  
First Order

The oxidation of DL-methionine (MT) by benzimidazolium dichromate (BIDC), in dimethyl sulfoxide, leads to the formation of the corresponding sulfoxide. The reaction is first order with respect to BIDC. Michaelis - Menten type kinetics were observed with respect to MT. The reaction is catalysed by hydrogen ions and the dependence is of the form kobs = k‘[H+]. The rate of oxidation of MT was determined in 19 organic solvents. An analysis of the solvent effect by solvatochromic equations indicated that though both the anion- and cation-solvating powers of the solvent contribute to the observed solvent effect, the role of cation-solvation is much the major. A suitable mechanism has been proposed.

Kinetics and Mechanism of the Oxidation of Some Thioacids by Butyltriphenylphosphonium Dichromate

2007 ◽  
Vol 32 (3) ◽  
pp. 119-129 ◽  
Author(s):  
K.M. Dilsha ◽  
Seema Kothari
Keyword(s):  
Solvent Effect ◽  
Organic Solvents ◽  
Second Order ◽  
Kinetics And Mechanism ◽  
Slow Step ◽  
Hydrogen Ions ◽  
First Order

The oxidation of thioglycollic, thiolactic and thiomalic acids by butyltriphenylphosphonium dichromate (BTPPD) in dimethylsulfoxide (DMSO) yielded the corresponding disulfide as the product. The reaction is first order with respect to BTPPD, however, second-order dependences of the rate were found on the concentrations of both the thioacid and hydrogen ions. The rate of oxidation of thiolactic acid (TLA) was determined in nineteen organic solvents. An analysis of the solvent effect by multiparametric equations indicated the cation-solvating power of the solvents to be most significant. A mechanism has been proposed involving the formation of a thioester in a pre-equilibrium, followed by its decomposition in the slow step.

The kinetics and mechanism of the reaction between nickel(II) and dithiocarbamate ions in dimethyl sulfoxide. Evidence for the ID mechanism for a bidentate uninegative ligand

1978 ◽  
Vol 31 (12) ◽  
pp. 2581 ◽  
Author(s):  
PJ Nichols ◽  
MW Grant
Keyword(s):  
Fourier Transform ◽  
Ionic Strength ◽  
Dimethyl Sulfoxide ◽  
Excellent Agreement ◽  
Rate Constants ◽  
Second Order ◽  
Kinetics And Mechanism ◽  
First Order ◽  
Temperature Dependences ◽  
Mechanism Of The Reaction

13C Fourier-transform N.M.R. has been used to measure the rate of exchange of dimethyl sulfoxide with hexakis(dimethyl sulfoxide)nickel(II) cation. The parameters obtained, kex(25°C)(9.8�4.6) × 103 s-1, ΔH‡ 50�2 kJ mol-1 and ΔS‡ 0�4 J K-1 mol-1, are in excellent agreement with those of the most recent 1H N.M.R. study. The reaction between Ni(Me2SO)62+ and diethyldithiocarbamate (dtc-) gives only Ni(dtc)2. When dtc- is in excess, the rate of formation of Ni(dtc)2 is first order in Ni2+ and dtc-. The ionic-strength and temperature dependences of the second-order rate constants are consistent with the rate-determining formation of an unstable Ni(dtc)+ complex by an ID mechanism.

Exploring Baryon Rich Matter with Heavy-Ion Collisions

2019 ◽  
Vol 64 (7) ◽  
pp. 583 ◽  
Author(s):  
S. Harabasz
Keyword(s):  
Center Of Mass ◽  
Heavy Ion ◽  
State Density ◽  
Heavy Nuclei ◽  
First Order ◽  
Center Of Mass Energy ◽  
Ion Collisions ◽  
Deconfinement Phase Transition ◽  
Ground State Density

Collisions of heavy nuclei at (ultra-)relativistic energies provide a fascinating opportunity to re-create various forms of matter in the laboratory. For a short extent of time (10-22 s), matter under extreme conditions of temperature and density can exist. In dedicated experiments, one explores the microscopic structure of strongly interacting matter and its phase diagram. In heavy-ion reactions at SIS18 collision energies, matter is substantially compressed (2–3 times ground-state density), while moderate temperatures are reached (T < 70 MeV). The conditions closely resemble those that prevail, e.g., in neutron star mergers. Matter under such conditions is currently being studied at the High Acceptance DiElecton Spectrometer (HADES). Important topics of the research program are the mechanisms of strangeness production, the emissivity of matter, and the role of baryonic resonances herein. In this contribution, we will focus on the important experimental results obtained by HADES in Au+Au collisions at 2.4 GeV center-of-mass energy. We will also present perspectives for future experiments with HADES and CBM at SIS100, where higher beam energies and intensities will allow for the studies of the first-order deconfinement phase transition and its critical endpoint.

scholarly journals Metabolic Acidosis in Patients with CKD: Epidemiology, Pathogenesis, and Treatment

2021 ◽  
pp. 1-16
Author(s):  
Marcin Adamczak ◽  
Stanisław Surma
Keyword(s):  
Metabolic Acidosis ◽  
Sodium Bicarbonate ◽  
Current Knowledge ◽  
Venous Blood ◽  
The Body ◽  
Hydrogen Ions ◽  
Ckd Progression ◽  
New Drug ◽  
Treatment And Prevention

<b><i>Background:</i></b> Metabolic acidosis in CKD is diagnosed in patients with plasma or venous blood bicarbonate concentration lower than 22 mmol/L. Metabolic acidosis occurs in about 20% of patients with CKD. Metabolic acidosis may lead to dysfunction of many systems and organs as well as CKD progression. Currently, sodium bicarbonate is mainly used for pharmacological treatment of metabolic acidosis in patients with CKD. Veverimer is a new drug dedicated to treatment of metabolic acidosis in patients with CKD. Orally given veverimer binds hydrogen ions in the intestines and subsequently is excreted from the body with feces. Clinical studies have shown that veverimer is effective in increasing serum bicarbonate concentrations in CKD patients with metabolic acidosis. Here, we present review of the epidemiology, pathogenesis, diagnosis, treatment, and prevention of metabolic acidosis in CKD patients. <b><i>Summary:</i></b> Metabolic acidosis is common in patients with CKD and contributes to CKD progression and many complications, which worsen the prognosis in these patients. Currently, sodium bicarbonate is mainly used in metabolic acidosis treatment. The role of the new drug veverimer in the metabolic acidosis therapy needs further studies. <b><i>Key Message:</i></b> The aim of this review article is to summarize the current knowledge concerning the epidemiology, pathogenesis, diagnosis, treatment, and prevention of metabolic acidosis in CKD patients.

scholarly journals Investigation of the role of the C-PCM solvent effect in reactivity indices

2005 ◽  
Vol 117 (5) ◽  
pp. 583-589 ◽  
Author(s):  
Piotr Ordon ◽  
Akitomo Tachibana
Keyword(s):  
Solvent Effect ◽  
Reactivity Indices
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