Thermal Decomposition of Aromatic Thioureas [1]

1986 ◽  
Vol 41 (1) ◽  
pp. 101-104 ◽  
Author(s):  
Cyril Párkányi ◽  
Mohammed A. Al-Salamah
Keyword(s):  
Thermal Decomposition ◽  
Hydrogen Transfer ◽  
Chemical Reactivity ◽  
Order Reaction ◽  
First Order ◽  
Reactivity Indices ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Intramolecular Hydrogen ◽  
Rate Limiting

Thermal decomposition of aromatic and heteroaromatic thioureas in boiling chlorobenzene is a first-order reaction. The reaction involves intramolecular hydrogen transfer followed by a cleavage of the C - N bond which is the rate-limiting step. The rate constants of decom position have been determined and correlated with quantum-chemical reactivity indices.

scholarly journals Kinetic modelling of hydrogen transfer deoxygenation of a prototypical fatty acid over a bimetallic Pd60Cu40 catalyst: an investigation of the surface reaction mechanism and rate limiting step

2020 ◽  
Vol 5 (9) ◽  
pp. 1682-1693
Author(s):  
Kin Wai Cheah ◽  
Suzana Yusup ◽  
Martin J. Taylor ◽  
Bing Shen How ◽  
Amin Osatiashtiani ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Reaction Mechanism ◽  
Hydrogen Transfer ◽  
Surface Reaction ◽  
Kinetic Modelling ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Cu Catalyst ◽  
P Application ◽  
Rate Limiting

Application of tetralin as a source of hydrogen for catalytic conversion of oleic acid to diesel-like hydrocarbons using a bimetallic Pd–Cu catalyst.

Oxidation of 1- and 2-acetylnaphthalenes by iodate - a kinetic study

1990 ◽  
Vol 55 (6) ◽  
pp. 1535-1540 ◽  
Author(s):  
Prerepa Manikyamba
Keyword(s):  
Solvent Effect ◽  
Enol Form ◽  
Aqueous Methanol ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Carbonium Ion ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics of oxidation of 1- and 2-acetylnaphthalenes by iodate in the presence of sulphuric acid in aqueous methanol has been studied. The reaction is first order with respect to both [iodate] and [acetylnaphthalene]. Solvent effect indicates a cation-dipole type of interaction in the rate limiting step. A mechanism is proposed with a slow attack of IO2+ on enol form of acetylnaphthalene forming an intermediate carbonium ion, which ultimately gives corresponding ω-hydroxyacetylnaphthalene. The higher reactivity of 2-acetyl isomer is attributed to the greater stability of the corresponding carbonium ion than that of 1-acetyl isomer.

Physical Modeling of Backside Gettering

1984 ◽  
Vol 36 ◽  
Author(s):  
Gary B. Bronner ◽  
James D. Plummer
Keyword(s):  
Experimental Data ◽  
Physical Modeling ◽  
Equilibrium Concentration ◽  
Order Model ◽  
Phosphorus Diffusion ◽  
First Order ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Buried Layer ◽  
Rate Limiting

ABSTRACTTo understand gettering action we have modeled the diffusion of metal to a backside getter. A first order model describing the diffusion of metals to an infinite backside sink is found not to fit experimental data. To fit the data for phosphorus gettering at 1000°C and argon implantation gettering at 800°C it is necessary to also hypothesize the injection of silicon interstitials. Assuming that the diffusion of the silicon interstitials is the rate limiting step in gettering, allows one to extract the diffusion coefficient and equilibrium concentration of the interstitial. The hypothesis of silicon interstitial injection agrees with recent work on phosphorus diffusion by Fahey et. al. To test this hypothesis for heavily damaged regions we have looked at the effect of an argon implanted region on the diffusion of a phosphorus buried layer. At both 800°C and 700°C, during nitrogen anneals we see significant enhancement of the phosphorus diffusion.

scholarly journals The carboxybiotin complex of pyruvate carboxylase. A kinetic analysis of the effects of Mg2+ ions on its stability and on its reaction with pyruvate

1984 ◽  
Vol 219 (1) ◽  
pp. 243-251 ◽  
Author(s):  
P V Attwood ◽  
J C Wallace ◽  
D B Keech
Keyword(s):  
Pyruvate Carboxylase ◽  
General Scheme ◽  
Order Rate Constant ◽  
Enzymic Activity ◽  
Slow Phase ◽  
First Order ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Pseudo First Order ◽  
Rate Limiting

The enzyme-[14C] carboxybiotin complex of sheep liver pyruvate carboxylase was isolated and the reaction between this and pyruvate was studied by using the quenched-flow rapid-reaction technique. At 0.5 degrees C the reaction was 80% complete within 180 ms. The reaction was monophasic and obeyed pseudo-first-order kinetics. Increasing concentrations of Mg2+ caused a decrease in the magnitude of the observed pseudo-first-order rate constant. Throughout the carboxylation of pyruvate, the rate-limiting step of the reaction occurred after the dissociation of carboxybiotin from the first sub-site, whereas in the slow phase of the reaction with 2-oxobutyrate this dissociation is the rate-limiting step. It is possible, from the reaction scheme proposed, that the inhibition of overall enzymic activity by high concentrations of Mg2+ could be caused by the transfer of the carboxy group from biotin to pyruvate becoming rate-limiting. The efficacy of a substrate as a signal for the movement of carboxybiotin from the first sub-site is reflected by the amount that the effective affinity of the enzyme- carboxybiotin complex for Mg2+ is lowered. In the presence of the substrates tested, the affinities of the carboxybiotin complex can be arranged in order of increasing magnitude, i.e.: (formula; see text). The kinetics of the decay of the enzyme-[14C] carboxybiotin complex at 0 degree C in the absence of substrates are similar to the reaction with pyruvate except that the carboxybiotin is also unstable in the first sub-site, to some degree. This similarity allows for the proposal of a general scheme for the decarboxylation of the enzyme- carboxybiotin complex in the presence or in the absence of substrates.

scholarly journals Removal of copper from an electroplating industrial effluent using the native and modified spirogyra

2018 ◽  
Vol 78 (1) ◽  
pp. 147-155 ◽  
Author(s):  
Nimra Ilyas ◽  
Sadia Ilyas ◽  
Sajjad-ur-Rahman ◽  
Sidra Yousaf ◽  
Aqsa Zia ◽  
...  
Keyword(s):  
Industrial Effluent ◽  
Order Kinetic ◽  
Sorption Data ◽  
Freundlich Model ◽  
First Order ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Intra Particle Diffusion ◽  
Pseudo Second Order ◽  
Rate Limiting

Abstract In the present study, biosorption behavior of a green filamentous alga, spirogyra in its native and modified states was investigated for copper removal from an electroplating industrial effluent. For this, the effluent containing 194 mg·L−1 Cu2+ in sulfate medium was contacted with both forms of spirogyra, under the parametric variations of effluent pH, adsorbent dosage, contact time, and sorption temperature. The study revealed spirogyra as a prominent candidate for removing contaminant metal cation; however, at the same condition, biosorption capacity of modified biomass in gel form was higher than the native spirogyra. At the optimized condition with 6 g sorbent dosage treated to 100 mL effluent for 30 min at pH 6.0 and temperature 20 °C, the maximum 82.8% and 96.4% copper could be adsorbed by the native and modified spirogyra, respectively. The batch sorption data using native biomass followed pseudo-first-order kinetic; exhibiting the multilayer sorption mechanism via surface diffusion could be defined by the Freundlich model. In contrast, the sulfuric acid treated modified spirogyra followed pseudo-second-order kinetics and intra particle diffusion as the rate-limiting step.

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

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