Substitution kinetics of paramagnetic iron(O) nitrosyl complexes. Temperature dependence of the Arrhenius activation energy

1970 ◽  
Vol 92 (22) ◽  
pp. 6425-6429 ◽  
Author(s):  
Giuseppe. Distefano ◽  
Salvatore. Pignataro ◽  
A. Foffani
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Arrhenius Activation Energy ◽  
Nitrosyl Complexes ◽  
Kinetics Of

Correlation analysis of reactivity in the addition of substituted benzylamines to β-nitrostyrene

1996 ◽  
Vol 74 (4) ◽  
pp. 625-629 ◽  
Author(s):  
Neeta Jalani ◽  
Seema Kothari ◽  
Kalyan K. Banerji
Keyword(s):  
Activation Energy ◽  
Correlation Analysis ◽  
Rate Constant ◽  
Steric Hindrance ◽  
Nucleophilic Addition ◽  
Regression Coefficients ◽  
Nucleophilic Attack ◽  
Arrhenius Activation Energy ◽  
First Order ◽  
Kinetics Of

The kinetics of addition of a number of ortho-, meta-, and para-substituted benzylamines to β-nitrostyrene (NS) in acetonitrile have been studied. The reaction is first order with respect to NS. The order with respect to the amine is higher than one. It has been shown that the reaction follows two mechanistic pathways, uncatalyzed and catalyzed by the amine. The Arrhenius activation energy for the catalyzed path is negative, indicating the presence of a pre-equilibrium (k1, k−1) leading to the formation of a zwitterion. The values of the rate constant, k1, for the nucleophilic attack have been determined for 28 benzylamines. The rate constant k1 was subjected to correlation analysis using Charton's LDR and LDRS equations. The polar regression coefficients are negative, indicating the formation of a cationic species in the transition state. The reaction is subject to steric hindrance by ortho substituents. Key words: nucleophilic addition, benzylamines, correlation analysis, kinetics, alkene.

scholarly journals Транспортные процессы с участием атомов углерода между поверхностью и объемом родия при образовании и разрушении графена

2020 ◽  
Vol 54 (6) ◽  
pp. 552
Author(s):  
Е.В. Рутьков ◽  
Е.Ю. Афанасьева ◽  
Н.Р. Галль
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Temperature Dependence ◽  
Atomic Carbon ◽  
Graphene Growth ◽  
Carbon Dissolution ◽  
The Difference ◽  
Kinetics Of

Equilibrium transport of atomic carbon between Rh surface and bulk has been studied. This transport controls the kinetics of the phase transition resulting in graphene growth or destruction. The difference ΔE=0.7 eV has been measured between the activation energy of atomic carbon dissolution E1s and that of its segregation from the bulk to the surface E1s. The temperature dependence of chemisorbed carbon critical cover Neq = Neq(T) has been measured, that is the cover when 2D phase transition takes place and graphene islands start to grow. E.g., Neq = 7.7•1014 cm-2 at T = 1800 K, and Neq = 3.1•1014 cm-2 at T = 1000 K.

Effect of Molecular Weight, Shape of the Molecule, and Presence of Polar Groups on the Autohesion of High Polymers. III

1957 ◽  
Vol 30 (2) ◽  
pp. 548-554 ◽  
Author(s):  
S. S. Voyutskiĭ ◽  
B. V. Shtarkh
Keyword(s):  
Activation Energy ◽  
Molecular Weight ◽  
Temperature Dependence ◽  
Structural Changes ◽  
Chain Molecule ◽  
Complete Disappearance ◽  
Short Side ◽  
Polar Groups ◽  
Kinetics Of ◽  
High Polymers

Abstract 1. It is shown for polyisobutylenes of different molecular weight that increase in the size of the chain molecule retards autohesion, but increases the limiting value to which the work of autohesion tends with increasing contact time. 2. Investigation of the temperature dependence of autohesion of polyisobutylenes showed that the activation energy does not depend on the molecular weight of the polyisobutylene. 3. It is shown for polybutadienes with varying contents of 1,4- and 1,2-structures that autohesion decreases with increase in the number of short side groups in the molecule, which apparently hinder diffusion by purely steric causes. 4. Investigation of the temperature dependence of autohesion of butadienenitrile copolymers with different contents of acrylonitrile in the molecule showed that the activation energy of autohesion increases with increase of polar nitrile groups in the polymer. 5. It is shown for the vulcanization of natural rubber that the formation of a spatial structure results in complete disappearance of autohesion in high polymers. It is shown that the kinetics of changes of autohesion during vulcanization can effectively characterize the structural changes which take place in the polymer during the process.

The Temperature Dependence of the Atoms Co Diffusion Coefficient in Pt80Co20(111) Alloy

2007 ◽  
Vol 265 ◽  
pp. 19-23
Author(s):  
M. Vasylyev ◽  
Vitaliy A. Tinkov ◽  
Sergey I. Sidorenko ◽  
S.M. Voloshko
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Temperature Dependence ◽  
Surface Segregation ◽  
Surface Region ◽  
Near Surface ◽  
Kinetics Of

The method of Ionization Spectroscopy is used to study the thermo-induced kinetics of surface segregation of the Pt80Co20(111) alloy components. The temperature dependence of the Co diffusion coefficient in this alloy is determined. It is found that the value of the activation energy for the segregation of Co atoms in the near-surface region is close to the heat of sublimation of pure Co.

Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst

1982 ◽  
Vol 47 (7) ◽  
pp. 1780-1786 ◽  
Author(s):  
Rostislav Kudláček ◽  
Jan Lokoč
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Liquid Phase ◽  
Ionizing Radiation ◽  
Oxide Catalyst ◽  
Absorbed Dose ◽  
Hydrogenation Rate ◽  
Solution Composition ◽  
Mixed Catalyst ◽  
Kinetics Of

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.

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