Reaction of 1,3-diphenyltriazene with phenyl isocyanate. Solvent effect, activation parameters and kinetic isotopic effect

1981 ◽  
Vol 46 (6) ◽  
pp. 1376-1382
Author(s):  
Erhard Lejdar ◽  
Oldřich Pytela ◽  
Miroslav Večeřa ◽  
Pavel Vetešník
Keyword(s):  
Hydrogen Atom ◽  
Solvent Effect ◽  
Temperature Dependence ◽  
Activation Parameters ◽  
Phenyl Isocyanate ◽  
Isotopic Effect ◽  
Imino Group ◽  
Reaction Velocity ◽  
Kinetic Isotopic Effect ◽  
Previous Communication

Effect of 14 solvents has been studied on the reaction of phenyl isocyanate with 1,3-diphenyltriazene. For ten of these solvents temperature dependence of the reaction velocity has been determined and the respective activation parameters calculated. Hydrogen atom of the triazene imino group has been replaced by deuterium, and the deuterium kinetic isotopic effect has been studied in seven solvents. The results confirm the mechanism suggested in a previous communication.

Cyclization of O-benzoylbenzamidoxime derivatives in water-alcohol media

1985 ◽  
Vol 50 (12) ◽  
pp. 2722-2729 ◽  
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Mechanism ◽  
Electron Acceptor ◽  
Activation Parameters ◽  
Isotopic Effect ◽  
Hammett Equation ◽  
Probability Level ◽  
Kinetic Isotopic Effect ◽  
Cyclization Rate ◽  
Two Parameter ◽  
Water Alcohol

O-Benzoylated benzamidoximes give 1,2,4-oxadiazoles (yields above 90%) in water-alcoholic media of pH = 2.45 to 6.20. The cyclization rate has been studied with 28 derivatives containing different substituents. The reaction is accelerated by electron-donor substituents at 4-position of benzamidoxime and by electron-acceptor substituents at 4'-position of benzoyl. The dependence of the rate constants vs σ values of the substituents fulfils the two-parameter Hammett equation at a 99% probability level. The activation parameters have been determined, and effects of polarity of medium, kinetic isotopic effect, and the reaction mechanism are discussed.

Temperature dependence of the kinetic isotopic effect of the reaction of Cl atoms with C2H5Cl between 298 and 550K

2012 ◽  
Vol 554 ◽  
pp. 20-26 ◽  
Author(s):  
Dariusz Sarzyński ◽  
Agnieszka A. Gola ◽  
Katarzyna Brudnik ◽  
Ryszard Berkowski ◽  
Jerzy T. Jodkowski
Keyword(s):  
Temperature Dependence ◽  
Isotopic Effect ◽  
Kinetic Isotopic Effect ◽  
Cl Atoms

Radiolysis studies on the corrosion inhibitors 1 -hexyn-3-ol, cinnamonitrile, and 1,3-diethyl-2-thiourea

1995 ◽  
Vol 73 (12) ◽  
pp. 2137-2142 ◽  
Author(s):  
A.J. Elliot ◽  
M.P. Chenier ◽  
D.C. Ouellette
Keyword(s):  
Hydrogen Atom ◽  
Hydroxyl Radical ◽  
Temperature Dependence ◽  
Rate Constant ◽  
Rate Constants ◽  
Corrosion Inhibitors ◽  
Hydrated Electron

In this publication we report: (i) the rate constants for reaction of the hydrated electron with 1-hexyn-3-ol ((8.6 ± 0.3) × 108 dm3 mol−1 s−1 at 18 °C), cinnamonitrile ((2.3 ± 0.2) × 1010 dm3 mol−1 s−1 at 20 °C), and 1,3-diethyl-2-thiourea ((3.5 ± 0.3) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile and diethylthiourea, the temperature dependence up to 200 °C and 150 °C, respectively, is also reported; (ii) the rate constants for the reaction of the hydroxyl radical with 1-hexyn-3-ol ((5.5 ± 0.5) × 109 dm3 mol−1 s−1 at 20 °C), cinnamonitrile ((9.2 ± 0.3) × 109 dm3 mol−1 s−1 at 21 °C), and diethylthiourea ((8.0 ± 0.8) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile, the temperature dependence up to 200 °C is also reported; (iii) the rate constant for the hydrogen atom reacting with 1-hexyn-3-ol ((4.3 ± 0.4) × 109 dm3 mol−1 s−1 at 20 °C). Keywords: radiolysis, corrosion inhibitors, rate constants.

scholarly journals The role of enzyme dynamics and tunnelling in catalysing hydride transfer: studies of distal mutants of dihydrofolate reductase

2006 ◽  
Vol 361 (1472) ◽  
pp. 1307-1315 ◽  
Author(s):  
Lin Wang ◽  
Nina M Goodey ◽  
Stephen J Benkovic ◽  
Amnon Kohen
Keyword(s):  
Temperature Dependence ◽  
Dihydrofolate Reductase ◽  
Isotope Effects ◽  
Hydride Transfer ◽  
Activation Parameters ◽  
Physical Nature ◽  
Enzyme Dynamics ◽  
Temperature Dependences ◽  
Donor Acceptor ◽  
Significant Temperature

Residues M42 and G121 of Escherichia coli dihydrofolate reductase ( ec DHFR) are on opposite sides of the catalytic centre (15 and 19 Å away from it, respectively). Theoretical studies have suggested that these distal residues might be part of a dynamics network coupled to the reaction catalysed at the active site. The ec DHFR mutant G121V has been extensively studied and appeared to have a significant effect on rate, but only a mild effect on the nature of H-transfer. The present work examines the effect of M42W on the physical nature of the catalysed hydride transfer step. Intrinsic kinetic isotope effects (KIEs), their temperature dependence and activation parameters were studied. The findings presented here are in accordance with the environmentally coupled hydrogen tunnelling. In contrast to the wild-type (WT), fluctuations of the donor–acceptor distance were required, leading to a significant temperature dependence of KIEs and deflated intercepts. A comparison of M42W and G121V to the WT enzyme revealed that the reduced rates, the inflated primary KIEs and their temperature dependences resulted from an imperfect potential surface pre-arrangement relative to the WT enzyme. Apparently, the coupling of the enzyme's dynamics to the reaction coordinate was altered by the mutation, supporting the models in which dynamics of the whole protein is coupled to its catalysed chemistry.

Kinetic Isotopic Effect Studies of Iron–Nitrogen–Carbon Electrocatalysts for Oxygen Reduction Reaction

2019 ◽  
Vol 123 (18) ◽  
pp. 11476-11483 ◽  
Author(s):  
Yechuan Chen ◽  
Tristan Asset ◽  
Rose Lee ◽  
Kateryna Artyushkova ◽  
Plamen Atanassov
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Reduction Reaction ◽  
Isotopic Effect ◽  
Kinetic Isotopic Effect
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