scholarly journals The catalytic isomerization of buten-1

1941 ◽  
Vol 178 (972) ◽  
pp. 106-117 ◽  
Keyword(s):  
Double Bond ◽  
Hydrogen Pressure ◽  
Square Root ◽  
Double Bond Migration ◽  
Rate Determining Step ◽  
Catalytic Isomerization ◽  
Rate Of Reaction ◽  
Hydrogenation Reactions ◽  
Kinetics Of ◽  
Catalytic Exchange

It has been shown that butene-1 undergoes isomerization to butene-2 on a nickel catalyst in the presence of hydrogen. B y using deuterium, this double-bond migration has been examined simultaneously with the exchange and hydrogenation reactions. The kinetics of double-bond migration and hydrogenation at 65° C were found to be identical, the rate of reaction in both cases being proportional to the square root of the butene pressure and to the square root of the hydrogen pressure. Energies of activation for the three reactions were measured over the temperature range 76-126° C and the following values found: Exchange 9.0 kcal. Hydrogenation 2.5 ,, Double-bond migration 5.9 ,, At the lowest temperatures, the rate of double-bond migration was about six times that of exchange. These facts are in agreement with the theory that the catalytic exchange between olefines and deuterium takes place through the formation of an associative complex. The rate-determining step in the double-bond migration is the second, fast step of the exchange reaction, viz.

The Oxidation of Tetrahydrofuran by Ruthenium Tetroxide

1972 ◽  
Vol 50 (19) ◽  
pp. 3129-3134 ◽  
Author(s):  
Donald G. Lee ◽  
Matthijs Van Den Engh
Keyword(s):  
Perchloric Acid ◽  
Activation Parameters ◽  
Isotopic Labeling ◽  
Acid Solutions ◽  
Ruthenium Tetroxide ◽  
Rate Determining Step ◽  
Rate Of Reaction ◽  
Hydride Abstraction ◽  
Aqueous Perchloric Acid ◽  
Kinetics Of

The kinetics of the oxidation of tetrahydrofuran by ruthenium tetroxide in aqueous perchloric acid solutions have been investigated. The rate of reaction is found to be directly dependent on the concentrations of oxidant and reductant, but inversely dependent on the acidity of the medium. A mechanism involving hydride abstraction in the rate determining step was found to be consistent with the evidence obtained from isotopic labeling and an analysis of the activation parameters (ΔH≠ = 14.0 kcal/mol, ΔS≠ = −18.4 e.u.) of the reaction. This conclusion is further substantiated by noting the similarity between the reactions of ruthenium tetroxide with alcohols and ethers.

Catalytic Hydrogenation with Amorphous and Crystalline Pd8 0Si2 0

1981 ◽  
Vol 8 ◽  
Author(s):  
Bill C. Giessen ◽  
Sabri S. Mahmoud ◽  
David A. Forsyth ◽  
Markus Hediger
Keyword(s):  
Double Bond ◽  
Catalytic Hydrogenation ◽  
Metallic Glasses ◽  
Hydrogen Deuterium Exchange ◽  
Reaction Conditions ◽  
Crystalline Phases ◽  
Hydrogenation Catalysts ◽  
Double Bond Migration ◽  
Hydrogenation Reactions ◽  
Hydrogen Deuterium

ABSTRACTSeveral metallic glasses in the form of ribbons were screened for activity as hydrogenation catalysts. Pd80Si20 and (Ni50Fe50)80B20 showed activity in reducing cyclohexene. Pd 80 Si20 was further examined for differences between the glassy and crystalline phases in the selectivity shown during hydrogenation reactions of n-hexenes, phenylethyne, α-pinene, and cyclododecene. No significant differences were found for catalytic selectivity in regard to cis-trans isomerization, double bond migration, and stereochemistry of addition under the reaction conditions used. Minor differences were observed in hydrogen-deuterium exchange.

scholarly journals Mechanism of Oxidation of (p-Substituted Phenylthio)acetic Acids withN-Bromophthalimide

2011 ◽  
Vol 8 (1) ◽  
pp. 1-8 ◽  
Author(s):  
N. M. I. Alhaji ◽  
A. M. Uduman Mohideen ◽  
K. Kalaimathi
Keyword(s):  
Reaction Rate ◽  
Reaction Medium ◽  
Solvent Mixture ◽  
Kinetics Of Oxidation ◽  
Rate Determining Step ◽  
Water Solvent ◽  
Rate Of Reaction ◽  
Species Effect ◽  
Kinetics Of ◽  
Acetic Acids

The kinetics of oxidation of (phenylthio)acetic acid (PTAA) byN-Bromophthalimide (NBP) in acetonitrile-water solvent mixture at 298 K in the presence of perchloric acid has been followed potentiometrically. The reaction is first-order each in NBP and PTAA and inverse fractional-order in H+. Also, it has been found that the reaction rate is not affected by changes in ionic strength of the reaction medium or by the addition of chemicals such as phthalimide, acrylonitrile and potassium bromide. However, an increase in the water content of the solvent mixture causes an increase in the rate of reaction. These observations have been well analyzed in favour of a SN2-type mechanism, involving NBP itself as the reactive species. Effect of substituents on the reaction rate has been analysed by employing various (p-sustituted phenylthio)acetic acids. The electron-releasing substituent in the phenyl ring of PTAA accelerates the reaction rate while the electron-withdrawing substituent retards the rate. The excellently linear Hammett plot yields a large negative ρ value, supporting the involvement a bromosulphonium ion intermediate in the rate-determining step.

The kinetics of the photo-oxidation of benzaldehyde

1953 ◽  
Vol 218 (1133) ◽  
pp. 175-189 ◽  
Keyword(s):  
Rate Constants ◽  
Peroxy Radical ◽  
Photochemical Oxidation ◽  
Square Root ◽  
Peroxy Radicals ◽  
Photo Oxidation ◽  
Rate Determining Step ◽  
Perbenzoic Acid ◽  
Kinetics Of ◽  
Overall Kinetics

The direct photochemical oxidation of liquid benzaldehyde in n -decane solution has been investigated at temperatures from 5 to 20° C, the primary product being perbenzoic acid. The overall kinetics of the reaction are simple, the rate being proportional to the first power of the concentration of the aldehyde and to the square root of the intensity of the absorbed light. The rate is independent of oxygen pressure. These kinetics indicate that the dehydrogenation of the aldehyde by the peroxy radical is the rate-determining step in propagation. The termination step involves the interaction of two peroxy radicals. By means of the retardation and sector techniques the rate of initiation of the oxidation and the values of the rate constants have been determined.

Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

scholarly journals Single entity electrochemistry and the electron transfer kinetics of hydrazine oxidation

Nano Research ◽  
2021 ◽  
Author(s):  
Ruiyang Miao ◽  
Lidong Shao ◽  
Richard G. Compton
Keyword(s):  
Electron Transfer ◽  
Bulk Solution ◽  
Relative Contribution ◽  
Rate Determining Step ◽  
Multistep Process ◽  
Ph Range ◽  
Electro Catalytic Oxidation ◽  
Single Particle Impact ◽  
The Impact ◽  
Kinetics Of

AbstractThe mechanism and kinetics of the electro-catalytic oxidation of hydrazine by graphene oxide platelets randomly decorated with palladium nanoparticles are deduced using single particle impact electrochemical measurements in buffered aqueous solutions across the pH range 2–11. Both hydrazine, N2H4, and protonated hydrazine N2H5+ are shown to be electroactive following Butler-Volmer kinetics, of which the relative contribution is strongly pH-dependent. The negligible interconversion between N2H4 and N2H5+ due to the sufficiently short timescale of the impact voltammetry, allows the analysis of the two electron transfer rates from impact signals thus reflecting the composition of the bulk solution at the pH in question. In this way the rate determining step in the oxidation of each specie is deduced to be a one electron step in which no protons are released and so likely corresponds to the initial formation of a very short-lived radical cation either in solution or adsorbed on the platelet. Overall the work establishes a generic method for the elucidation of the rate determining electron transfer in a multistep process free from any complexity imposed by preceding or following chemical reactions which occur on the timescale of conventional voltammetry.

THE ALKALINE CLEAVAGE OF o-NITROBENZYLTRIMETHYLSILANE SOLVENT EFFECTS IN THE DIOXANE–WATER SYSTEM

1963 ◽  
Vol 41 (6) ◽  
pp. 1525-1530 ◽  
Author(s):  
H. R. Allcock
Keyword(s):  
Transition State ◽  
Solvent Effects ◽  
Water System ◽  
Solvent Polarity ◽  
High Water ◽  
Aqueous Dioxane ◽  
Alkaline Cleavage ◽  
Rate Of Reaction ◽  
Kinetics Of

The kinetics of alkaline cleavage of o-nitrobenzyltrimethylsilane were examined in aqueous dioxane media. At high water concentrations, increases in solvent polarity retard the cleavage, as required by a mechanism involving charge dispersion in the transition state. At high dioxane concentrations, solvent polarity increases are accompanied by increases in the rate of reaction, a result which may reflect association between the solvent components.

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