HOMOGENEOUS CATALYSIS OF D2–H2O EXCHANGE BY RUTHENIUM (III) CHLORIDE: EVIDENCE FOR THE HETEROLYTIC SPLITTING OF HYDROGEN

1966 ◽  
Vol 44 (6) ◽  
pp. 671-675 ◽  
Author(s):  
Jack Halpern ◽  
Brian R. James
Keyword(s):  
Exchange Rate ◽  
Exchange Reaction ◽  
Homogeneous Catalysis ◽  
Isotopic Exchange ◽  
Chloride Ion ◽  
Product Distribution ◽  
Hydrogen Ion ◽  
Rate Determining Step ◽  
Exchange Product ◽  
Catalyzed Oxidation

The prediction, based on earlier studies of the ruthenium(III) chloride catalyzed oxidation of H2 by iron(III), that in the absence of iron(III) or other oxidants ruthenium(III) chloride should catalyze homogeneously the isotopic exchange between D2 and H2O has been confirmed. A kinetic study was made of this exchange reaction in which the dependence of the exchange rate and of the exchange product distribution (HD:H2 ratio) on the concentrations of ruthenium(III), hydrogen ion, and chloride ion were determined. The results, and in particular the observation that the HD:H2 ratio of the exchange product increases with the concentrations cf H+ and Cl−, support the view that the ruthenium (III)-catalyzed oxidation of D2 by iron(III) and the D2–H2O exchange reaction proceed through related mechanisms involving a common rate-determining step in which D2 is split heterolytically and a deuteridoruthenium(III) complex is formed.

Homogeneous Catalysis of Hydrogen Isotope Exchange Between D2 and Ethanol by Chlorotris(triphenyIphosphine)rhodium(I). II. In Chloroform-Ethanol

1974 ◽  
Vol 52 (12) ◽  
pp. 2226-2235 ◽  
Author(s):  
Graeme Strathdee ◽  
Russell Given
Keyword(s):  
Activation Energy ◽  
Computer Simulation ◽  
Exchange Reaction ◽  
Homogeneous Catalysis ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Reaction Rate ◽  
Side Reaction ◽  
Rate Determining Step ◽  
Inverse Isotope Effect

The kinetics and mechanism of D2 exchange catalyzed by RhCl(PPh3)3 have been studied in chloroform–ethanol solutions. Interpretation of the results was complicated by a side reaction of the solvent to yield HCl, RhHCl2(PPh3)2, C2H5Cl, CH2Cl2, Ph3PO, and other phosphorus(V) species. Computer simulation of the exchange reaction was used to show that the observed inverse isotope effect [Formula: see text] could arise only if the rate determining step was the activation of D2, HD, and H2 by RhCl(PPh3)3.The D2 exchange reaction rate was extremely dependent on solvent composition and decreased 30 times between 6 and 96 mol% C2H5OH. The activation energy for D2 exchange was 101 ± 9 kJ mol−1 at 58 mol% C2H5OH, and 86 ± 8 kJ mol−1 at 6 mol% C2H5OH. These data suggested that solvent–catalyst bonding interactions were important.

Hydrogen isotopic exchange between D2 and H2O on alumina prepared by sputtering

1993 ◽  
Vol 71 (5) ◽  
pp. 663-669 ◽  
Author(s):  
Fumio Ioka ◽  
Tetsuo Sakka ◽  
Yukio Ogata ◽  
Matae Iwasaki
Keyword(s):  
Exchange Rate ◽  
Isotopic Exchange ◽  
Molecular Orbital Calculations ◽  
Base Pairs ◽  
Coordination Numbers ◽  
Rate Determining Step ◽  
Heat Treated ◽  
The Exchange Rate ◽  
Low Pressures ◽  
Oxygen Site

Hydrogen isotopic exchange between D2 and H2O has been investigated on alumina prepared by sputtering at 803 K and at low pressures. The alumina is amorphous, consisting of aluminum with coordination numbers four, five, and six in the ratio 1:2:1 as determined by NMR. A kinetic model is proposed on the basis of the pressure dependence of the exchange rate and the heats of adsorption at adsorbed sites, evaluating by molecular orbital calculations. The adsorbed sites are assumed to be Lewis acid–base pairs composed of a coordinatively unsaturated aluminum and the adjacent unsaturated oxygen site. The site relating to the rate-determining step contains threefold aluminum, which is formed by unsaturation of fourfold aluminum at the surface. As a consequence, the exchange rate depends on the amount of fourfold aluminum when the alumina is heat treated and changes its phase.

scholarly journals Catalytic Effect of Cetyltrimethylammonium Bromide on the Oxidation of Triethylene glycol by Chloramine-T in Acidic Medium

2008 ◽  
Vol 5 (4) ◽  
pp. 894-903 ◽  
Author(s):  
Vandana Sharma ◽  
K. V. Sharma ◽  
V. W. Bhagwat
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Reaction Rate ◽  
Catalytic Effect ◽  
Triethylene Glycol ◽  
Chloride Ion ◽  
Effect Of Temperature ◽  
Rate Determining Step ◽  
Excess Concentration ◽  
Chloramine T ◽  
Catalyzed Oxidation

The kinetics and mechanism of cetyltrimethylammonium bromide catalyzed oxidation of triethylene glycol [2,2'-ethylene diqxybis(ethanol)] by chloramine-T in acidic acid medium have been investigated. The reaction is first order dependence on chloramine-T and fractional order for triethylene glycol with excess concentration of other reactants. The catalytic effect due to cetyletrimethylammonium bromide has been studied. The small salt effect and increase in the reaction rate with increasing dielectric constant suggest the involvement of neutral molecule in the rate-determining step. The addition ofp-toluene sulfonamide retards the reaction rate. The effect of chloride ion on the reaction also studied. The effect of temperature on the reaction has been investigated in the temperature range 313-333K and thermodynamic parameters were calculated from the Arrhenious plot. A tentative mechanism consistent with the experimental results has been proposed.

scholarly journals Mixed Lithium and Sodium Ion Aprotic DMSO Electrolytes for Oxygen Reduction on Au and Pt Studied by DEMS and RRDE

2021 ◽  
Author(s):  
M. Hegemann ◽  
P. P. Bawol ◽  
A. Köllisch-Mirbach ◽  
H. Baltruschat
Keyword(s):  
Oxygen Reduction ◽  
Product Distribution ◽  
Reduction Reaction ◽  
Mixed Electrolytes ◽  
Peroxide Formation ◽  
Pt Electrode ◽  
Rate Determining Step ◽  
Differential Electrochemical Mass Spectrometry ◽  
Redox Couples ◽  
Pt Electrodes

AbstractIn order to advance the development of metal-air batteries and solve possible problems, it is necessary to gain a fundamental understanding of the underlying reaction mechanisms. In this study we investigate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER, from species formed during ORR) in Na+ containing dimethyl sulfoxide (DMSO) on poly and single crystalline Pt and Au electrodes. Using a rotating ring disk electrode (RRDE) generator collector setup and additional differential electrochemical mass spectrometry (DEMS), we investigate the ORR mechanism and product distribution. We found that the formation of adsorbed Na2O2, which inhibits further oxygen reduction, is kinetically favored on Pt overadsorption on Au. Peroxide formation occurs to a smaller extent on the single crystal electrodes of Pt than on the polycrystalline surface. Utilizing two different approaches, we were able to calculate the heterogeneous rate constants of the O2/O2− redox couple on Pt and Au and found a higher rate for Pt electrodes compared to Au. We will show that on both electrodes the first electron transfer (formation of superoxide) is the rate-determining step in the reaction mechanism. Small amounts of added Li+ in the electrolyte reduce the reversibility of the O2/O2− redox couples due to faster and more efficient blocking of the electrode by peroxide. Another effect is the positive potential shift of the peroxide formation on both electrodes. The reaction rate of the peroxide formation on the Au electrode increases when increasing the Li+ content in the electrolyte, whereas it remains unaffected on the Pt electrode. However, we can show that the mixed electrolytes promote the activity of peroxide oxidation on the Pt electrode compared to a pure Li+ electrolyte. Overall, we found that the addition of Li+ leads to a Li+-dominated mechanism (ORR onset and product distribution) as soon as the Li+ concentration exceeds the oxygen concentration. Graphical abstract

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