THE SILVER CATALYZED OXIDATION OF ETHYLENE: III. KINETICS OF ETHYLENE OXIDE OXIDATION

1954 ◽  
Vol 32 (4) ◽  
pp. 432-442 ◽  
Author(s):  
A. Orzechowski ◽  
K. E. MacCormack
Keyword(s):  
Ethylene Oxide ◽  
Initial Rate ◽  
Oxidation Mechanism ◽  
Kinetic Studies ◽  
Main Step ◽  
Direct Oxidation ◽  
Flow Rates ◽  
Rate Determining Step ◽  
Kinetics Of ◽  
Catalyzed Oxidation

A flow type apparatus was used for kinetic studies of the silver catalyzed oxidation of ethylene oxide (EtO) by oxygen at 274 °C. Using N2 as diluent the concentrations of O2 and ethylene oxide were varied independently from 9.9 to 79% and 2.35 to 9.4% respectively while a total pressure of 1 atmosphere was maintained. Flow rates were varied to give a range of contact times varying from 0.06 to 0.25 sec. It was shown that EtO is oxidized without previous dissociation into C2H4 and O2. The dependence of the initial rate of oxidation of EtO on reactant concentrations excludes isomerization of EtO (to acetalde hyde) as a main step in its oxidation, and a direct oxidation mechanism is suggested. The results of a few experiments to determine the extent of isomerization of EtO to acetaldehyde in the absence of oxygen are presented. No steady state could be achieved but the results may be used semiquantitatively to support the belief that isomerization is not the rate determining step in the oxidation of ethylene oxide.

THE ROLE OF REACTION PRODUCTS IN THE SILVER-CATALYZED OXIDATION OF ETHYLENE

1960 ◽  
Vol 38 (11) ◽  
pp. 2256-2268 ◽  
Author(s):  
Kenneth E. Hayes
Keyword(s):  
Carbon Dioxide ◽  
Ethylene Oxide ◽  
Initial Rate ◽  
Flow System ◽  
Oxygen Exchange ◽  
Reaction Products ◽  
Exchange Reactions ◽  
Kinetics Of ◽  
Catalyzed Oxidation

Initial-rate studies of the kinetics of the silver-catalyzed oxidation of ethylene oxide and carbon dioxide in a flow system have been made. It was found that, using carefully purified reactants, the effect of added carbon dioxide was to suppress the formation of ethylene oxide only. The initial rate of the formation of ethylene oxide is given by the equation[Formula: see text]where r0 is the initial rate in the absence of CO2; m, n, and k are constants with m + n = 1.These results together with the results of oxygen exchange reactions between O18 and C2H4O16, CO216 and H2O16 are interpreted mechanistically.

KINETIC STUDIES OF METHYL-BIS-β-CHLOROETHYLAMINE: III. THE KINETICS OF THE DIMERIZATION IN METHANOL

1948 ◽  
Vol 26b (2) ◽  
pp. 175-180 ◽  
Author(s):  
C. A. Winkler ◽  
A. W. Hay ◽  
A. L. Thompson
Keyword(s):  
Rate Constants ◽  
Initial Rate ◽  
Kinetic Studies ◽  
First Order ◽  
Rate Expression ◽  
Principal Reaction ◽  
Kinetics Of ◽  
Rate Controlling Step

The principal reaction of methyl-bis-β-chloroethylamine in methanol is dimerization, which results in one chlorine from each molecule becoming ionic, but this is accompanied by slight alcoholysis. The rate-controlling step is believed to be the first order formation of an ethylenimonium ion which reacts rapidly with one of its kind to form dimer. The rate expression as calculated from initial rate constants is k (initial) = 4.0 × 1013e−19600/RThr.−1.

Succinyl Coenzyme A Synthetase of Escherichia coli: Initial Rate Kinetics of Succinyl-CoA Cleavage and Isotope Exchange Studies

1973 ◽  
Vol 51 (1) ◽  
pp. 44-55 ◽  
Author(s):  
Frank J. Moffet ◽  
W. A. Bridger
Keyword(s):  
Isotope Exchange ◽  
Coenzyme A ◽  
Initial Rate ◽  
Substrate Inhibition ◽  
Kinetic Studies ◽  
Kinetic Mechanism ◽  
Constant Ratio ◽  
Rate Kinetics ◽  
Kinetics Of ◽  
Succinyl Coenzyme A Synthetase

Initial rate kinetic studies of succinyl coenzyme A synthetase of E. coli in the direction of succinyl-CoA cleavage are consistent with the operation of a partially random sequential kinetic mechanism with initial binding of ADP followed by random association of succinyl-CoA and Pi. The mechanism is analogous to that proposed previously for the succinyl-CoA formation reaction, and thus the kinetic mechanism of the overall reversible succinyl-CoA synthetase reaction appears to be symmetrical.Studies of the kinetics of [Formula: see text] isotope exchange at equilibrium show that this partially random sequential kinetic mechanism is not an exclusive pathway. [Formula: see text] isotope exchange rates did not show complete substrate inhibition when CoA or succinate was varied in constant ratio with Pi. However, when CoA or succinate was varied in constant ratio with succinyl-CoA, nearly complete substrate inhibition was observed. These results can be interpreted in terms of a wide variety of minor pathways of substrate binding and product release available to the enzyme under various conditions.

Rates of elementary processes in the chain reaction between hydrogen and oxygen II. Kinetics of the reaction of hydrogen atoms with molecular oxygen

1963 ◽  
Vol 275 (1363) ◽  
pp. 559-574 ◽  
Keyword(s):  
Molecular Oxygen ◽  
Kinetic Studies ◽  
Negative Temperature ◽  
Product Analysis ◽  
Hydrogen Atoms ◽  
The Third ◽  
Rate Determining Step ◽  
A Value ◽  
Explosion Limit ◽  
Kinetics Of

The addition of molecular oxygen was found to increase the rate of rem oval of hydrogen atoms in a flow system at and below room temperature. Kinetic studies of this process using argon carrier showed that the rate-determining step is the third-order reaction H + O2 + Ar = HO 2 + Ar. (2) Atomic oxygen in small concentrations is produced in the system. Product analysis and measurements of oxygen atom concentrations indicated that the principal reactions removing HO 2 under these conditions are H+HO 2 = H 2 +O 2 , (12a) H+HO 2 = OH+OH, (12b) H+HO 2 = H 2 O+O 2 , (12c) A value for k 2 of 2.2 x 10 -32 cm 6 molecule -2 s -1 was determined at 293 °K. Reaction (2) was found to have a small negative temperature coefficient. These data and values of k 2 from explosion limit studies can be represented by the expression k 2 = 1.3 x 10 -33 exp (+ 1600 + 700/ RT ) cm 6 molecule -2 s -1 in the range 250 to 800 °K. The third-body efficiencies in reaction (2) at 293 °K of He and H 2 O relative to Ar are similar to those obtained from data on the second explosion limit at higher temperatures.

scholarly journals The mechanism of the catalytic oxidation of ethylene - I. Experiments using a flow system

1946 ◽  
Vol 188 (1012) ◽  
pp. 92-104 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Ethylene Oxide ◽  
Catalytic Oxidation ◽  
Flow System ◽  
Oxidation Reactions ◽  
Direct Oxidation ◽  
Rate Of Reaction ◽  
Reaction Proceeds ◽  
Products Of Reaction ◽  
Kinetics Of

Experiments have been made using a flow system to determine the mechanism of the catalytic oxidation of ethylene on a silver catalyst. The effects of time of contact of the gases with the catalyst, gas concentration, and temperature have been investigated. The products of reaction are ethylene oxide, and carbon dioxide and water. There appear to be two processes whereby the carbon dioxide is formed: (1) by direct oxidation of the ethylene not via ethylene oxide, and (2) by the further oxidation of the ethylene oxide. The isomerization of ethylene oxide to acetaldehyde by the catalyst in the absence of any oxygen has also been examined. By comparison with the oxidation of ethylene oxide, it has been shown that this latter reaction proceeds to a large extent, and possibly entirely, through a preliminary isomerization of the ethylene oxide to acetaldehyde. The rate of oxidation of acetaldehyde is extremely rapid and no trace of acetaldehyde is found during the oxidation of ethylene or of ethylene oxide. Ethylene oxide forms on the catalyst an involatile deposit, which is oxidized away by oxygen, so that during oxidation reactions the quantity of it on the catalyst is kept low. The kinetics of the oxidation of ethylene, i.e. rate of reaction proportional to the oxygen concentration and slightly dependent on the ethylene pressure, are consistent with the view that ethylene reacts with oxygen adsorbed on the catalyst and that the slowest step in the whole series of reactions is the rate of adsorption of the oxygen. An energy of activation of about 27 kcal. was found for the production of ethylene oxide, and slightly less for the production of carbon dioxide and consumption of oxygen.

Kinetic studies on carbohydrates in alkaline conditions. - I. The kinetics of the autoxidation of glucose

1950 ◽  
Vol 204 (1076) ◽  
pp. 62-84 ◽  
Keyword(s):  
Steady State ◽  
Alkaline Solution ◽  
Kinetic Studies ◽  
High Oxygen ◽  
Absolute Velocity ◽  
Rate Determining Step ◽  
Ionic Intermediates ◽  
Alkaline Conditions ◽  
Autoxidation Reaction ◽  
Kinetics Of

The autoxidation of glucose and fructose in alkaline solution has been shown to result in the almost quantitative formation of formic and arabonic acids at high oxygen pressures. Under these conditions, the degradation and interconversion reactions are suppressed and the autoxidation reaction reaches a limiting rate. From a general kinetic examination of the autoxidation reaction, evidence is obtained in support of the idea that, at high oxygen pressures, the rate-determining step is that of the parallel formation of two ionic intermediates. The kinetics of the autoxidation can be completely explained in terms of simple reactions of these intermediates. The absolute velocity constants for the formation of the intermediates have been determined from steady-state experiments. Experiments in the non-steady state have enabled the calculation of the concentrations of the intermediates to be made, and thus the velocity constants for their reaction with oxygen can be estimated.

THE SILVER CATALYZED OXIDATION OF ETHYLENE: II. KINETICS OF C2H4 OXIDATION

1954 ◽  
Vol 32 (4) ◽  
pp. 415-431 ◽  
Author(s):  
A. Orzechowski ◽  
K. E. MacCormack
Keyword(s):  
Total Pressure ◽  
Present Series ◽  
Initial Reaction ◽  
Flow Rates ◽  
Flow Type ◽  
Partial Pressures ◽  
C2h4 Oxidation ◽  
Kinetics Of ◽  
Catalyzed Oxidation ◽  
Type Apparatus

A flow-type apparatus is described and results given for the investigation of the kinetics of the silver catalyzed oxidation of C2H4 by oxygen. Using N2 as diluent, the concentrations of both O2 and C2H4 were varied independently from 9.9 to 79.0% and 2.35 to 9.40% respectively, whilst maintaining a total pressure of 1 atmosphere. Flow rates were varied to give a range of contact times varying from 0.05 to 1 sec. Measurements were made at 234 °C and 274 °C and the data used to estimate initial reaction velocities for both EtO and CO2 formation as a function of O2 and C2H4 partial pressures. These rates were fitted successfully to equations deduced theoretically in Part IV of the present series.

scholarly journals Kinetic studies of the mechanism of pig kidney aldehyde reductase

1981 ◽  
Vol 193 (2) ◽  
pp. 485-492 ◽  
Author(s):  
F F Morpeth ◽  
F M Dickinson
Keyword(s):  
Initial Rate ◽  
Kinetic Studies ◽  
Random Order ◽  
Alcohol Oxidation ◽  
Aldehyde Reductase ◽  
Pig Kidney ◽  
Binary Complexes ◽  
Inhibition Studies ◽  
Kinetics Of ◽  
Aldehyde Reduction

Initial-rate measurements were made of the oxidations of pyridine-3-methanol and glycerol by NADP+ and of the reduction of the corresponding aldehydes by NADPH catalysed by pig kidney aldehyde reductase. In addition, a brief survey of the specificity of the enzyme towards aldehyde substrates and its sensitivity to the inhibitors ethacrynic acid, sodium barbitone and warfarin was made. The detailed kinetic work indicates a compulsory mechanism for aldehyde reduction, with NADPH binding before aldehyde. For alcohol oxidation, however, it is necessary to postulate the formation of kinetically significant amounts of binary complexes of the type enzyme-alcohol to explain the results. Thus, for alcohol oxidation random-order addition of substrates may occur. Inhibition studies of the kinetics of aldehyde reduction in the presence of the corresponding alcohol product provide further evidence for the existence of enzyme-alcohol complexes. Finally, detailed kinetic studies were made of the inhibition of pyridine-3-aldehyde reduction by sodium barbitone. The mechanism of the inhibition is discussed.

scholarly journals Kinetic studies on the reaction catalysed by phosphofructokinase from Trypanosoma brucei

1987 ◽  
Vol 245 (1) ◽  
pp. 13-18 ◽  
Author(s):  
C N Cronin ◽  
K F Tipton
Keyword(s):  
Trypanosoma Brucei ◽  
Initial Rate ◽  
Reaction Pathway ◽  
Potassium Phosphate ◽  
Kinetic Studies ◽  
Enzyme Concentration ◽  
Product Inhibition ◽  
Steady State Kinetics ◽  
Fructose 1,6 Bisphosphate ◽  
Kinetics Of

The steady-state kinetics of the reaction catalysed by the bloodstream form of Trypanosoma brucei were studied at pH 6.7. In the presence of 50 mM-potassium phosphate buffer, the apparent co-operativity with respect to fructose 6-phosphate and the non-linear relationship between initial velocity and enzyme concentration, which were found when the enzyme was assayed in 50 mM-imidazole buffer [Cronin & Tipton (1985) Biochem. J. 227, 113-124], are not evident. Studies on the variations of the initial rate with changing concentrations of MgATP and fructose 6-phosphate, the product inhibition by fructose 1,6-bisphosphate and the effects of the alternative substrate ITP were consistent with an ordered reaction pathway, in which MgATP binds to the enzyme before fructose 6-phosphate, and fructose 1,6-bisphosphate is the first product to dissociate from the ternary complex.

KINETIC STUDIES ON METHYL-BIS-β-CHLOROETHYLAMINE: II. THE KINETICS OF THE ACTION OF SODIUM THIOSULPHATE ON THE PIPERAZINIUM DIMER

1948 ◽  
Vol 26b (2) ◽  
pp. 170-174
Author(s):  
C. A. Winkler ◽  
A. L. Thompson ◽  
T. J. Hardwick
Keyword(s):  
Rate Constants ◽  
Initial Rate ◽  
Kinetic Studies ◽  
Ionization Mechanism ◽  
Sodium Thiosulphate ◽  
First Order ◽  
Rate Expression ◽  
Order Rate ◽  
Kinetics Of ◽  
Rate Controlling Step

It has been shown analytically that for this reaction the formation of Cl− agrees with S2O3− disappearance. The approximate first order rate-controlling step is postulated to be dependent on an ionization mechanism. The rate expression calculated from initial rate constants is given approximately by k = 4.0 × 1015e−25,500/RT hr.−1.

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