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 Kinetic Studies of Fibrinogen in Pregnant Rabbits

1977 ◽  
Author(s):  
R.-M. Moeller ◽  
I. Mahn ◽  
G. Müller-Berqhaus
Keyword(s):  
Kinetic Studies ◽  
Distribution Volume ◽  
Fractional Catabolic Rate ◽  
Third Trimester ◽  
The Third ◽  
Quantitative Measurements ◽  
Catabolic Rate ◽  
Average Acceleration ◽  
The Mean ◽  
Kinetics Of

During gestation increased concentrations of fibrin (ogen)derivatives are observed indicative of intravascular action of thrombin. The aim of this study was to elucidate the kinetics of fibrinogen during gestation. The elimination of homologous 1-125-fibrinogen was studied in 14 pregnant rabbits during the first as well as during the third trimesters of gestation. Control studies were performed with 10 non-pregnant rabbits.The mean distribution volume of labeled fibrinogen did not significantly differ between pregnant and non-pregnant rabbits. During the third trimester pregnant rabbits demonstrated a pronounced shortening of T 1/2 of labeled fibrinogen from a mean of 55.3 hr during the first to a mean of 29.7 hr during the third trimester. The experiments showed a significant increase in the fractional catabolic rate from 45.0 to 69.9% per day in the course of gestation. The shortening of T 1/2 of labeled fibrinogen correlated to the number of fetusses per litter.This study indicates an average acceleration of the fibrinogen turnover during gestation of about 50%. These direct quantitative measurements demonstrate that fibrinogen catabolism is pronouncedly accelerated during pregnancy.

The kinetics of elementary reactions involving the oxides of sulphur II. Chemical reactions in the sulphur dioxide afterglow

1966 ◽  
Vol 295 (1443) ◽  
pp. 363-379 ◽  
Keyword(s):  
Excited States ◽  
Sulphur Dioxide ◽  
Kinetic Studies ◽  
Absolute Intensity ◽  
Third Order ◽  
Elementary Reactions ◽  
The Third ◽  
Dominant Process ◽  
Recombination Reactions ◽  
Kinetics Of

The main recombination reactions in the sulphur dioxide afterglow are shown to be O + SO 2 + M = SO 3 + M (1) and O + SO + M = SO 2 + M , (2) with rate constants of (4·7 ± 0·8) x 10 15 and (3·2 ± 0·4) x 10 17 cm 6 mole -2 s -1 respectively at 300°K for M = Ar. Reaction (2) is the dominant process removing sulphur monoxide (SO) which is otherwise remarkably unreactive. The absolute intensity of the sulphur dioxide afterglow is found to be I = 1·5 x 10 8 [O] [SO] cm 3 mole -1 s -1 for argon carriers at pressures between 0·25 an d 3·0 mmHg. The afterglow emission comes from three excited states of SO 2 . Spectroscopic and kinetic studies show that these are populated subsequent to or by the third order combination reaction (2). Excited SO 2 is removed mainly by electronic quenching.

scholarly journals THE STUDY OF ELECTRICALLY DISCHARGED O2 BY MEANS OF AN ISOTHERMAL CALORIMETRIC DETECTOR

1959 ◽  
Vol 37 (10) ◽  
pp. 1680-1689 ◽  
Author(s):  
L. Elias ◽  
E. A. Ogryzlo ◽  
H. I. Schiff
Keyword(s):  
Gas Phase ◽  
Molecular Oxygen ◽  
Surface Recombination ◽  
Negative Temperature ◽  
Recombination Coefficient ◽  
Third Order ◽  
Atom Concentration ◽  
Electrodeless Discharge ◽  
First Order ◽  
A Value

Molecular oxygen was subjected to an electrodeless discharge in the pressure range 0.1–3 mm Hg. The oxygen atom concentration was measured as a function of time in a flow system by means of a movable atom detector which consisted of a platinum wire coated with a suitable catalyst for atom recombination. The atom concentration was calculated from the heat liberated when the detector was operated under isothermal conditions. The surface recombination was found to be first order in the atom concentration. A value of 7.7 × 10−5 was obtained for the recombination coefficient (γ) on Pyrex. No temperature dependence for γ was observed. The gas phase recombination of oxygen atoms was found to be consistent with the mechanism[Formula: see text]The rate constant for the third-order reaction was found to have a value of 1.0 × 1014 cc2 mole−2 sec−1, and a small negative temperature dependence.Evidence was also obtained for the presence of considerable amounts of excited molecular oxygen in electrically activated O2.

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.

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.

Kinetics and Temperature Dependence of the Hydration of NO+ in the Gas Phase

1973 ◽  
Vol 51 (3) ◽  
pp. 456-461 ◽  
Author(s):  
Margaret A. French ◽  
L. P. Hills ◽  
P. Kebarle
Keyword(s):  
Temperature Dependence ◽  
Gas Phase ◽  
Rate Constants ◽  
Room Temperature ◽  
Transfer Reaction ◽  
Negative Temperature ◽  
Ion Source ◽  
Third Order ◽  
The Third ◽  
Kinetics Of

The kinetics of the atmospherically important hydration sequence: NO+(H2O)n−1 + H2O = NO+(H2O)n and the transfer reaction NO+(H2O)n + H2O = HNO2 + H+(H2O)n were examined in nitrogen containing small quantities of NO and H2O with a pulsed high pressure ion source mass spectrometer. The room temperature mechanism and rate constants were found to be in agreement with earlier work in other laboratories. The temperature dependence of the reaction was examined for the range 27–157 °C. The transfer reaction does not occur at higher temperatures so that the NO+ hydration equilibria for n = 1 and 2 could be measured leading to ΔH1,0 = 18.5 and ΔH2,1 = 16.1 kcal/mol. The third order forward clustering rate constants were found to have negative temperature coefficients.

scholarly journals Kinetic studies in the chemistry of rubber and related materials. I. The thermal oxidation of ethyl linoleate

1946 ◽  
Vol 186 (1005) ◽  
pp. 218-236 ◽  
Keyword(s):  
Thermal Decomposition ◽  
Reaction Mechanism ◽  
Thermal Oxidation ◽  
Molecular Oxygen ◽  
Kinetic Studies ◽  
Ethyl Linoleate ◽  
Chain Termination ◽  
Radical Chain ◽  
Kinetics Of ◽  
Sole Product

The kinetics of the initial stages of the thermal oxidation of ethyl linoleate (by molecular oxygen) have been investigated in the temperature range 35—75° C. From consideration of chemical and kinetic evidence the reaction mechanism has been established: oxidation chains are initiated by thermal decomposition of ethyl linoleate hydroperoxide (which in the early stages of oxidation is substantially the sole product). The chain propagation reactions are identified as R — + O 2 → R O 2 — and R O 2 — + R H → R OOH + R — (where R H represents ethyl linoleate). Chain termination occurs by mutual destruction of the radical chain carriers, R — and R O 2 — .

The rates of elementary processes in the chain reaction between hydrogen and oxygen III. Kinetics of the combination of hydrogen atoms with nitric oxide

1967 ◽  
Vol 297 (1451) ◽  
pp. 520-533 ◽  
Keyword(s):  
Ground State ◽  
Third Body ◽  
Kcal Mole ◽  
Hydrogen Atoms ◽  
Chain Reaction ◽  
Elementary Processes ◽  
The Third ◽  
Electronically Excited ◽  
Kinetics Of ◽  
Related Process

A detailed study of the kinetics of the raction H + NO + M = HNO + M + 49.9 kcal/mole (1) shows that all the third bodies examined except H 2 O give similar relative efficiencies for the formation of ground state ( 1 A ') and electronically excited ( 1 A ") HNO. The overall rate constants found at 293°K (in cm 6 mole -2 s -1 x 10 -16 ) are: Ar, 1.11 ± 0.15; H 2 , 2.07 ± 0.18; CO 2 , 2.26 ± 0.23; N 2 O, 2⋅45 ± 0⋅44; SF 6 , 3.96 ± 0.46; H 2 O, 6.8 ± 1.2. For the reaction D + NO + Ar = DNO + Ar a rate constant of (1.28 ± 0.21) x 10 16 cm 6 mole -2 s -1 was obtained. The relative third body efficiencies in reaction (1) were less similar to the closely related Process H + O 2 + M = HO 2 + M + 47.1 kcal/mole than to the reaction O + NO + M = NO 2 + M + 73.2 kcal/mole.

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