Die Kinetik und der Mechanismus der thermischen Reaktion zwischen Schwefeltetrafluorid und Fluor / The Kinetics and the Mechanism of the Thermal Reaction between Sulfurtetrafluoride and Fluorine

1981 ◽  
Vol 36 (11) ◽  
pp. 1381-1385 ◽  
Author(s):  
Alicia Cristina Gonzalez ◽  
Hans Joachim Schumacher
Keyword(s):  
Chain Length ◽  
Total Pressure ◽  
Reaction Rate ◽  
Thermal Reaction ◽  
Primary Process ◽  
Chain Reaction ◽  
Experimental Conditions ◽  
Medium Length ◽  
A Chain ◽  
Kinetics Of

AbstractThe kinetics of the thermal reaction between SF4 and F2 has been investigated between − 2.4 °C and + 24.0 °C, SF6 and very small amounts of S2F10 being the only products. The reaction is a chain reaction of medium length. Total pressure and surface have only insignificant influence. The reaction rate follows the equation: Under the experimental conditions less than 15% of the SF5 radicals are consumed by r (4b). Therefore Oxygen inhibits the reaction eliminating the SF5 radicals, the final products being now SF5O3SF5 and SF6. From the data obtained in the experiments with high oxygen pressures the rate constant of the primary process and the chain length (v) are determined. E = 10.8 ± 0.7 kcal, E1 = 11.9 ± 0.6 kcal and E4 ≃ 0. E2 = 5.0 ± 2.0 kcal (estimated value) and E3 = 4.7 ± 2.5 kcal.

scholarly journals A study of the chain reaction in the thermal decomposition of diethyl ether.

1938 ◽  
Vol 167 (931) ◽  
pp. 456-463 ◽  
Author(s):  
J. E. Hobbs ◽  
Cyril Norman Hinshelwood
Keyword(s):  
Thermal Decomposition ◽  
Diethyl Ether ◽  
Reaction Rate ◽  
Initial Rate ◽  
Intramolecular Rearrangement ◽  
Chain Mechanism ◽  
Chain Reaction ◽  
Experimental Conditions ◽  
Rearrangement Process ◽  
A Chain

In a recent paper (Hobbs and Hinshelwood 1938), information about the chain mechanisms involved in the thermal decomposition of ethane was obtained by studying the variation with the ethane concentration of the shape of the curve which represents in the reaction rate as a function of minute quantities of added nitric oxide. This paper describes the results of a similar investigation carried out with diethyl ether, the behaviour of which shows an interesting contrast with that of ethane. The thermal decomposition of diethyl ether in the neighbourhood of 500° C. occurs partly by a chain mechanism in which free radicals are formed, and partly by intramolecular rearrangement (Staveley and Hinshelwood 1936, 1937). The end- products of the decomposition are methane, ethane, and carbon monoxide, with small amounts of hydrogen and unsaturated substances. Acetaldehyde is an intermediate product formed either in the rearrangement process, or, as in the mechanism put formed below, during the chain reaction (Fletcher and Rollefson 1936). The acetaldehyde, however, decomposes rapidly under the experimental conditions and the initial rate is sensibly that of the decomposition of the ether into final products.

The theory of flame phenomena with a chain reaction

1956 ◽  
Vol 249 (957) ◽  
pp. 1-25 ◽  
Keyword(s):  
Reaction Zone ◽  
Flame Propagation ◽  
Reaction Rate ◽  
Laminar Flame ◽  
Combustible Mixture ◽  
Flame Speed ◽  
Spontaneous Ignition ◽  
Chain Reaction ◽  
Hydrazine Decomposition ◽  
A Chain

For single-step reactions there is a unique relation between reaction rate and reactedness for a given combustible mixture at a specified pressure and initial temperature. This paper examines whether the relation is still unique when chain reactions are present, by considering three types of flame—spontaneous ignition, laminar-flame propagation, and the homogeneous steady-flow reaction zone—with a chain-reaction scheme proposed by Adams & Stocks for the decomposition of hydrazine. It is found that the relation is not unique but that similarities exist between the relation for laminar-flame propagation and the relation for the homogeneous reaction zone. Incidentally, a general method of calculating laminar-flame speeds with reaction schemes of arbitrary complexity is presented. When applied to the hydrazine decomposition flame the predictions of the theory are in fair agreement with experimental results. In particular, the variation of flame speed with temperature is correctly predicted. It is shown that the use of the Karman-Penner 'steady-state assumption' would lead to an overestimate of the flame speed. Consideration of the changes which would result if the chain reaction should branch shows that there would once again tend to be a unique reaction rate versus reactedness relation, and that the laminar-flame speed would be increased by a factor of about three for the hottest flame considered but by larger factors for cooler flames.

scholarly journals Purification, properties and cellular localization of the stereospecific CS2 secondary alkylsulphohydrolase of Comamonas terrigena

1977 ◽  
Vol 167 (3) ◽  
pp. 723-729 ◽  
Author(s):  
G W J Matcham ◽  
K S Dodgson ◽  
J W Fitzgerald
Keyword(s):  
Chain Length ◽  
Cellular Localization ◽  
Indirect Evidence ◽  
Initial Study ◽  
Potassium Salts ◽  
Experimental Conditions ◽  
Alkyl Sulphate ◽  
A Subunit ◽  
A Chain ◽  
Comamonas Terrigena

The availability of homogeneous samples of the potassium salts of L- and D-octan-2-yl sulphate has enabled the separation of the optically stereospecific CS1 and CS2 secondary alkysulphohydrolases from extracts of cells of Comamonas terrigena. The CS2 enzyme was purified to homogeneity, and an initial study was made of its general properties, specificity, cellular localization and relationship to the CS1 enzyme. The CS2 enzyme has a molecular weight of approx. 250000 and a subunit size of approx. 58000, indicating that the molecule is a tetramer. Under the experimental conditions used the enzyme appears to be specific for (+)-secondary alkyl sulphate esters with the sulphate group at C-2 and with a chain length of at least six carbons. Enzyme activity towards racemic C-2 sulphates increases with increasing chain length up to C10, and there is some indirect evidence to suggest that activity declines when that chain length is exceeded. Other indirect evidence confirms that the CS1 enzyme exhibits similar specificity, except that only (-)-isomers can serve as substrates. Both enzymes are present in broth-grown stationary-phase cells of C. terrigena in approximately equal amounts.

scholarly journals Carbon Dioxide Gasification Kinetics of Char from Rapeseed Oil Press Cake

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2318 ◽  
Author(s):  
Lech Nowicki ◽  
Dorota Siuta ◽  
Maciej Markowski
Keyword(s):  
Carbon Dioxide ◽  
Rapeseed Oil ◽  
Reaction Rate ◽  
Press Cake ◽  
Agricultural Waste ◽  
Estimation Procedure ◽  
Experimental Conditions ◽  
Two Step Estimation ◽  
Kinetics Of ◽  
Carbon Dioxide Gasification

Rapeseed oil press cake (RPC) is an abundantly available and renewable agricultural waste material for the production of fuels or chemicals. In this study, the rates of carbon dioxide gasification of rapeseed oil press cake char were measured by thermogravimetric analysis measurements performed at various temperatures (800–900 °C) and CO2 mole fractions (0.10–1.00). The char was obtained by slow pyrolysis, where the dried RPC was decomposed at a temperature range of 1000 °C to obtain char free of impurities that can affect the measurements. The random pore model appeared to be suitable for describing the effect of conversion on the reaction rate. The temperature, CO2, and concentration dependence of the reaction rate were given by the Arrhenius equation and a power law (nth order) correlation. The kinetic parameters based on the experimental data were determined by a two-step estimation procedure. For the experimental conditions employed in this study, the parameters E and n were 222.1 kJ/mol and 0.57, respectively.

Kinetics of the reaction between Manganese Dioxide and Ferrous Ion

1957 ◽  
Vol 10 (2) ◽  
pp. 150 ◽  
Author(s):  
DFA Koch
Keyword(s):  
Manganese Dioxide ◽  
Surface Area ◽  
Active Sites ◽  
Reaction Rate ◽  
Ferrous Sulphate ◽  
Zero Order ◽  
Ferrous Ion ◽  
Active Surface Area ◽  
Experimental Conditions ◽  
Kinetics Of

The kinetics of the reaction between manganese dioxide and ferrous ion in acid solution have been investigated by using the potential of the ferrous-ferric couple as a measure of the extent of reaction. The experimental conditions were such that the reaction rate was independent of ferrous, ferric, manganous ions, and acid concentrations and the agitation was sufficient to prevent bulk diffusion in the solution from being a rate-determining factor. The reaction rate of sized samples of pyrolusite and γ-MnO2 in ferrous sulphate solution was proportional to the surface area of the solid and was constant (i.e. " zero-order ") until 50 per cent. of the solid was consumed. γ-MnO2 reacted about twice as rapidly as the pyrolusite. The reaction occurred most readily at certain active sites on the particles and appeared to proceed along crystal boundaries in such a manner that the active surface area was not significantly changed during the first half of the reaction. In ferrous perchlorate the reaction rate of 10 μ diameter pyrolusite was about one-hundredth of that in sulphate and the reaction appeared to occur at a more even rate over the whole surface of the particle so that the zero-order law was no longer obeyed. Activation energies of 7.4 and 5 kcal in sulphate and perchlorate respectively, for the temperature range 18 to 40 �C, suggest that the difference in rate is a result of a change in the entropy factor of the Arrhenius equation. It is suggested that this difference in rate may result from the activation, by sulphate ions, of a less reactive lower oxide of manganese which is formed on the surface.

Studies of Ozone Attack of Vulcanizates in a Closed System

1964 ◽  
Vol 37 (3) ◽  
pp. 583-605
Author(s):  
John C. McCool
Keyword(s):  
Closed System ◽  
Total Pressure ◽  
Surface Films ◽  
Chain Reaction ◽  
Environmental Conditioning ◽  
Definite Effect ◽  
Elastic Forces ◽  
Per Se ◽  
A Chain ◽  
Ozone Resistance

Abstract 1. A new procedure for studying the attack of vulcanizates by ozone in a closed system has been devised which permits measuremont of ozone consumption as a function of strain, environments, and compounding aspects. 2. Extent of attack is best determined by cut growth measurements and by photographic records of the samples after test. 3. The accelerated attack by ozone observed at reduced total pressure reported now as a new observation appears to reflect the probability of ozone collisions with olefinic bonds which are part of uncoiled or “strained” polymer segments. Retraction of the chain ends formed by cleavage due to elastic forces present determines the rate at which sub-surface networks become accessible to ozone. 4. Ozone consumption per se does not predict the resistance of a vulcanizate to ozone attack, nor does it correlate with the presence of antioxidants or antiozonants. 5. Environmental conditioning of vulcanizates has a definite effect on their ozone resistance, indicative of the role which surface films have on protection. 6. The effects of antiozonants appear to represent a protective principle involving their reaction with the ozone cleavage products of olefinic bonds. 7. No evidence has been found to indicate that ozone attack of vulcanizates proceeds through a chain reaction involving oxygen.

THE KINETICS OF THE THERMAL DECOMPOSITION OF DISULPHUR DECAFLUORIDE

1951 ◽  
Vol 29 (6) ◽  
pp. 508-525 ◽  
Author(s):  
W. R. Trost ◽  
R. L. McIntosh
Keyword(s):  
Nitric Oxide ◽  
Thermal Decomposition ◽  
Heterogeneous Reaction ◽  
Homogeneous Reaction ◽  
Chain Reaction ◽  
First Order ◽  
Reaction Proceeds ◽  
Total Process ◽  
A Chain ◽  
Kinetics Of

The thermal decomposition of the gas disulphur decafluoride has been studied in a metal reactor. Analytical evidence showed that the reaction proceeds according to the equation S2F10 = SF6 + SF4.The reaction was found to be largely homogeneous, as the heterogeneous reaction accounted for less than 5% of the total process. The homogeneous reaction was shown to be first order, and in the temperature range investigated the rate is given by ln k = 47.09 − 49,200/RT. A chain reaction is postulated to explain the observed rate of the reaction. The effect of nitric oxide and acetylene dichloride on the rate and products of the reaction was investigated.

scholarly journals Oxidation of some catecholamines by sodium N-chloro-p-toluenesulfonamide in acid medium: A kinetic and mechanistic approach

2005 ◽  
Vol 3 (2) ◽  
pp. 326-346 ◽  
Author(s):  
◽  
R. Jagadeesh ◽  
Nirmala Vaz
Keyword(s):  
Fractional Order ◽  
Reaction Rate ◽  
Oxidation Products ◽  
Solvent Isotope Effect ◽  
Experimental Conditions ◽  
Isokinetic Relationship ◽  
Mechanistic Approach ◽  
Chloramine T ◽  
Solvent Isotope ◽  
Kinetics Of

AbstractThe kinetics of the oxidation of five catecholamines viz., dopamine (A), L-dopa (B), methyldopa (C), epinephrine (D) and norepinephrine (E) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in presence of HClO4 was studied at 30±0.1 °C. The five reactions followed identical kinetics with a first-order dependence on [CAT]o, fractional-order in [substrate]o, and inverse fractional-order in [H+]. Under comparable experimental conditions, the rate of oxidation of catecholamines increases in the order D>E>A>B>C. The variation of ionic strength of the medium and the addition of p-toluenesulfonamide or halide ions had no significant effect on the reaction rate. The rate increased with decreasing dielectric constant of the medium. The solvent isotope effect was studied using D2O. A Michaelis-Menten type mechanism has been suggested to explain the results. Equilibrium and decomposition constants for CAT-catecholamine complexes have been evaluated. CH3C6H4SO2NHCl of the oxidant has been postulated as the reactive oxidizing species and oxidation products were identified. An isokinetic relationship is observed with β=361 K, indicating that enthalpy factors control the reaction rate. The mechanism proposed and the derived rate law are consistent with the observed kinetics.

KINETICS OF THE OXIDATION OF URANIUM(IV) BY MOLECULAR OXYGEN IN AQUEOUS PERCHLORIC ACID SOLUTION

1956 ◽  
Vol 34 (10) ◽  
pp. 1419-1427 ◽  
Author(s):  
J. Halpern ◽  
J. G. Smith
Keyword(s):  
Reaction Mechanism ◽  
Acid Solution ◽  
Molecular Oxygen ◽  
Perchloric Acid ◽  
Chain Reaction ◽  
Perchloric Acid Solution ◽  
Aqueous Perchloric Acid ◽  
A Chain ◽  
Kinetics Of ◽  
Considerable Range

The kinetics of the oxidation of uranium(IV) by molecular oxygen in aqueous perchloric acid solution were studied. Over a considerable range of conditions, the results are fitted approximately by the rate law:−d[UIV]/dt = k[UIV] [O2]/[H+], where k ≈ 2 × 1014 exp[−22,000/RT]sec.−1. The reaction is catalyzed by Cu++ and inhibited by small amounts of Ag+ and Cl−. The results are interpreted in terms of a chain reaction mechanism involving UO2+ and HO2 as chain carriers.

The mechanism of the oxidative deamination and decarboxylation of serine and threonine by periodate in acid medium

1985 ◽  
Vol 63 (9) ◽  
pp. 2349-2353 ◽  
Author(s):  
Rosa Pascual ◽  
Miguel A. Herráez
Keyword(s):  
Amino Acid ◽  
Acid Medium ◽  
Rate Constants ◽  
Reaction Rate ◽  
Oxidative Deamination ◽  
Experimental Conditions ◽  
Kinetics Of Oxidation ◽  
Rate Law ◽  
First Order ◽  
Kinetics Of

The kinetics of oxidation of serine and threonine by periodate have been investigated in acid medium at 10 °C. The reaction rate is first order in both periodate and amino acid, and the overall reaction follows second-order kinetics. The rates decrease with increase in [H+]. A catalytic effect of the buffers was not observed in the oxidation process. An analysis of the dependence of the rate on [H+] reveals that the reactive species under the experimental conditions are periodate monoanion and dianion and the dipolar form of the amino acid. The mechanism proposed and the derived rate law are consistent with the observed kinetics. The rate constants predicted using the derived rate law are in agreement with the observed rate constants, thus justifying this rate law and hence the proposed mechanistic scheme.

Sign in / Sign up

Export Citation Format

Share Document