POLYMÉRISATION PAR LES RAYONS-X DU CHLORURE DE VINYLE À L'ÉTAT DE VAPEUR

1963 ◽  
Vol 41 (6) ◽  
pp. 1578-1587 ◽  
Author(s):  
Jan A. Herman ◽  
Pierre M. Hupin
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Average Molecular Weight ◽  
Negative Temperature ◽  
Solid Polymer ◽  
X Rays ◽  
Kcal Mole ◽  
Rate Of Polymerization ◽  
G Value ◽  
Termination Process

The polymerization of vinyl chloride in the gas phase by X rays gives a solid polymer of 1140 average molecular weight. The G value of monomer disappearance varies from 100 to 400 and depends on pressure and temperature. From the measure of the rate of polymerization it was possible to deduce the activation energy of the chain propagation steps: 2.5 kcal/mole, and that of the hindered termination process: 7.4 kcal/mole. The negative temperature co-efficient of the polymerization is explained by the importance of this hindered termination process.

The Langmuir-Hinshelwood Reaction between Oxygen and CO at Ir(111) Surfaces

1979 ◽  
Vol 34 (1) ◽  
pp. 81-88 ◽  
Author(s):  
J. Küppers ◽  
A. Plagge
Keyword(s):  
Activation Energy ◽  
Computer Program ◽  
Apparent Activation Energy ◽  
Gas Phase ◽  
Close Agreement ◽  
Reaction Path ◽  
Kcal Mole ◽  
Reaction Step ◽  
Per Se ◽  
Reaction Processes

Abstract The reaction of oxygen and CO to form CO2 has been investigated using an Ir (111) surface as an acting catalyst. Both instationary and stationary reaction processes have been established via separate gas exposing techniques. The instationary reaction process, achieved from coadsorbed CO and O which per se is an LH reaction is found to be controlled by an apparent activation energy of 10.7 kcal/mole. The stationary reaction with both CO and O2 continuously present in the gas phase has been simulated using a proper computer program, involving both LH and ER reaction steps. By comparison with experimental results, close agreement is found when ruling out any ER reaction step from the reaction path.

Gas phase photochlorination of perfluorocyclohexene

1969 ◽  
Vol 47 (6) ◽  
pp. 1067-1069 ◽  
Author(s):  
J. J. Cosa ◽  
C. A. Vallana ◽  
E. H. Staricco
Keyword(s):  
Activation Energy ◽  
Quantum Yield ◽  
Gas Phase ◽  
Photochemical Reaction ◽  
Total Pressure ◽  
Square Root ◽  
Kcal Mole ◽  
Kinetics Of

The kinetics of the gas phase photochemical reaction between perfluorocyclohexene and chlorine was studied between 10 and 50 °C. The system was irradiated with light of 4360 Å. The rate of the photochlorination was independent of the perfluorocyclohexene pressure and of the total pressure. It was found to be proportional to the first power of the pressure of Cl2 and to the square root of the intensity of absorbed light. At 30 °C, the quantum yield was found to be 200 when the initial Cl2 pressure was 100 Torr, and intensity of light absorbed 9.89 × 10−9 einstein l−1s−1.An activation energy of 5.1 kcal/mole could be assigned to the reaction C6F10Cl + Cl2.

THE THERMAL DECOMPOSITION OF METHYL HYDROPEROXIDE

1965 ◽  
Vol 43 (8) ◽  
pp. 2236-2242 ◽  
Author(s):  
Alexander D. Kirk
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Gas Phase ◽  
Rate Constants ◽  
Dimethyl Phthalate ◽  
Kcal Mole ◽  
First Order ◽  
Methyl Hydroperoxide ◽  
Expected Values ◽  
Homogeneous Decomposition

The thermal decomposition of methyl hydroperoxide has been studied in solution and in the gas phase. The decomposition was found to be partly heterogeneous in solution in dimethyl phthalate and no reliable rate constants were obtained. Use of the toluene carrier method for the gas phase work enabled measurement of the rate constant for the homogeneous decomposition. The first order rate constants obtained range from 0.19 s−1 at 292 °C to 1.5 s−1 at 378 °C, leading to log A, 11± 2, and activation energy, 32 ± 5 kcal/mole. These results are compared with the expected values of log A, 13–14, and activation energy, 42 kcal/mole. The significance of these findings is discussed.

THE GAS PHASE REACTION OF METHYL RADICALS WITH HEXAFLUOROACETONE

1957 ◽  
Vol 35 (10) ◽  
pp. 1216-1224 ◽  
Author(s):  
G. O. Pritchard ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Gas Phase ◽  
Steric Factor ◽  
Phase Reaction ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Gas Phase Reaction

The photolytic and thermal decomposition of azomethane in the presence of hexafluoroacetone produces small amounts of fluorinated products, mainly fluoroform. The mechanism of this and related reactions is discussed. It is concluded that the proposed reaction.[Formula: see text]has an activation energy of about 6 kcal./mole, with a steric factor of about 10−5.

Über Reaktionen zwischen Phosphortrichlorid und Cyclohexen unter dem Einfluß von Y-Strahlung und von Wärme

1964 ◽  
Vol 19 (11) ◽  
pp. 999-1005 ◽  
Author(s):  
K. Wunder ◽  
H. Drawe ◽  
A. Henglein
Keyword(s):  
Activation Energy ◽  
Dose Rate ◽  
Phosphorus Trichloride ◽  
Square Root ◽  
Kcal Mole ◽  
Chain Reaction ◽  
Rate Determining Step ◽  
Γ Rays ◽  
G Value

1-chlorocyclohexyl-phosphorus dichloride is formed in a Kharasch type chain reaction when γ-rays act on mixtures of phosphorus trichloride and cyclohexene. The G-value is proportional to the reciprocal square root of the dose rate and reaches a maximum at 100°C. The activation energy of the rate determining step PCl2C6H10 · +PCl3→PCl2C6H10Cl+PCl2 · was found to amount to 6, 7 kcal/mole. At higher temperatures, the yield strongly decreases since another chain reaction predominates which produces cyclohexyl-phosphorus dichloride. The two chains have a common propagation step. 1-chlorocyclohexyl-phosphorus dichloride and cyclohexyl-phosphorus dichloride are also thermally formed at temperatures above about 150°C.

A thermocouple method of following the non-stationary state of chemical reactions - II. The evaluation of velocity coefficients and energies of activation for the propagation and termination reactions for the initial and later stages of the polymerization of vinyl acetate

1955 ◽  
Vol 230 (1183) ◽  
pp. 429-447 ◽  
Keyword(s):  
Activation Energy ◽  
Vinyl Acetate ◽  
Viscous Medium ◽  
Energy Of Activation ◽  
Solid Polymer ◽  
Polymer Gel ◽  
Kcal Mole ◽  
Continuous Increase ◽  
Diffusion Controlled ◽  
Thermocouple Method

A study has been made of the changes which occur in the velocity coefficients and energies of activation for the propagation and termination reactions in the polymerization of vinyl acetate, photosensitized with 0·0009 mole/1. 1. 1'-azo-bis- cyclo hexanecarbonitrile. The rate of polymerization increases from the early stages of the reaction until about 50% conversion and subsequently decreases rapidly to an extremely low value at about 75% conversion, while the overall energy of activation decreases from 4·2 kcal/mole initially to 1·9 kcal/mole at 50% conversion and then increases rapidly as the polymerization continues towards completion. This decrease in the overall energy of activation is due to a continuous increase in the activation energy for the termination reaction as the polymerization progresses, and this is believed to be due to an increase in the activation energy for the diffusion of polymer radicals in the increasingly viscous medium. Beyond 50% conversion the activation energy for the propagation reaction begins to increase, presumably due to the propagation step becoming diffusion controlled as the system becomes a solid polymer gel. The energies of activation for the propagation and termination reactions have been shown to vary from less than 5 and 1 kcal/mole respectively initially, to values of greater than 14 kcal/mole at about 70% conversion.

THE GAS PHASE PHOTOLYSIS OF ACETIC AND PROPIONIC ANHYDRIDE

1956 ◽  
Vol 34 (12) ◽  
pp. 1709-1713 ◽  
Author(s):  
P. Ausloos
Keyword(s):  
Activation Energy ◽  
Acetic Anhydride ◽  
Gas Phase ◽  
Temperature Region ◽  
Equal Probability ◽  
Kcal Mole ◽  
Propionic Anhydride ◽  
Abstraction Reaction ◽  
Photochemical Decomposition

The photolysis of acetic anhydride has been reinvestigated in the temperature region from 30 to 195 °C. Two primary processes occur with about equal probability:[Formula: see text]Analogous primary processes have been proposed for the photochemical decomposition of propionic anhydride.The abstraction reaction:[Formula: see text]is of importance, and the results indicate that it has an activation energy of about 9.6 kcal./mole.

Elementary processes in the acetaldehyde pyrolysis

1968 ◽  
Vol 46 (4) ◽  
pp. 479-490 ◽  
Author(s):  
Michael T. H. Liu ◽  
K. J. Laidler
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Gas Phase ◽  
Rate Constants ◽  
Major Product ◽  
Quantum Mechanical ◽  
Kcal Mole ◽  
Elementary Processes ◽  
Kinetic Effects ◽  
Ethane Formation

The acetaldehyde pyrolysis has been studied over the 480–540 °C temperature range, and at pressures from 1 to 560 mm Hg. Measurements were made of the rates of production of the major product methane and of the minor products hydrogen, ethane, acetone, and propionaldehyde. The kinetic effects of adding carbon dioxide, of changing the surface:volume ratio, and of coating the vessel have been determined. The elementary processes are found to occur largely in the gas phase. The dissociation of CH3CHO into CH3 + CHO is deduced from the rates of hydrogen and ethane formation; there is significant falling off of the rate constants at lower pressures. The kinetic parameters for the reaction CH3 + CH3CHO → CH4 + CH3CO are obtained, and it is suggested that quantum-mechanical tunnelling plays a role. Acetone production has an activation energy of 12.4 kcal/mole and it is concluded that its formation involves the participation of the isopropoxy radical, the activation energies being as indicated:[Formula: see text]

DECOMPOSITION PRESSURES OF FERRIC SULPHATE AND ALUMINUM SULPHATE

1960 ◽  
Vol 38 (11) ◽  
pp. 2196-2202 ◽  
Author(s):  
N. A. Warner ◽  
T. R. Ingraham
Keyword(s):  
Gas Phase ◽  
Static System ◽  
Ferric Sulphate ◽  
Kcal Mole ◽  
Aluminum Sulphate ◽  
Temperature And Pressure ◽  
Pressure Changes ◽  
Mercury Manometer ◽  
Decomposition Pressure ◽  
Gas Pressures

The gas pressures over samples of anhydrous ferric sulphate and anhydrous aluminum sulphate have been measured in a static system, using a mercury manometer in which the exposed surface was covered with a flexible Pyrex bellows. The calculated ΔH for the decomposition of Fe2(SO4)3 was +135.4 kcal/mole. It was not possible to calculate the ΔH for the Al2(SO4)3 decomposition, because a discrete aluminum oxide with singular thermodynamic properties was not obtained.In the Fe2(SO4)3 system, the fraction of SO3 in the gas phase was found to be almost constant over the range of temperature and pressure changes used in the study.At any given temperature, the decomposition pressure over a ferric sulphate sample is greater than that over an aluminum sulphate sample, thus indicating that preferential decomposition of ferric sulphate should be thermodynamically feasible in mixtures of ferric sulphate and aluminum sulphate.

Sign in / Sign up

Export Citation Format

Share Document