THE PHOTOLYSIS OF AZOETHANE

1958 ◽  
Vol 36 (2) ◽  
pp. 344-353 ◽  
Author(s):  
H. Cerfontain ◽  
K. O. Kutschke
Keyword(s):  
Activation Energy ◽  
Quantum Yield ◽  
Addition Reaction ◽  
Kcal Mole ◽  
A Value ◽  
Ethyl Radicals

The photolysis of azoethane at λ 3660 Å has been reinvestigated. The quantum yield of nitrogen formation was found to be dependent on the azoethane pressure and the temperature, indicating collisional deactivation of excited azoethane molecules.The results confirm the mechanism proposed by Ausloos and Steacie (1). For the activation energy of the addition reaction C2H5 + C2H5N2C2H5 a value of 6.0 ± 0.3 kcal./mole has been obtained, assuming a negligible activation energy for the combination reaction of two ethyl radicals.

THE REACTION OF METHYL RADICALS WITH FORMALDEHYDE

1959 ◽  
Vol 37 (9) ◽  
pp. 1462-1468 ◽  
Author(s):  
A. R. Blake ◽  
K. O. Kutschke
Keyword(s):  
Activation Energy ◽  
Kinetic Analysis ◽  
Addition Reactions ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
A Value ◽  
Abstraction Reaction ◽  
Butyl Peroxide

The pyrolysis of di-t-butyl peroxide has been reinvestigated and used as a source of methyl radicals to study the abstraction reaction between methyl radicals and formaldehyde. At low [HCHO]/[peroxide] ratios the system was simple enough for kinetic analysis, and a value of 6.6 kcal/mole was obtained for the activation energy. At higher [HCHO]/[peroxide] ratios the system became very complicated, possibly due to the increased importance of addition reactions.

ADDITION OF ETHYL RADICALS TO ETHYLENE

1957 ◽  
Vol 35 (7) ◽  
pp. 588-594 ◽  
Author(s):  
J. A. Pinder ◽  
D. J. Le Roy
Keyword(s):  
Activation Energy ◽  
Reaction Zone ◽  
Addition Reaction ◽  
Steric Factor ◽  
Square Root ◽  
Temperature Range ◽  
Ethyl Radical ◽  
Ethyl Radicals

The addition of ethyl radicals to ethylene has been studied in the temperature range 58° to 123 °C. The radicals were produced by the mercury photosensitized decomposition of hydrogen in the presence of ethylene, and the rate of the addition reaction was measured in terms of the rate of formation of n-hexane by the combination of ethyl and butyl radicals. Corrections were made for the non-uniformity of radical concentrations in the reaction zone. Assuming a negligible activation energy for the combination of two ethyl radicals, the activation energy for the addition reaction is 5.5 kcal. per mole; the steric factor, relative to the square root of the steric factor for ethyl radical combination, is 5.0 × 10−5.

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.

PHOTOLYSIS OF 2, 2′, 4, 4′-TETRADEUTERODIETHYL KETONE

1951 ◽  
Vol 29 (12) ◽  
pp. 1092-1103 ◽  
Author(s):  
M. H. J. Wijnen ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Diethyl Ketone ◽  
Temperature Range ◽  
A Value ◽  
Ethyl Radicals

The photolysis of CH3CD2COCD2CH3 has been studied over a temperature range from 25°C. to 365°C. The results confirm several features of the mechanism, previously proposed for the photolysis of diethyl ketone. It is concluded that disproportionation of ethyl radicals occurs by a "head to tail" mechanism. As activation energy for the reaction[Formula: see text]a value E4 = 8.7 kcal. was found. As activation energy for Reaction (5)[Formula: see text]a value of E5 = 11.7 kcal. was found. An activation energy of ∼ 17 kcal. is estimated for the thermal decomposition of the pentanonyl radical

Creep of Pure-Gum Rubber Vulcanizates from Indentation-Time Measurements

1963 ◽  
Vol 36 (3) ◽  
pp. 611-620 ◽  
Author(s):  
L. A. Wood ◽  
F. L. Roth
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Polymer Network ◽  
Absolute Temperature ◽  
Styrene Butadiene Rubber ◽  
Rigid Sphere ◽  
Butadiene Rubber ◽  
Kcal Mole ◽  
A Value ◽  
Styrene Butadiene

Abstract The compliance J (limit of the ratio of strain to stress at zero deformation) has been determined from measurements of the indentation of a flat rubber surface by a rigid sphere, as a function of time t and temperature T. The results are subjected to two successive operations: (1) Jis multiplied by the absolute temperature T and (2) an empirically-determined number is added to the logarithm of the time at each temperature to make the values of JT agree as well as possible. For natural rubber from 25° to −40° C the shift required appears to correspond to a constant “activation energy” of 38kcal/mole; from −40° to − 60° C the shift is in quite good agreement with that predicted by the equation of Williams, Landel, and Ferry. Butyl rubber yields an “activation energy” of 20 kcal/mole while styrene-butadiene rubber gives a value of 22 kcal/mole. The resulting curve of JT against log t shows a sigmoid form with an increase of slope over 2 to 3 decades and a decrease at higher values. There is usually an extended region of nearly constant slope corresponding to the conditions of normal use of rubber products. For natural rubber this slope is 1 to 2% per decade; for the synthetics it is appreciably higher, reaching a value of 15% per decade for nitrile rubber. This behavior differs from that of a classical idealized polymer network, for which the compliance would approach an equilibrium value at long times.

KINETICS OF THE DECOMPOSITIONS OF ETHANE AND PROPANE SENSITIZED BY AZOMETHANE: THE DECOMPOSITION OF THE NORMAL PROPYL RADICAL

1966 ◽  
Vol 44 (24) ◽  
pp. 2927-2940 ◽  
Author(s):  
M. C. Lin ◽  
K. J. Laidler
Keyword(s):  
Activation Energy ◽  
Satisfactory Agreement ◽  
Rate Constant ◽  
Dissociation Energy ◽  
Low Temperatures ◽  
Heats Of Formation ◽  
Kcal Mole ◽  
Energy Diagram ◽  
A Value ◽  
Kinetics Of

The azomethane-sensitized pyrolysis of ethane was studied at low temperatures from 280 to 350 °C. Measurements were made of initial rates of formation of methane, nitrogen, and butane. From the rate of nitrogen production the rate constant for the azomethane decomposition into 2CH3 + N2 was[Formula: see text]A similar study of the propane decomposition, at temperatures from 260 to 300 °C, led to the value[Formula: see text]in satisfactory agreement. The rate of decomposition of the n-propyl radical into CH3 and C2H4 was obtained by comparing the rates of formation of C2H4 and n-C6H14; the rate constant was[Formula: see text]The activation energy of 31.4 kcal/mole, together with that of 8.9 kcal/mole for the reverse reaction obtained by Brinton, leads to a value of 20.3 kcal/mole for the dissociation energy of n-CH3—CH CH2 at 0 °K, and to a value of 22.8 at 25 °C. The corresponding values for the heats of formation 2of the n-propyl radical are 28.4 kcal/mole at 0 °K, and 23.1 kcal/mole at 25 °C. The dissociation energy of n-CH3CH2CH2—H is deduced to be 99.4 kcal/mole at 0 °K and 99.9 kcal/mole at 25 °C. An energy diagram is constructed for the various reactions of n-C3H7 and i-C3H7.

THE REACTION OF METHYL RADICALS WITH ISOBUTANE

1953 ◽  
Vol 31 (5) ◽  
pp. 505-510 ◽  
Author(s):  
M. H. Jones ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Energy Of Activation ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
A Value ◽  
Photochemical Decomposition

An investigation is reported of the reaction of methyl radicals, produced in the photochemical decomposition of azomethane, with isobutane. The energy of activation of this process was found to be 6.7 ± 0.8 kcal./mole, assuming that the combination of methyl radicals has an activation energy of zero. From some experiments with n-butane, a value of 9 ± 1 kcal./mole was obtained.

Reactions of the ethyl radical. III. The effect of deuteration upon the metathetical reaction

1958 ◽  
Vol 245 (1243) ◽  
pp. 470-480 ◽  
Keyword(s):  
Activation Energy ◽  
Frequency Factor ◽  
Isotopic Effect ◽  
Methyl Radical ◽  
Kcal Mole ◽  
Ethyl Radical ◽  
A Value ◽  
Significant Difference ◽  
The Mean ◽  
Methylene Group

The photolysis of 3-pentanone- d 10 has been studied over a temperature range from 25 to 314°C, and the kinetic results agree closely with those observed with 2, 2, 4, 4-(3-pentanone)- d 4 . The reaction Et ⋅ + Me ⋅CD 2 ⋅CO.CD 2 ⋅ Me → Et ⋅D + Me ⋅CD⋅CO⋅CD 2 ⋅ Me is common to both systems and no significant difference was found between the two possible values, either of the energy of activation or of the frequency factor. A value of 1⋅6 kcal/mole was found for the mean difference in activation energy for the abstraction of D or H, respectively, by the ethyl radical from the α -methylene group of 3-pentanone (- d 10 , - d 4 or - d 0 ). This agrees well with the corresponding value of 1⋅6 kcal/mole for the abstraction of D or H by the methyl radical from acetone (- d 6 or - d 0 ). All five reactions share the same value of the frequency factor within the limits of experimental error. We may conclude that an appreciable isotopic effect is observed only when the substitution of D for H has increased the strength of the bond to be broken, and that this effect is an increase in the activation energy alone, the frequency factor remaining unaltered.

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

The slow oxidation of methane

1956 ◽  
Vol 235 (1201) ◽  
pp. 158-173 ◽  
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Induction Period ◽  
Hydrofluoric Acid ◽  
Pressure Rise ◽  
Pressure Change ◽  
Kcal Mole ◽  
Gaseous Products ◽  
Oxidation Of Methane ◽  
Reproducible Manner

Mixtures of methane and oxygen behave in a reproducible manner at temperatures of 440 to 520°C and initial pressures of 100 to 350 mm when reacting in Pyrex vessels freshly cleaned with hydrofluoric acid. The apparent order of the reaction ranged from 2∙3 to 2∙6 and the overall activation energy from 29 to 41 kcal/mole. Analyses of the products formed have been made, together with measurements of pressure change. Formaldehyde is formed from the commencement of the reaction including the induction period, but its concentra­tion reaches a maximum near the stage where the pressure rise is a maximum, and then falls off. Hydrogen peroxide is also formed, less rapidly in the earliest stage, but its rate of formation overtakes that of formaldehyde and it reaches an even higher concentration. No other peroxides were detected, nor was methanol found. Hydrogen was present in the gaseous products. These observations are not in full accord with some of the conclusions derived from earlier investigations.

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