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.

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.

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 VAPOR PHASE PHOTOLYSIS OF HEXAFLUOROACETONE IN THE PRESENCE OF METHANE AND ETHANE

1955 ◽  
Vol 33 (5) ◽  
pp. 743-749 ◽  
Author(s):  
P. B. Ayscough ◽  
J. C. Polanyi ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Vapor Phase ◽  
Activation Energies ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Photolytic Decomposition

The photolytic decomposition of hexafluoroacetone by light of wavelength 3130 Å has been used to produce trifluoromethyl radicals for a study of their reactions with methane and ethane. It has been shown that these radicals abstract hydrogen with greater facility than do methyl radicals. The activation energies for the two reactions[Formula: see text]and[Formula: see text]are found to be 10.3 ± 0.5 kcal./mole and 7.5 ±0.5 kcal./mole respectively, if one can assume zero activation energy for the recombination of trifluoromethyl radicals.

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.

THE PYROLYSIS OF TRIMETHYLTHALLIUM

1965 ◽  
Vol 43 (7) ◽  
pp. 1961-1967 ◽  
Author(s):  
M. G. Jacko ◽  
S. J. W. Price
Keyword(s):  
Activation Energy ◽  
Rate Constant ◽  
Total Pressure ◽  
Flow System ◽  
Total Darkness ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Homogeneous Process ◽  
Carrier Flow ◽  
Reaction Proceeds

The pyrolysis of trimethylthallium has been studied in a toluene carrier flow system from 458 to 591 °K using total pressures from 5.6 to 33.0 mm. The progress of the reaction was followed by measuring the amount of methane, ethane, ethylene, and ethylbenzene formed and, in 21 runs, by direct thallium analysis. All preparative and kinetic work was carried out in total darkness where possible. A shielded 10 W lamp was used when some illumination was necessary.The decomposition is approximately 80% heterogeneous in an unconditioned vessel and 14–27% heterogeneous in a vessel pretreated with hot 50% HF for 10 min. The reaction proceeds by the simple consecutive release of three methyl radicals. The rate constant depends only slightly on the total pressure in the system so that the activation energy of the homogeneous process, 27.4 kcal/mole, may be equated to D[(CH3)2Tl—CH3].

THE REACTION OF METHYL RADICALS WITH FORMALDEHYDE

1959 ◽  
Vol 37 (4) ◽  
pp. 672-678 ◽  
Author(s):  
S. Toby ◽  
K. O. Kutschke
Keyword(s):  
Activation Energy ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Formyl Radical ◽  
Temperature Range ◽  
Abstraction Reaction

Azomethane was photolyzed in the presence of up to 30 mole per cent formaldehyde and formaldehyde-d2 at temperatures from 80 °C to 180 °C. The value of the activation energy for the abstraction reaction with methyl radicals was found to be 6.2 kcal mole−1 for CH2O and 7.9 kcal mole−1 for CD2O. The results indicated that the formyl radical was stable over the temperature range studied.

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.

THE REACTIONS OF METHYL RADICALS WITH CYCLOPROPANE, ETHYLENE OXIDE, METHANOL, AND DIMETHYL ETHER

1950 ◽  
Vol 28b (7) ◽  
pp. 395-402 ◽  
Author(s):  
M. K. Phibbs ◽  
B. deB. Darwent
Keyword(s):  
Ethylene Oxide ◽  
Dimethyl Ether ◽  
Activation Energies ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Photochemical Decomposition

The reactions of methyl radicals, produced by the photochemical decomposition of dimethylmercury, with cyclopropane, ethylene oxide, methanol and dimethyl ether have been investigated between 100° and 250 °C. The following activation energies (kcal. mole−1) for the abstraction of hydrogen from the compounds by methyl radicals were found: cyclopropane, 10.2; ethylene oxide 9.6; methanol, 8.2; and dimethyl ether, 8.0. The probability factors have been shown to be about 10−4 for all the compounds investigated.

Reactions of trifluoromethyl and methyl radicals with ethylene oxide

1970 ◽  
Vol 48 (22) ◽  
pp. 3601-3604 ◽  
Author(s):  
S. H. Jones ◽  
E. Whittle
Keyword(s):  
Activation Energy ◽  
Ethylene Oxide ◽  
Published Data ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Arrhenius Parameters

The reaction between CF3 radicals and ethylene oxide was studied in the range 60–228 °C using CF3I as a radical source. For the reactions,[Formula: see text]we obtain[Formula: see text]where θ = 2.3 RT kcal mole−1Published data of Phibbs and Darwent on the reaction[Formula: see text]have been re-calculated and it is suggested that both the original and re-calculated values of the activation energy E5 are too low. The Arrhenius parameters for the reactions of CF3 and CH3 radicals with ethylene oxide are compared with those for related reactions.

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.

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