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 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.

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 Vulcanization of Elastomers. XI. The Vulcanization of Natural Rubber with Sulfur in the Presence of Mercaptobenzothiazole. I

1957 ◽  
Vol 30 (3) ◽  
pp. 911-927 ◽  
Author(s):  
Otto Lorenz ◽  
Elisabeth Echte
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Natural Rubber ◽  
Kinetic Analysis ◽  
Rate Constants ◽  
Network Formation ◽  
Zinc Salt ◽  
Kcal Mole ◽  
Minimum Quantity ◽  
First Order

Abstract 1. The decrease of free sulfur occurs according to the first order law during the vulcanization of natural rubber accelerated by mercaptobenzothiazole in the presence of zinc oxide. The activating energy for this reaction amounts to 30.5 kcal./mole. 2. If zinc benzothiazolylmercaptide is used as an accelerator, one obtains the same rate constants for the sulfur decrease as in the presence of mercaptobenzothiazole. These seem to be equivalent as regards their effectiveness of acceleration. 3. A kinetic analysis of the reciprocal swelling, which represents a measure of network formation, indicates that the reaction is first order. Sulfur decrease and reciprocal swelling prove to be equal processes as regards rate. This is true where vulcanization is accelerated with mercaptobenzothiazole or with the zinc salt. 4. During vulcanization there occurs a decrease of accelerator concentration. This is dependent upon the temperature and is tied in with the combination sulfur with rubber. 5. If the quantity of the accelerator added is changed, the rate constants for sulfur decrease and for reciprocal swelling do not change, provided that a minimum quantity of accelerator is present. 6. In vulcanization accelerated with zinc benzothiazolylmercaptide, zinc oxide being absent, sulfur decrease again occurs according to the first order law but considerably faster, without thereby changing the activation energy. These investigations are being continued and the results will be discussed in detail in relation to other published contributions in this field.

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.

Hemolytic decomposition of di-sec-butyl peroxide

1970 ◽  
Vol 48 (4) ◽  
pp. 615-627 ◽  
Author(s):  
R. Hiatt ◽  
Sandor Szilagyi
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Hydrogen Production ◽  
Methyl Ethyl Ketone ◽  
Methyl Ethyl ◽  
Kcal Mole ◽  
Alkoxy Radicals ◽  
Solvent Cage ◽  
Butyl Peroxide

Rates and products have been determined for the thermal decomposition of sec-butyl peroxide at 110–150 °C in several solvents.The decomposition was shown to be unimolecular with energies of activation in toluene, benzene, and cyclohexane of 35.5 ± 1.0, 33.2 ± 1.0, 33.8 ± 1.0 kcal/mole respectively. The activation energy of thermal decomposition for the deuterated peroxide was found to be 37.2 + 1.0 kcal/mole in toluene.About 70–80% of the products could be explained by known reactions of free alkoxy radicals, and very little, if any, disproportionation of two sec-butoxy radicals in the solvent cage could be detected.The other 20–30% of the peroxide yielded H2 and methyl ethyl ketone. The yield of H2 was unaffected by the nature or the viscosity of the solvent, but H2 was not formed when s-Bu2O2 was photolyzed in toluene at 35 °C nor when the peroxide was thermally decomposed in the gas phase.α,α′-Dideutero-sec-butyl peroxide was prepared and decomposed in toluene at 110–150 °C. The yield of D2 was about the same as the yield of H2 from s-Bu2O2, but the rate of decomposition (at 135 °C) was only 1/1.55 as fast.Mechanisms for hydrogen production are discussed, but none satisfactorily explains all the evidence.

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 kinetics of the ordering process in triclinic NaAlSi3O8

1960 ◽  
Vol 32 (249) ◽  
pp. 436-454 ◽  
Author(s):  
J. D. C. McConnell ◽  
Duncan McKie
Keyword(s):  
Activation Energy ◽  
Kinetic Analysis ◽  
Vapour Pressure ◽  
Polymorphic Transformation ◽  
Water Vapour Pressure ◽  
Kcal Mole ◽  
Temperature Range ◽  
Self Diffusion ◽  
Dry Heating ◽  
Kinetics Of

SummaryA kinetic analysis is presented of the data of MacKenzie (1957) on the hydrothermal treatment of NaAlSi3O8 under isobaric, isothermal conditions in the temperature range 450° C. to 1000° C.The analysis indicates the existence of a smeared polymorphic transformation in the temperature range around 600° C. The activation energy for the transformation is about 60 kcal. mole−1 and has been equated with the process of self-diffusion involved in Al-Si ordering in the structure. Some dry-heating experiments and the influence of varying water vapour pressure are discussed.

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.

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