The activation energy and the steric factor of the reaction between methyl radicals and toluene

1950 ◽  
Vol 46 ◽  
pp. 625 ◽  
Author(s):  
M. Szwarc ◽  
J. S. Roberts
Keyword(s):  
Activation Energy ◽  
Steric Factor ◽  
Methyl Radicals

THE PHOTO-OXIDATION OF AZOMETHANE

1955 ◽  
Vol 33 (3) ◽  
pp. 496-506 ◽  
Author(s):  
G. R. Hoey ◽  
K. O. Kutschke
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Room Temperature ◽  
Major Product ◽  
Steric Factor ◽  
Primary Process ◽  
Methyl Radicals ◽  
Low Oxygen ◽  
Secondary Product ◽  
Photo Oxidation

The photo-oxidation of azomethane has been studied at low oxygen pressures (0.02 to 1 mm.) in the temperature range ca. 25 °C. to 161 °C. The primary process in the normal photolysis of azomethane is essentially unaffected by the presence of oxygen. Carbon monoxide is probably a secondary product of the oxidation of methyl radicals. Carbon dioxide formation is quite small, and therefore neither methyl radicals nor CH3N=N—CH2 radicals are oxidized appreciably to carbon dioxide. Nitrous oxide, which is a major product of the oxidation, is most likely formed from the oxidation of CH3N=NCH2 radicals. The suggested mechanism of N2O formation is:[Formula: see text] The reaction of methyl radicals with oxygen was found to proceed with a negligible activation energy and a steric factor of the order of 10−2. Evidence for the occurrence of the reactions[Formula: see text]at room temperature was obtained.

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 mechanism of the photolysis of acetamide

1957 ◽  
Vol 239 (1216) ◽  
pp. 1-15 ◽  
Keyword(s):  
Activation Energy ◽  
Steric Factor ◽  
Primary Process ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Subsequent Reaction

An investigation of the photolysis of acetamide has been made using light in the 2500 Å region of the spectrum. The main primary process is the breakdown of the molecule into CH 3 and CONH 2 radicals, but this is probably accompanied by a second process yielding CH 3 CN and H 2 O. The methyl radicals react both with acetamide and with CONH 2 radicals to give methane and recombine to give ethane. The CONH 2 radicals may decompose both spontaneously and thermally to give CO and NH 2 radicals. The subsequent reaction of the NH 2 radicals with acetamide gives ammonia. With acetone as a source of methyl radicals, the activation energy for the abstraction of hydrogen by this radical was found to be 9⋅2 kcal/mole and the steric factor ~ 4 x 10 -4 .

PHOTOLYSIS OF ACETONE – HYDROGEN HLORIDE MIXTURES

1953 ◽  
Vol 31 (2) ◽  
pp. 158-170 ◽  
Author(s):  
R. J. Cvetanović ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Hydrogen Chloride ◽  
Room Temperature ◽  
Steric Factor ◽  
Methyl Radicals ◽  
Strong Suppression ◽  
Upper Limit ◽  
Ethane Formation

The photolysis of acetone – hydrogen chloride mixtures has been investigated at 150 °C. and at room temperature. A strong suppression of ethane formation with a corresponding large increase in the formation of methane results from additions of relatively very small amounts of hydrogen chloride to acetone. The importance of the reactions[Formula: see text]and[Formula: see text]has been demonstrated. The collision yield of reaction (1) at 28 °C. is 2 × 10−4, and, therefore, the upper limit for E1 is 5.1 kcal. per mole. The effects observed at 150° and 28° indicate that, on the assumption of a zero activation energy and a steric factor of unity for combination of methyl radicals, E1 = 2.1 ± 1 kcal. per mole, and P1 is approximately 7 × 10−3.

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.

Aromatic oxidation by cobaltic acetate in acetic acid

1969 ◽  
Vol 47 (3) ◽  
pp. 387-392 ◽  
Author(s):  
Koichiro Sakota ◽  
Yoshio Kamiya ◽  
Nobuto Ohta
Keyword(s):  
Activation Energy ◽  
Electron Transfer ◽  
Acetic Acid ◽  
Bond Energy ◽  
Hydrogen Abstraction ◽  
Steric Factor ◽  
Benzyl Acetate ◽  
Kcal Mole ◽  
First Order ◽  
Reversible Electron Transfer

A detailed kinetic study of oxidation of toluene and its derivatives by cobaltic acetate in 95 vol% acetic acid is reported. The reaction was found to be profoundly affected by a steric factor and rather insensitive to the C—H bond energy. The order of reactivities of various alkylbenzenes is quite reversal to that of hydrogen abstraction reactions. The reaction was of first-order with respect to toluene, of second-order with respect to cobaltic ion and of inverse first-order with respect to cobaltous ion. The oxidation by cobaltic ion seems to proceed via an initial reversible electron transfer from toluene to cobaltic ion, yielding [Formula: see text] which is oxidized into benzyl acetate by another cobaltic ion. The apparent activation energy for toluene was found to be 25.3 kcal mole−1, and the same activation energy was found for ethylbenzene, cumene, diphenylmethane, and triphenylmethane.

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.

Steric Factor and Activation Energy of the Reaction Na+C2H5Cl = NaCl+C2H5

1952 ◽  
Vol 20 (6) ◽  
pp. 1016-1020 ◽  
Author(s):  
R. J. Cvetanović ◽  
D. J. Le Roy
Keyword(s):  
Activation Energy ◽  
Steric Factor

THE STERIC FACTOR IN THE HYDROLYSIS OF β-1,4′-OLIGOGLUCOSIDES BY MYROTHECIUM CELLULASE

1956 ◽  
Vol 34 (1) ◽  
pp. 102-115 ◽  
Author(s):  
D. R. Whitaker
Keyword(s):  
Activation Energy ◽  
Rate Constant ◽  
Rate Constants ◽  
Activation Energies ◽  
Enzymic Activity ◽  
Degree Of Polymerization ◽  
Steric Factor ◽  
Collision Theory ◽  
Hydrolysis Of

A comparison of the rate constants and activation energies for the hydrolysis of cellobiose, cellotriose, cellotetraose, and cellopentaose by Myrothecium cellulase showed that while the rate constant was increased by a factor of about 450 as the degree of polymerization (D.P.) of the substrate was increased from two to five, the activation energy remained at about 12,000 cal. The results are interpreted, in terms of classical collision theory, as indicating that the increase in rate constant with D.P. is determined by an increase in the steric factor with D.P. Addition of a β-linked sorbityl group to an oligoglucoside increased the rate constant; the increase was less than that from addition of an anhydroglucose unit and, relative to the latter, diminished as the D.P. of the chain undergoing addition was increased. Exposing the enzyme to conditions favoring thermal or surface denaturation caused varying losses in enzymic activity towards the four oligoglucosides; wherever the loss in activity towards one oligoglucoside differed substantially from the loss in activity towards any other oligoglucoside, the greater loss was shown towards the substrate of lower D.P. The results are discussed.

Adsorption and Decomposition of Trimethylarsenic on GaAs(100)

1988 ◽  
Vol 131 ◽  
Author(s):  
J. R. Creighton
Keyword(s):  
Activation Energy ◽  
Electron Irradiation ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Temperature Programmed Desorption ◽  
Methyl Radicals ◽  
Arsenic Compounds ◽  
Group V ◽  
Desorption Activation Energy ◽  
Temperature Programmed

ABSTRACTAlkylated arsenic compounds have shown some promise as alternatives to arsine as the group-V source gas for GaAs MOCVD. However, little is known about the fundamental chemical interactions of these compounds with the GaAs surface. We have investigated the adsorption and reactivity of trimethylarsenic (TMAs) on GaAs(100) using temperature programmed desorption (TPD), Auger electron spectroscopy, and LEED. For the exposures and temperatures studied, TMAs did not pyrolytically decompose on the GaAs(100). TPD results indicate that TMAs chemisorbs, apparently non-dissociatively, and desorbs ≅330 K. Multilayers of TMAs desorb ≅140–160 K. Exposure of adsorbed TMAs to 70 eV electrons results in irreversible decomposition of the molecule. After electron irradiation, TPD shows that methyl radicals desorb at 660 K, which corresponds to a desorption activation energy of ≅40 kcal/mol. At higher temperatures, As2, H2, C2H2, and a smaller amount of methyl radicals desorb, and a small coverage of carbon remains on the surface.

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