Two mechanisms for formation of methyl radicals during the thermal decomposition of methyl iodide on a copper surface

1993 ◽  
Vol 97 (38) ◽  
pp. 9713-9718 ◽  
Author(s):  
Jong Liang Lin ◽  
Brian E. Bent
Keyword(s):  
Thermal Decomposition ◽  
Methyl Iodide ◽  
Copper Surface ◽  
Methyl Radicals

High Temperature Absorption of the 3.39 µm He-Ne Laser Line by Small Hydrocarbons

1978 ◽  
Vol 32 (5) ◽  
pp. 489-493 ◽  
Author(s):  
D. B. Olson ◽  
W. G. Mallard ◽  
W. C. Gardiner
Keyword(s):  
High Temperature ◽  
Temperature Dependence ◽  
Methyl Iodide ◽  
Transient Absorption ◽  
Broad Band ◽  
Laser Line ◽  
Methyl Radicals ◽  
Large Numbers ◽  
Absorbing States ◽  
No Absorption

Absorptivity measurements for the 3.39 µm He-Ne laser line are reported for methane, acetylene, ethylene, ethane, propane, n-butane, and n-pentane over the temperature range 300 < T < 2000°K. Shock-heated mixtures containing formaldehyde and methyl iodide showed no absorption or transient absorption at any temperature that could be attributed to formaldehyde or methyl radicals. The temperature dependence of the absorptivities of the C2 and higher hydrocarbons was much weaker than for methane. Comparison with simple theoretical expectations and broad-band absorptivities showed that the higher hydrocarbon absorptions include quite large numbers of absorbing states.

The Kinetics of the Thermal Decomposition of Gaseous Methyl Iodide

1935 ◽  
Vol 57 (3) ◽  
pp. 488-488
Author(s):  
E. W. R. Steacie ◽  
R. D. McDonald
Keyword(s):  
Thermal Decomposition ◽  
Methyl Iodide ◽  
Kinetics Of

Moderation of Hot Methyl Radicals in Photolysis of Methyl Iodide

1953 ◽  
Vol 21 (10) ◽  
pp. 1894-1894 ◽  
Author(s):  
Frank P. Hudson ◽  
Russell R. Williams ◽  
William H. Hamill
Keyword(s):  
Methyl Iodide ◽  
Methyl Radicals

scholarly journals Generation of Ketene With High Quantum Yield by a KrF Laser

1985 ◽  
Vol 5 (5) ◽  
pp. 257-273 ◽  
Author(s):  
Zhang Yunwu ◽  
W. Fuss ◽  
K. L. Kompa ◽  
F. Rebentrost
Keyword(s):  
Thermal Decomposition ◽  
Single Step ◽  
Quantum Yields ◽  
Methyl Radicals ◽  
High Quantum ◽  
Photochemical Formation ◽  
A Chain ◽  
Technical Interest ◽  
Approximate Rate ◽  
Pulsed Laser Irradiation

Acetone was photolyzed around 770 K by pulsed laser irradiation at 248 nm. The methyl radicals, generated in the primary step, trigger a chain reaction, producing ketene (CH2CO) and methane. Long chains (high quantum yields) result from low radical concentrations. Using a collimated laser beam of low intensity, quantum yields up to 300 have been demonstrated. Approximate rate constants have been derived and used for extrapolation to higher temperatures and different densities. Compared to the thermal process, the photochemical formation of ketene is faster. Therefore its thermal decomposition can be avoided to some extent. But the improvement is probably too small to be of technical interest. We also found indications that the thermal decomposition of acetone above about 500 to 600 K yields three fragments in a single step.

Estimation of the individual rate constants for the steps in the thermal decomposition of ethane

1963 ◽  
Vol 271 (1344) ◽  
pp. 34-43 ◽  
Keyword(s):  
Thermal Decomposition ◽  
Rate Constants ◽  
General Pattern ◽  
Reaction Scheme ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Pattern Of Variation ◽  
The Individual ◽  
Limiting Case ◽  
Individual Rate

A reaction scheme analogous to that used for the higher paraffins (Blackmore & Hinshelwood 1962 b ) is tested for its applicability to the thermal decomposition of ethane and its inhibition by nitric oxide. Ethane constitutes a limiting case for the paraffin series, in that Hatomsre ­place methyl radicals as chain-carrying species. The individual rate constants of the reaction steps are estimated on the basis of this scheme, and will all conform satisfactorily to the general pattern of variation in the homologous series, allowance being made for the discontinuous increase expected when an H atom appears instead of a methyl radical.

Elementary reactions in the photochemical oxidation of methyl iodide

1958 ◽  
Vol 244 (1238) ◽  
pp. 411-423 ◽  
Keyword(s):  
Methyl Iodide ◽  
Relative Rate ◽  
Molecular Iodine ◽  
Photochemical Oxidation ◽  
Main Reaction ◽  
Methyl Radicals ◽  
Iodine Molecule ◽  
Methyl Radical ◽  
Elementary Reactions ◽  
Molecule Reaction

The photochemical oxidation of gaseous methyl iodide at room temperature was investigated under conditions such that oxygen molecules were competing with iodine molecules and/or iodine atoms for reaction with methyl radicals. The molecular iodine produced in the oxidation was measured by means of its light absorption. A balanced photomultiplier system for the determination of small percentage light absorptions is described. Analysis of the results shows that the contribution of the methyl radical + iodine atom recombination is negligible compared with the methyl radical + iodine molecule reaction for the relative concentrations of iodine atoms and iodine molecules involved. The variation with pressure of the ratio of the rate constant of the methyl radical + iodine molecule reaction to that of the methyl radical + oxygen molecule reaction indicates that the main reaction of methyl radicals with oxygen is a third-order one. This is assumed to be their association to form methylperoxy radicals. Methyl iodide is approximately ten times as efficient as carbon dioxide in acting as a third body for this association. The relative rate of a simultaneous second-order reaction of methyl radicals with oxygen has also been determined. From comparison with other work, the probable orders of magnitude of the rate constants of these elementary reactions of the methyl radical are deduced.

Chemistry of pyrrolic compounds. XXVII. Some aspects of the mass spectra and chemistry of meso-substituted porphyrins

1974 ◽  
Vol 27 (5) ◽  
pp. 1103 ◽  
Author(s):  
PS Clezy ◽  
Cl Lim ◽  
JS Shannon
Keyword(s):  
Thermal Decomposition ◽  
Mass Spectrometer ◽  
Mass Spectra ◽  
Side Chains ◽  
Methyl Radicals ◽  
Porphyrin Derivative ◽  
Acetic Ester ◽  
Hydrolysis Of ◽  
Successive Loss

Characteristic fragmentations have been observed in the mass spectra of some meso-substituted porphyrins, and especially in some meso-oxy derivatives. meso-Substituted octaethylporphyrins generally underwent thermal decomposition in the mass spectrometer; this resulted in the formation of the parent porphyrin from which the successive loss of eight methyl radicals was observed. Attempts to prepare meso-carboxyoctaethylporphyrin by oxidation of the formyl derivative or by hydrolysis of the meso-cyano compound failed. As a by-product of the preparation of meso-cyano- octaethylporphyrin a porphyrin isocyanide was obtained. Some aspects of the chemistry of this novel porphyrin derivative are reported together with the preparation and properties of an oxyporphyrin substituted with acetic ester side chains.

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