Trapped hydrogen atoms, deuterium atoms, and methyl radicals in methane and methane-d4 at 5-50 K. Yields from photolysis of HX and from radiolysis; decay mechanisms; reactions with oxygen and carbon monoxide

1981 ◽  
Vol 85 (10) ◽  
pp. 1310-1323 ◽  
Author(s):  
Debasis Bhattacharya ◽  
Hsien-Yien Wang ◽  
John E. Willard
Keyword(s):  
Carbon Monoxide ◽  
Methyl Radicals ◽  
Hydrogen Atoms

Primary process(es) in the mercury-photosensitized decomposition of dimethyl ether at 2537 Å

1968 ◽  
Vol 46 (16) ◽  
pp. 2693-2697 ◽  
Author(s):  
R. Payette ◽  
M. Bertrand ◽  
Y. Rousseau
Keyword(s):  
Carbon Monoxide ◽  
Quantum Yield ◽  
Light Intensity ◽  
Dimethyl Ether ◽  
Molecular Hydrogen ◽  
Room Temperature ◽  
Primary Process ◽  
Methyl Radicals ◽  
Hydrogen Atoms ◽  
Radical Recombination

The mercury-photosensitized decomposition of dimethyl ether has been studied at room temperature and at pressures ranging from 10 to 200 Torr.The formation of an excited dimethyl ether (DME) molecule has been verified by following the rates of formation of methane, ethane, and carbon monoxide with various ether pressures.The study of the variation of the quantum yield of molecular hydrogen formation with absorbed light intensity at high ether pressures has shown that the primary process involves the dissociation of ether molecules into hydrogen atoms and methoxy methyl radicals:[Formula: see text]The results presented in this paper indicate that the excited DME molecule can originate in a radical recombination between hydrogen atoms and methoxy methyl radicals.

THE PHOTOLYSIS OF DEUTERATED ACETONE AND OF DEUTERATED ACETONE–HYDROGEN MIXTURES

1960 ◽  
Vol 38 (11) ◽  
pp. 2161-2170 ◽  
Author(s):  
J. F. Henderson ◽  
E. W. R. Steacie
Keyword(s):  
Carbon Monoxide ◽  
Excited Molecule ◽  
Methyl Radicals ◽  
Hydrogen Mixtures

The photolyses of acetone, acetone-d6, and acetone-d6 – hydrogen mixtures were investigated at 471 °K. The rates of formation of methane, ethane, and carbon monoxide and the ratio [Formula: see text] were independent of the fractional amount of acetone which photolyzed, as measured by 100[CO]/[A]0, which was varied from <1% to 18%. When the acetone-d6–hydrogen mixtures were photolyzed, [Formula: see text] and [Formula: see text] were observed to be functions of [A]0 and [H2]0. It is postulated that some of the CD4 and CD3H was formed by a reaction between methyl radicals and an excited molecule which contained both C—D and C—H bonds.

Reactions of free radicals with aromatic compounds in the gaseous phase. I. Kinetics of the reaction of methyl radicals with toluene

1964 ◽  
Vol 17 (12) ◽  
pp. 1329 ◽  
Author(s):  
MFR Mulcahy ◽  
DJ Williams ◽  
JR Wilmshurst
Keyword(s):  
Flow System ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Methyl Group ◽  
Benzyl Radical ◽  
Toluene Molecule ◽  
Benzyl Radicals ◽  
Butyl Peroxide ◽  
Kinetics Of

The kinetics of abstraction of hydrogen atoms from the methyl group of the toluene molecule by methyl radicals at 430-540�K have been determined. The methyl radicals were produced by pyrolysis of di-t-butyl peroxide in a stirred-flow system. The kinetics ,agree substantially with those obtained by previous authors using photolytic methods for generating the methyl radicals. At toluene and methyl-radical concentrations of about 5 x 10-7 and 10-11 mole cm-3 respectively the benzyl radicals resulting from the abstraction disappear almost entirely by combination with methyl radicals at the methylenic position. In this respect the benzyl radical behaves differently from the iso-electronic phenoxy radical, which previous work has shown to combine with a methyl radical mainly at ring positions. The investigation illustrates the application of stirred-flow technique to the study of the kinetics of free-radical reactions.

The reaction of hydrogen atoms with ethylene

1970 ◽  
Vol 316 (1527) ◽  
pp. 575-591 ◽  
Keyword(s):  
Hydrogen Atom ◽  
Rate Constant ◽  
Recombination Reaction ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Ethyl Radical ◽  
Cracking Reaction ◽  
Computer Calculations ◽  
First Time

A detailed study has been made of the products from the reaction between hydrogen atoms and ethylene in a discharge-flow system at 290 ± 3 K. Total pressures in the range 8 to 16 Torr (1100 to 2200 Nm -2 ) of argon were used and the hydrogen atom and ethylene flow rates were in the ranges 5 to 10 and 0 to 20 μ mol s -1 , respectively. In agreement with previous work, the main products are methane and ethane ( ~ 95%) together with small amounts of propane and n -butane, measurements of which are reported for the first time. A detailed mechanism leading to formation of all the products is proposed. It is shown that the predominant source of ethane is the recombination of two methyl radicals, the rate of recombination of a hydrogen atom with an ethyl radical being negligible in comparison with the alternative, cracking reaction which produces two methyl radicals. A set of rate constants for the elementary steps in this mechanism has been derived with the aid of computer calculations, which gives an excellent fit with the experimental results. In this set, the values of the rate constant for the addition of a hydrogen atom to ethylene are at the low end of the range of previously measured values but are shown to lead to a more reasonable value for the rate constant of the cracking reaction of a hydrogen atom with an ethyl radical. It is shown that the recombination reaction of a hydrogen atom with a methyl radical, the source of methane, is close to its third-order region.

The Reactions of Methyl Radicals. III. The Abstraction of Hydrogen Atoms from Olefins

1951 ◽  
Vol 19 (2) ◽  
pp. 169-171 ◽  
Author(s):  
A. F. Trotman‐Dickenson ◽  
E. W. R. Steacie
Keyword(s):  
Methyl Radicals ◽  
Hydrogen Atoms

Reactions of carbon with atomic gases

1959 ◽  
Vol 12 (4) ◽  
pp. 533 ◽  
Author(s):  
JD Blackwood ◽  
FK McTaggart
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Water Vapour ◽  
Active Sites ◽  
Atmospheric Temperature ◽  
Carbon Surface ◽  
Hydrogen Atoms ◽  
Different Temperatures ◽  
Atomic Species ◽  
Oxygen Groups

Wood chars were reacted at atmospheric temperature with hydrogen atoms, oxygen atoms and carbon monoxide, hydrogen atoms and hydroxyl radicals, produced by the action of a radio frequency field on hydrogen, carbon dioxide, and water vapour respectively. The chars were prepared at different temperatures and contained different amounts of oxygen. The experimental results showed that the gases must be present in the atomic form before reaction with the carbon can take place and that such species react on the carbon-surface independently of active sites. In normal gasification processes the atomic species appear to be produced at active centres, which for the chars used could be correlated with specific oxygen groups remaining in the carbon. It is suggested that these groupings may have a pyran structure. An explanation has been put forward for the retardation of the carbon-water vapour reaction by hydrogen, and of the carbon-carbon dioxide reaction by carbon monoxide. These are considered as due to reverse mechanisms which decrease the concentration of the atomic species and not to the blocking of active sites by adsorption of the retardant.

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