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 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 REACTION OF ACTIVE NITROGEN WITH ETHANOL

1965 ◽  
Vol 43 (4) ◽  
pp. 935-939 ◽  
Author(s):  
P. A. Gartaganis
Keyword(s):  
Flow System ◽  
Methyl Radicals ◽  
Kcal Mole ◽  
Hydrogen Atoms ◽  
Active Nitrogen ◽  
Condensed Discharge ◽  
Preliminary Study ◽  
Fast Flow ◽  
Ethyl Radicals ◽  
Water Hydrogen

The reaction of active nitrogen with ethanol has been investigated in the range 300 to 593 °K using a modified condensed-discharge Wood–Bonhoeffer fast-flow system. The only condensable products found in appreciable amounts were hydrogen cyanide and water. Hydrogen was the main noncondensable product. A very small amount of acetaldehyde was also formed along with traces of ethane, ethylene, methane, acetonitrile, cyanogen, and probably carbon monoxide. The overall activation energy is 3.4 kcal/mole. It is postulated that the mechanism consists of the formation of two fragments NC2H5 and OH, from which the condensable products result as follows:[Formula: see text]A number of products found in trace quantities are produced by concomitant reactions of the hydrogen atoms with methyl radicals, and with ethanol as well as by disproportionation of ethyl radicals to produce ethane and ethylene. A preliminary study of the reaction of active nitrogen with isopropanol indicated that the energy of activation is in line with the energies of activation of methanol and ethanol.

THE REACTION OF HYDROGEN ATOMS WITH METHYL CYANIDE

1955 ◽  
Vol 33 (12) ◽  
pp. 1814-1818 ◽  
Author(s):  
W. Forst ◽  
C. A. Winkler
Keyword(s):  
Discharge Tube ◽  
Hydrogen Cyanide ◽  
Main Product ◽  
Initial Step ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Methyl Cyanide ◽  
Secondary Reactions

Hydrogen atoms produced in a discharge tube were found to react with methyl cyanide to produce hydrogen cyanide as the main product, together with smaller amounts of methane and ethane. The proposed mechanism involves the formation of hydrogen cyanide and a methyl radical in the initial step; methane and ethane are attributed to secondary reactions of the methyl radicals.

The kinetics of the interaction of atomic hydrogen with olefines. V. Results obtained for a further series of compounds

1950 ◽  
Vol 202 (1069) ◽  
pp. 181-202 ◽  
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Atomic Hydrogen ◽  
Methyl Radicals ◽  
Hydrogen Atoms ◽  
Alkyl Radicals ◽  
Kinetics Of ◽  
Interesting Generalization

In this paper the efficiency of interaction of a hydrogen atom with a series of olefines has been determined, the olefines being members of the series obtained by progressively replacing the hydrogen atoms of ethylene by methyl radicals. The interesting generalization which emerges from this is that the efficiency of interaction does not vary very much with the nature of the alkyl substituents in the molecule, and calculations involving the heats of addition of a hydrogen atom to a double bond confirm this generalization. The data presented here are discussed critically in relation to information available on the reaction of CCl 3 radicals with olefines and of alkyl radicals with olefines, complete general agreement being demonstrated.

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.

Radiolysis of methylcyclohexane. III. Pure vapor phase and effects of additives

1967 ◽  
Vol 45 (14) ◽  
pp. 1649-1659 ◽  
Author(s):  
W. J. Holtslander ◽  
G. R. Freeman
Keyword(s):  
Vapor Phase ◽  
Secondary Reaction ◽  
Hydrogen Yield ◽  
Methyl Radicals ◽  
Hydrogen Atoms ◽  
Hydrogen Formation ◽  
Positive Ions ◽  
Total Ionization ◽  
Different Types ◽  
Increasing Temperature

The radiolysis of methylcyclohexene (MCH) vapor was carried out under a variety of conditions. The G-values of the main products at 110°, extrapolated to zero dose, are hydrogen (5.2), methylcyclohexene isomers (2.0), ethylene (1.5), methane (1.3), propylene (0.8), and total dimer (0.3). Other products were also measured.The hydrogen yield was reduced to G = 3.1 by each of the additives, N2O, SF6, and CCL4, and to G = 1.6 by C2H4. Both DI and ND3 increased the total hydrogen yield above the value in pure MCH. In pure MCH approximately 50% of the ions (G(total ionization) = 4.4) resulted in hydrogen formation, whereas in the presence of DI or ND3, 75% of the ions are hydrogen precursors. Thus three different types of positive ions are distinguished in the system: G(M1+) = 2.1, G(M2+) = 1.3, and G(N+) = 1.0.The average ion lifetime with respect to neutralization was 10−3 s. The ion DI−was therefore stable with respect to decomposition to D + I− for a period greater than 10–3 s under the conditions of the experiments (~380 Torr MCH, 110°).The yield of methylcyclohexene isomers increased with increasing temperature and increased upon addition of ND3 or C2H4 to the radiolysis system. The dimer yield was also enhanced by the addition of ND3. This effect was explained by the occurrence of an ionic secondary reaction that destroys methylcyclohexene and (or) methylcyclohexyl radicals in pure MCH.Approximately 85% of the methane is produced by methyl radicals abstracting hydrogen atoms from MCH.

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