Hydrogen Abstraction from Methyl Formate by Methyl Radicals

1971 ◽  
Vol 49 (6) ◽  
pp. 828-832 ◽  
Author(s):  
T. R. Donovan ◽  
W. Dorko ◽  
A. G. Harrison
Keyword(s):  
Methyl Formate ◽  
Hydrogen Abstraction ◽  
Methyl Radicals ◽  
Arrhenius Parameters

The reactions of CH3 radicals with methyl formate and CD3 radicals with methyl formate and methyl formate-d have been studied. The CH3 and CD3 radicals were produced by the photolysis of acetone and acetone-d. The Arrhenius parameters (log A, A in 1 mol−1 s−1; E, in kcal mol−1) for hydrogen abstraction are as follows[Formula: see text]

Reactions of methyl radicals. V. Hydrogen abstraction from hydrogen sulfide

1983 ◽  
Vol 36 (11) ◽  
pp. 2195 ◽  
Author(s):  
H Arican ◽  
NL Arthur
Keyword(s):  
Hydrogen Sulfide ◽  
Rate Constant ◽  
Hydrogen Abstraction ◽  
Methyl Radicals ◽  
Arrhenius Parameters ◽  
Temperature Range

Hydrogen abstraction from H2S by CH3 radicals, produced by the photolysis of azomethane, has been studied in the temperature range 334-432 K. The rate constant, based on the value 1013.34 cm3 mol-1 s-1 for the recombination of CH3 radicals, is given by log k4 = (11.00 � 0.01) - (8760 � 80)/19.145T where k4 is in cm3 mol-1 s-1 and E is in J mol-1. The previous data reported for this reaction are discussed and best values for its Arrhenius parameters are recommended. The results indicate that CH3 radicals react faster than CF3 radicals with H2S; this confirms the importance of polar effects in the hydrogen abstraction reactions of CF3 radicals.

Reactions of methyl radicals. IV. Hydrogen abstraction from tetramethylsilane by methyl radicals produced by the photolysis of both acetone and azomethane

1983 ◽  
Vol 36 (11) ◽  
pp. 2185 ◽  
Author(s):  
H Arican ◽  
NL Arthur
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Negligible Effect ◽  
Experimental Temperature ◽  
Methyl Radicals ◽  
Arrhenius Parameters ◽  
Temperature Ranges ◽  
Reported Data

Studies of hydrogen abstraction by CH3 radicals from (CH3),Si with two different radical sources, acetone and azomethane, have yielded data on the reactions CH3 + Ch3COCH3 → CH4 + CH3COCH2 (1) CH3 + CH3NNCH3 → CH4 + CH3 NNCH2 (2) Ch3 + (Ch3)4Si → Ch4 + (CH3)3SiCH2 Their rate constants, based on the value of 1013.34 cm3 mol-1 s-1 for the recombination of CH3 radicals, together with the corresponding experimental temperature ranges, are given by (k in cm3 mol-1 s-1, E in J mol-1): log k2 = (11.54±0.02) - (40 000±220)/19.145T 398-522 K (2) log k8 = (10.98±0.02) - (32 550±160)/19.145T 334-463 K (8) log k8' = (11.03±0.02) - (32 920±180)/19.145T (8') With acetone as the radical source: log k5 = (11.85±0.06) - (44 810±160)/19.145T 395-523 K (5) With azomethane as the radical source: log ks = (11.88±0.03) - (44 610±260)/19.145T 363-463 K (5) log k5' = (12.02±0.04) - (45 630±310)/19.145T (5') where k5' and k5' are the values for ks and k5, respectively, obtained after allowance is made for the formation of C2H6 by way of the intramolecular decomposition of azomethane. From a consideration of these and previously reported data on CH3 and CD3 attack on (CH3)4Si, we conclude that the source of CH3 radicals, and the intramolecular formation of C2H6 in the photolysis of azomethane, both have a negligible effect on the rate constants for the reaction, and that CH3 and CD3 radicals are of equal reactivity. We also recommend best values for the Arrhenius parameters for the reaction.

Hydrogen abstraction by methyl radicals in glasses

1984 ◽  
Vol 78 ◽  
pp. 175 ◽  
Author(s):  
Takahisa Doba ◽  
Keith U. Ingold ◽  
Willem Siebrand ◽  
Timothy A. Wildman
Keyword(s):  
Hydrogen Abstraction ◽  
Methyl Radicals

Photolysis (λ =185 nm) of Liquid Pivalaldehyde Dimethyl Aceta

1977 ◽  
Vol 32 (2) ◽  
pp. 209-212 ◽  
Author(s):  
Peter Naderwitz ◽  
Heinz-Peter Schuchmann ◽  
Clemens Von Sonntag
Keyword(s):  
Methyl Formate ◽  
Hydrogen Abstraction ◽  
Dimethyl Acetal ◽  
Quantum Yields ◽  
Formaldehyde Dimethyl Acetal

Deoxygenated liquid pivalaldehyde dimethyl acetal was photolyzed at λ = 185 nm, and 28 products have been determined. The major ones and their quantum yields are: methyl formate (0.47), isobutene (0.39), methane (0.28), neopentane (0.16), isobutane (0.13), formaldehyde dimethyl acetal (0.13), formaldehyde (0.09), methyl neopentyl ether (0.09), methanol (0.07), and methyl pivalate (0.04). The predominant primary photoprocesses are suggested to be the scission of the O–CH3 bond (homolytic, 0.51; molecular, 0.04) and the C-tBu bond (homolytic and molecular, 0.16). Minor processes are the scission of the C–OCH3 (molecular, 0.09; homolytic, 0.03), C–H (0.006), and C–CH3 bonds (< 0.01). The radical (A) eliminates with ease t-butyl (reaction (i)). This process is at least 10 times more efficient than methoxy elimination or hydrogen abstraction from the substrate.[xxx]

The homogeneous conversion of methane to higher hydrocarbons in the presence of ethylene in the temperature range 925–1023 K

1991 ◽  
Vol 69 (1) ◽  
pp. 37-42 ◽  
Author(s):  
Alain R. Bossard ◽  
Margaret H. Back
Keyword(s):  
Hydrogen Abstraction ◽  
Homogeneous System ◽  
Catalytic Reactions ◽  
The Other ◽  
Methyl Radicals ◽  
Temperature Range ◽  
Vinyl Radicals ◽  
Conversion Of Methane ◽  
Radical Distribution ◽  
Higher Hydrocarbons

Mixtures of ethylene and methane have been pyrolyzed in the temperature range 925–1023 K for the purpose of converting methane to higher hydrocarbons. Addition of methane to thermally-reacting ethylene increases the rate of formation of propylene but decreases the rates of formation of the other major products, ethane, acetylene, and butadiene. Hydrogen abstraction from methane is a major propagation reaction and causes a shift in the radical distribution from ethyl and vinyl radicals, the main radicals in the pyrolysis reactions of ethylene alone, to methyl radicals, which lead to the formation of propylene. At 1023 K with a pressure of ethylene of 6.5 Torr and of methane of 356 Torr, 1.5 mol of methane is converted to higher molecular weight products for every mole of ethylene reacted. The rate of conversion of methane in the homogeneous system is lower than in catalytic reactions but the product is entirely hydrocarbon and no methane is lost to carbon monoxide or carbon dioxide. Key words: methane, ethylene, kinetics, pyrolysis, fuels.

Kinetics of radical exchange in the reaction of CF3 radicals with tin tetramethyl

1976 ◽  
Vol 54 (10) ◽  
pp. 1617-1623 ◽  
Author(s):  
T. N. Bell ◽  
P. J. Young
Keyword(s):  
Exchange Reaction ◽  
Rate Constant ◽  
Additional Data ◽  
Hydrogen Abstraction ◽  
Arrhenius Parameters ◽  
Abstraction Reaction ◽  
Reaction Proceeds ◽  
Kinetics Of

The reaction of CF3 radicals with SnMe4 leads to hydrogen abstraction and also radical exchange.[Formula: see text]We propose the exchange reaction proceeds via a five coordinate intermediate. The Arrhenius parameters for the exchange reaction are,[Formula: see text]Additional data for the H abstraction reaction[Formula: see text]combined with previous data yields an improved rate constant for abstraction,[Formula: see text]

THE REACTIONS OF TRIFLUOROMETHYL RADICALS WITH PROPANE, n-BUTANE, AND ISOBUTANE

1956 ◽  
Vol 34 (2) ◽  
pp. 103-107 ◽  
Author(s):  
P. B. Ayscough ◽  
E. W. R. Steacie
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Methyl Radicals ◽  
Kcal Mole

A study of the reactions of trifluoromethyl radicals, produced by the photolysis of hexafluoroacetone, with propane, n-butane, and isobutane has been made. The rate constants of the hydrogen-abstraction reactions have been determined at temperatures between 27 °C and 119 °C and the activation energies found to be 6.5 ± 0.5, 5.1 ± 0.3, and 4.7 ± 0.3 kcal./mole respectively. These values are compared with those obtained for the reactions with methane and ethane, and with the corresponding reactions of methyl radicals.

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