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. I. Hydrogen abstraction from dimethyl sulphide

1976 ◽  
Vol 29 (7) ◽  
pp. 1483 ◽  
Author(s):  
NL Arthur ◽  
M Lee
Keyword(s):  
Free Radicals ◽  
Rate Constant ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Reverse Reaction ◽  
Thermochemical Data ◽  
Methyl Radicals ◽  
Dimethyl Sulphide ◽  
Temperature Range

Hydrogen abstraction from (CH3),S and CH3COCH3 by CH3 radicals CH3+CH3SCH3 → CH4+CH3SCH2 CH3 + CH3COCH3 → CH4 + CH3COCH2 has been studied in the temperature range 120-245�. The rate constants, based on the value of 1013.34cm3 mol-l s-1 for the recombination of CH3 radicals, are given by (k in cm3 mol-1 s-1, E in kJ mol-1, R = 0.008314 kJ K-1 mol-1): logk1 = (11.62 � 0.08) ? (38.35 � 0.68)/2.303RT logk3 = (11.61 � 0.05) ? (40.48 � 0.46)/2.303RT Combination of the results for (1) with thermochemical data gives a calculated value of Logk-1 = (11.8 -63.7/2.303RT for the rate constant of the reverse reaction. The results for CH3+(CH3)2S are compared with all of the available data for hydrogen abstraction by free radicals from both sulphur-containing compounds, and molecules of the type (CH3)xM.

Reactions of trifluoromethyl radicals. I. Hydrogen abstraction from dimethyl sulphide

1972 ◽  
Vol 25 (4) ◽  
pp. 803 ◽  
Author(s):  
NL Arthur ◽  
KS Yeo
Keyword(s):  
Hydrogen Atom ◽  
Rate Constant ◽  
Hydrogen Abstraction ◽  
Reverse Reaction ◽  
Thermochemical Data ◽  
Hydrogen Atom Abstraction ◽  
Dimethyl Sulphide ◽  
Temperature Range

Hydrogen atom abstraction from (CH3)2S by CF3 radicals has been studied in the temperature range 79-167�: (1) CF3 + CH3SCH3 ←→ CF3H + CH3SCH2 (-1) The rate constant, based on Ayscough's value of 1013.36cmS mol-l s-l for the recombination of CF3 radicals, is given by (k1 in cm3 mol-1 s-l, E in J mol-l): Logk1 = (12.05 � 0.02)-(28710 � 130)/2.303RT Combination of these results with thermochemical data gives a calculated value of log k-1 = 12.2 - 62600/2.303RT for the rate constant of the reverse reaction. ΔH�f(CH3SCH2) and S�(CH3SCH2) are estimated to be 155.6 kJ mol-l and 290 J K-l mol-1 respectively.

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]

Reactions of trifluoromethyl radicals. II. Hydrogen abstraction from monochlorosilane

1973 ◽  
Vol 26 (6) ◽  
pp. 1269 ◽  
Author(s):  
NL Arthur ◽  
BR Harman
Keyword(s):  
Hydrogen Atom ◽  
Rate Constant ◽  
Experimental Error ◽  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Hydrogen Atom Abstraction ◽  
Temperature Range ◽  
Average Value

Hydrogen atom abstraction from SiH3Cl by CF3 radicals ����������������� CF3 + SiH3Cl → CF3H+SiH2Cl������������������� (1) has been studied in the temperature range 69-168�. The rate constant, based on Ayscough's value of 1013.36 cm3 mol-1 s-1 for the recombination of CF3 radicals, is given by (k1 in cm3 mol-1 s-1, E in kJ mol-1): ������������������ logk1 = (12.38�0.06)-(25.72�0.41)/2.303RT At 400 K, the rate constant for CF3 + SiH3Cl is greater than the average value reported for CF3+SiHCl3 by a factor of 3.6. This is due to a difference in A factors since the activation energies are equal within experimental error.

The Rate-Constant for the Recombination of Methyl Radicals

1986 ◽  
Vol 39 (8) ◽  
pp. 1257 ◽  
Author(s):  
NL Arthur ◽  
JC Biordi
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Rate Constant ◽  
Rate Constants ◽  
The Other ◽  
Methyl Radicals ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Best Value ◽  
Limiting Value

Rate constants for the recombination of CH3 radicals have been measured by means of the rotating sector technique in the temperature range 373- 463 K, and at a pressure of 30 Torr . CH3 radicals were produced by the photolysis of acetone, and the experimental data were fitted to sector curves generated from Shepp's theory. The results give kb = (2.81�0.22)×1013 cm3 mol-1 s-1, which, under the chosen experimental conditions, is close to its high-pressure limiting value. A comparison is made with the other values of the rate constant reported in the literature, and a best value is suggested.

Reactions of Methyl Radicals. II. Hydrogen Abstraction from Methyl Trifluoroacetate

1979 ◽  
Vol 32 (5) ◽  
pp. 1025 ◽  
Author(s):  
NL Arthur ◽  
PJ Newitt
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Methyl Radicals ◽  
Temperature Range ◽  
Cf3 Radical

Hydrogen abstraction from CF3COOCH3 and CH3COCH3 by CH3 radicals CF3 + CF3COOCH3 → CH4 + CF3COOCH2 (1) CF3 + CF3COOCH3 → CH4 + CH3COCH2 (3) has been studied in the temperature range 117-244�. The rate constants, based on the value of 1013.34 cm3 mol-1 s-1 for the recombination of CH3 radicals, are given by (k in cm3 mol-1 s-1 and E in J mol-1) : logk1 = (10.39 � 0.11)- (37680 � 880)/19.145T logk3 = (11.53 � 0.02)- (40590 � 170)/19.145T CF3COOCH3 is less susceptible to attack by CH3 radicals than by CF3 radicals by a factor of 2.8 at 400 K, due mainly to a difference in A factors, since the activation energies of the two reactions are almost identical. These results can be rationalized in terms of intermolecular polar repulsion between the CF3 radical and CF3COOCH3.

Reactions of Methyl Radicals. III. Hydrogen Abstraction from Methyl Acetate and Methyl [2H3]Acetate

1979 ◽  
Vol 32 (8) ◽  
pp. 1697 ◽  
Author(s):  
NL Arthur ◽  
PJ Newitt
Keyword(s):  
Isotope Effect ◽  
Rate Constants ◽  
Methoxy Group ◽  
Methyl Acetate ◽  
Kinetic Isotope Effect ◽  
Hydrogen Abstraction ◽  
Methyl Radicals ◽  
Temperature Range ◽  
Kinetic Isotope ◽  
Acetyl Group

A study of hydrogen abstraction by CH3 radicals from CH3COOCH3 in the temperature range 116-224°, and from CD3COOCH3 in the range 117-234°, has yielded data on the reactions: CH3 + CH3COOCH3 → CH4 + [C3H5O2] (4) CH3 + CH3COOCH3 → CH4 + CH2COOCH3 (5) CH3 + CH3COOCH3 → CH4 + CH3COOCH2 (6) CH3 + CD3COOCH3 → CH3D + CD2COOCH3 (7) The corresponding rate constants, based dn the value of 1013.34 cm3 mol-1 s-1 for the recombination of CH3 radicals, are given by (k in cm3 mol-1 s-1 and E in J mol-1): logk4 = (11.56 ± 0.12) - (44430 ± 970)/19.145T (4) logk5 = (11.17 ± 0.22) - (42900 ± 1760)/19.145T (5) logk6 = (11.44 ± 0.16) - (46980 ± 1290)/19.145T (6) logk7 = (11.39 ± 0.04) - (52110 ± 330)/19.145T (7) At 400 K, 64% of abstraction occurs from the acetyl group, and 36% from the methoxy group. The kinetic isotope effect at 400 K for attack on the acetyl group is 9.6; this is mainly due to a difference in activation energies since the quotient of A factors is close to unity.

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]

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