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.

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.

Reactions of trifluoromethyl radicals. VI. Hydrogen abstraction from trifluoroacetic acid and trifluoroacetic (2H1)acid

1981 ◽  
Vol 34 (7) ◽  
pp. 1535 ◽  
Author(s):  
NL Arthur ◽  
LF David
Keyword(s):  
Trifluoroacetic Acid ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Temperature Ranges

The hydrogen abstraction reactions of CF3 radicals with CF3COOH and CF3COOD CF3 + CF3COOH → CF3H + CF3COO ����������������(1)CF3 + CF3COOD → CF3D + CF3COO ����������������(2) have been studied in the temperature ranges 102-225°C and 153-275°C respectively. The rate constants, based on the value of 1013.36 cm3 mol-1 s-1 for the recombination of CF3 radicals, are given by (k in cm3 mol-1 s-1 and E in J mol-1): logk1 = (10.17�0.12)-(33140�970)/19.145T��������������������� logk2 = (9.51�0.11)-(46090�1010)/19.145T

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 Trifluoromethyl Radicals. IV. Hydrogen Abstraction from Dichlorosilane and Trichlorosilane

1979 ◽  
Vol 32 (5) ◽  
pp. 1017 ◽  
Author(s):  
NL Arthur ◽  
JR Christie ◽  
GD Mitchell
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Temperature Ranges

The hydrogen abstraction reactions of SiH2Cl2 and SiHCl2 with CF3 radicals CF3+SiH2Cl2 → CF3H + SiHCl2 CF3+SiH2Cl3 → CF3H + SiHCl3 have been studied in the temperature ranges 65-227�and 64-294�, respectively. The rate constants, based on the value of 1013.36 cm3 mol-1 s-1 for the recombination of CF3 radicals, are given by (k in cm3 mol-1 s-1, E in J mol-1): logk1 = (12.08 � 0.04)-(25600 � 280)/19.145T logk2 = (11.92 � 0.02)-(27020 � 160)/19.145T

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 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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