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 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. 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.

Methylene. III. Gas phase reactions with 1-chloropropane

1969 ◽  
Vol 312 (1509) ◽  
pp. 141-161 ◽  
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
The Other ◽  
Gas Phase Reactions ◽  
Other Hand ◽  
Chlorine Substituent ◽  
High Degree ◽  
Singlet Methylene

The work described in this and the following paper is a continuation of that in parts I and II, devoted to elucidation of the mechanism of the reactions of methylene with chloroalkanes, with particular reference to the reactivities of singlet and triplet methylene in abstraction and insertion processes. The products of the reaction between methylene, prepared by the photolysis of ketene, and 1-chloropropane have been identified and estimated and their dependence on reactant pressures, photolysing wavelength and presence of foreign gases (oxygen and carbon mon­oxide) has been investigated. Both insertion and abstraction mechanisms contribute significantly to the over-all reaction, insertion being relatively much more important than with chloroethane. This type of process appears to be confined to singlet methylene. If, as seems likely, there is no insertion into C—Cl bonds under our conditions (see part IV), insertion into C2—H and C3—H bonds occurs in statistical ratio, approximately. On the other hand, the chlorine substituent reduces the probability of insertion into C—H bonds in its vicinity. As in the chloroethane system, both species of methylene show a high degree of selectivity in their abstraction reactions. We find that k S Cl / k S H >7.7, k T Cl / k T H < 0.14, where the k ’s are rate constants for abstraction, and the super- and subscripts indicate the species of methylene and the type of atom abstracted, respectively. Triplet methylene is discriminating in hydrogen abstraction from 1-C 3 H 7 Cl, the overall rates for atoms attached to C1, C2, C3 being in the ratios 2.63:1:0.

MECHANISM AND KINETICS OF THE CH3CH2C(O)OCH2CH3 + OH REACTION: A THEORETICAL STUDY

2011 ◽  
Vol 10 (05) ◽  
pp. 691-709 ◽  
Author(s):  
CONG HOU ◽  
CHENG-GANG CI ◽  
TONG-YIN JIN ◽  
YONG-XIA WANG ◽  
JING-YAO LIUM
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Negative Temperature ◽  
State Theory ◽  
Measured Temperature ◽  
Temperature Range ◽  
Global Rate ◽  
Abstraction Reaction ◽  
Lower Temperature ◽  
Kinetic Calculations

The hydrogen abstraction reaction of CH 3 CH 2 C(O)OCH 2 CH 3 + OH has been studied theoretically by dual-level direct dynamics method. Six H-abstraction channels were found for this reaction. The required potential energy surface information for the kinetic calculations was obtained at the MCG3-MPWB//M06-2X/aug-cc-pVDZ level. The rate constants were calculated by the improved canonical variational transition-state theory with small-curvature tunneling correction (ICVT/SCT) approach in the temperature range of 200–2000 K. It is shown that the "methylene H-abstraction" from the alkoxy end of the ester CH 3 CH 2 C(O)OCH 2 CH 3 is the dominant channel at lower temperature (< 400 K), while the other channels from the acetyl end should be taken into account as the temperature increases and become the competitive ones at higher temperature. The calculated global rate constants are in good agreement with the experimental ones in the measured temperature range and exhibit a negative temperature dependence below 500 K. A four-parameter rate constant expression was fitted from the calculated kinetic data between 200–2000 K.

Reactions of trifluoromethyl radicals. V. Hydrogen abstraction from methyl acetate and methyl (2H3)Acetate

1980 ◽  
Vol 33 (7) ◽  
pp. 1437
Author(s):  
NL Arthur ◽  
PJ Newitt
Keyword(s):  
Isotope Effect ◽  
Rate Constants ◽  
Methoxy Group ◽  
Methyl Acetate ◽  
Kinetic Isotope Effect ◽  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Temperature Range ◽  
Kinetic Isotope ◽  
Acetyl Group

Hydrogen abstraction by CF3 radicals from CH3COOCH3 and CD3COOCH3 has been studied in the temperature range 78-242°, and data have been obtained for the reactions: CF3 + CH3COOCH3 → CF3H+[C3H5O2] �������������(3) CF3 + CH3COOCH3 → CF3H+CH2COOCH3������������ (4) CF3 + CD3COOCH3 → CF3D+CD2COOCH3������������ (6) CF3 + CD3COOCH3 → CF3H+CD3COOCH2������������ (7) The corresponding 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): logk3 = (11.52�0.05)-(35430�380)/19.145T ���� (3)logk4 = (11.19�0.07)-(34680�550)/19.145T ���� (4)logk6 = (11.34�0.06)-(46490�490)/19.145T ���� (6)logk7 = (11.26�0.05)-(36440�400)/19.145T ���� (7)At 400 K, 59% of abstraction occurs from the acetyl group, and 41 % from the methoxy group. The kinetic isotope effect at 400 K for attack on the acetyl group is 25, due mainly to a difference in activation energies.

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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