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.

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.

Hydrogen abstraction from (2H3)methyl acetate by methyl and trifluoromethyl radicals

1981 ◽  
Vol 34 (4) ◽  
pp. 727 ◽  
Author(s):  
NL Arthur ◽  
PJ Newitt
Keyword(s):  
Rate Constants ◽  
Methoxy Group ◽  
Methyl Acetate ◽  
Isotope Effects ◽  
Hydrogen Abstraction ◽  
Kinetic Isotope Effects ◽  
Temperature Range ◽  
Kinetic Isotope ◽  
Acetyl Group

A study of hydrogen abstraction from CH3COOCD3 by CH3 radicals in the temperature range 113-232�, and by CF3 radicals in the range 83-212�, has yielded data on the reactions: CH3+CH3COOCD3 → CH4+CH2COOCD3 (1)CH3+CH3COOCD3 → CH3D+CH3COOCD2 (2) CF3+CH3COOCD3 → CF3H+CH2COOCD2 (3) CF3+CH3COOCD3 → CF3D+CH3COOCD2 (4) The corresponding rate constants, based on the values 1013.34 and 1013.36 cm3 mol-1 s-1 for the recombination of CH3 and CF3 radicals, respectively, are given by (k in cm3 mol-1 s-1 and E in J mol-1): logk1 = (11.31�0.12)-(43500�1030)/19.145T (1) logk1 = (11.31�0.12)-(53460�640)/19.145t (2) logk3 = (11.12�0.06)=(34260�450)/19.145T � (3) logk4 =(10.93�0.12)-(38650�900)/19.145T (4)These results lead to kinetic isotope effects at 400 K for attack on the acetyl group of 11, for the CH3 reaction, and 24, for the CF3 reaction, thus confirming the values we obtained previously. For attack on the methoxy group, the kinetic isotope effects are 8 and 4, for the CH3 and CF3 reactions, respectively.

Efficient oxidation of ethers with pyridine N-oxide catalyzed by ruthenium porphyrins

2015 ◽  
Vol 19 (01-03) ◽  
pp. 411-416 ◽  
Author(s):  
Nobuki Kato ◽  
Yu Hamaguchi ◽  
Naoki Umezawa ◽  
Tsunehiko Higuchi
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Hydrogen Abstraction ◽  
Oxide System ◽  
Cyclic Ethers ◽  
Rate Determining Step ◽  
Kinetic Isotope ◽  
Oxidized Products

We found that oxidation of cyclic ethers with the Ru porphyrin-heteroaromatic N-oxide system gave lactones or/and ring-opened oxidized products with regioselectivity. A relatively high kinetic isotope effect was observed in the ether oxidation, suggesting that the rate-determining step is the first hydrogen abstraction.

Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d1

1984 ◽  
Vol 62 (5) ◽  
pp. 899-906 ◽  
Author(s):  
Jan Niedzielski ◽  
T. Yano ◽  
E. Tschuikow-Roux
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Isotope Effect ◽  
Ground State ◽  
Rate Constants ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope ◽  
Primary Reference ◽  
Hydrogen Deuterium ◽  
Increasing Temperature

The abstraction of hydrogen/deuterium from CH3CHDCl by ground state chlorine atoms produced photolytically from Cl2 has been investigated at temperatures betwen 280 and 368 K. The relative rates for the internal competition[Formula: see text]are found to conform to an Arrhenius rate law:[Formula: see text]These data, taken together with the external competition results for the C2H5Cl/CH3CHDCl system, in conjunction with the competitive results using CH4 as a primary reference, have yielded the rate constants (cm3 s−1):[Formula: see text]The relatively weak primary kinetic isotope effect, kH/kD, decreases with increasing temperature from 1,855 at 280 K to 1.66 at 365 K. The results are compared with those obtained based on the BEBO method. While both the trend and the magnitude of the kinetic isotope effect are satisfactorily predicted, the activation energy is not.

Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 1085-1096 ◽  
Author(s):  
A M Kuznetsov ◽  
Jens Ulstrup
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Rate Constants ◽  
Bovine Serum ◽  
Kinetic Isotope Effect ◽  
Hydrogen Transfer ◽  
Low Frequency ◽  
Specific Rate ◽  
Adiabatic Limits ◽  
Kinetic Isotope

We discuss a broad theoretical frame for hydrogen transfer in chemical and biological systems. Hydrogen tunnelling, coupling between the tunnel modes and the environment, and fluctuational barrier preparation for hydrogen tunnelling are in focus and given precise analytical forms. Specific rate constants are provided for three limits, i.e., the fully diabatic, the partially adiabatic, and the fully adiabatic limits. These limits are all likely to represent real chemical or biological hydrogen transfer systems. The rate constants are referred particularly to the driving force and temperature dependence of the kinetic isotope effect (KIE). The origin of these correlations is different in the three limits. It is rooted in the tunnel factor and weak excitation of the heavier isotopes in the former two limits, giving a maximum for thermoneutral processes. A new observation is that the adiabatic limit also accords with a KIE maximum for thermoneutral processes but the KIE is here reflected solely in the activation Gibbs free energy differences, in this case rooted in the low-frequency environmental nuclear dynamics. Three systems of biological hydrogen tunnelling, viz. lipoxygenase, yeast alcohol dehydrogenase, and bovine serum amine oxygenase, offer unusual new cases for analysis and have been analysed using the theoretical frames. All the systems show large KIEs and strong indications of hydrogen tunnelling. They also represent different degrees of fluctuational barrier preparation, with lipoxygenase as the most rigid and bovine serum amine oxygenase as the softest system.Key words: generalized Born-Oppenheimer scheme, kinetic isotope effect, gated proton transfer, partially adiabatic proton transfer, proton tunnelling in enzyme catalysis.

scholarly journals The H + D2→ HD + D Reaction. Quasiclassical Trajectory Study of Cross Sections, Rate Constants, and Kinetic Isotope Effect

1997 ◽  
Vol 101 (35) ◽  
pp. 6165-6176 ◽  
Author(s):  
F. J. Aoiz ◽  
L. Bañares ◽  
V. J. Herrero ◽  
V. Sáez Rábanos ◽  
I. Tanarro
Keyword(s):  
Isotope Effect ◽  
Cross Sections ◽  
Rate Constants ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope

Kinetic Isotope Effect for Hydrogen Abstraction by•OH Radicals from Normal and Carbon-Deuterated Ethyl Alcohol and Methylamine in Aqueous Solutions†

2003 ◽  
Vol 107 (30) ◽  
pp. 7268-7276 ◽  
Author(s):  
Marija Bonifačić ◽  
David A. Armstrong ◽  
Igor Štefanić ◽  
Klaus-Dieter Asmus
Keyword(s):  
Aqueous Solutions ◽  
Isotope Effect ◽  
Ethyl Alcohol ◽  
Kinetic Isotope Effect ◽  
Hydrogen Abstraction ◽  
Oh Radicals ◽  
Kinetic Isotope
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