Kinetic Isotope Effects in the Radiation-induced Oxidation of Alcohols by Hydrogen Peroxide in Aqueous Solution

1971 ◽  
Vol 49 (15) ◽  
pp. 2619-2619 ◽  
Author(s):  
C. E. Burchill ◽  
G. F. Thompson
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Oxidation Of Alcohols ◽  
Radiation Induced

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Kinetic Isotope Effects in the Radiation-induced Oxidation of Alcohols by Hydrogen Peroxide in Aqueous Solution

1971 ◽  
Vol 49 (8) ◽  
pp. 1305-1309 ◽  
Author(s):  
C. E. Burchill ◽  
G. F. Thompson
Keyword(s):  
Hydrogen Peroxide ◽  
Kinetic Isotope Effect ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Chain Oxidation ◽  
Oxidation Of Methanol ◽  
Kinetic Isotope ◽  
Oxidation Of Alcohols ◽  
Radiation Induced

By using selectively deuterated alcohols it is demonstrated that abstractions from both α and β positions of 2-propanol and ethanol contribute to the overall mechanism for the radiation-induced chain oxidation of these alcohols by hydrogen peroxide. Kinetic isotope effects are measured for abstraction of H by OH from 2-propanol and ethanol at both α and β positions and for the H atom transfer reaction from the alcohol to the β radical. The chain oxidation of methanol shows no primary kinetic isotope effect on substitution of CD3OH.

Radiation-induced Oxidation of 2-Propanol by Nitrous Oxide in Alkaline Aqueous Solution

1972 ◽  
Vol 50 (11) ◽  
pp. 1751-1756 ◽  
Author(s):  
C. E. Burchill ◽  
G. P. Wollner
Keyword(s):  
Aqueous Solution ◽  
Rate Constant ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Chain Mechanism ◽  
Radical Chain ◽  
Kinetic Isotope ◽  
Alkaline Aqueous Solution ◽  
Radiation Induced ◽  
Solution Proceeds

The radiation-induced oxidation of 2-propanol to acetone by N2O in alkaline aqueous solution proceeds via a free radical chain mechanism independent of pH above 12.5. The results are explained by abstraction of H from 2-propanol by O− at both the α and β positions (85% α attack). Chain propagation is by reaction of the α radical anion, (CH3)2ĊO−, with N2O with a rate constant of (3.8 ± 0.4) × 104 M−1 s−1 and by reaction of the β radical, ĊH2(CH3)CHOH, with 2-propanol to give the α radical with a rate constant of 430 ± 30 M−1 s−1.The conclusions are supported by the demonstration of kinetic isotope effects for selectively deuterated alcohols.

Kinetics and mechanism of the oxidation of alcohols by ferrate ion

1993 ◽  
Vol 71 (9) ◽  
pp. 1394-1400 ◽  
Author(s):  
Donald G. Lee ◽  
Huifa Gai
Keyword(s):  
Transition Metal Oxides ◽  
Isotope Effects ◽  
Substituent Effects ◽  
Kinetic Isotope Effects ◽  
Reaction Rates ◽  
Radical Intermediates ◽  
Kinetic Isotope ◽  
Oxidation Of Alcohols ◽  
Aliphatic Ether ◽  
High Valent

A kinetic study of the reduction of ferrate ion under basic conditions has been completed. The observation that a typical aliphatic ether, tetrahydrofuran, is oxidized at a rate comparable to that of aliphatic alcohols, such as cyclopentanol, indicates that the reaction between ferrate and alcohols is likely initiated by attack of the oxidant at an α-C—H bond, a conclusion that is consistent with the occurrence of primary deuterium kinetic isotope effects (2.8–4.3 at 25 °C) when α-hydrogens are replaced by deuterium. Because only acyclic products are obtained from the oxidation of cyclobutanol by ferrate, it may be concluded that free radical intermediates are involved in the reaction. The insensitivity of the reaction rates to substituent effects during the oxidation of substituted mandelic acids indicates that substantial charges are not built up in the transition state. All of these observations are most readily accommodated by a mechanism in which the reaction is initiated by a 2 + 2 addition of an Fe=O bond to the α-C—H of an alcohol to give an organometallic intermediate that subsequently decomposes by homolytic cleavage of the resulting C—Fe bond. Comparisons are made with the reactions between alcohols and other high-valent transition metal oxides.

scholarly journals Horseradish peroxidase. XXIX. Reactions in water and deuterium oxide: cyanide binding, compound I formation, and reactions of compounds I and II with ferrocyanide

1978 ◽  
Vol 56 (22) ◽  
pp. 2844-2852 ◽  
Author(s):  
H. Brian Dunford ◽  
W. Donald Hewson ◽  
Håkan Steiner
Keyword(s):  
Hydrogen Peroxide ◽  
Horseradish Peroxidase ◽  
Kinetic Isotope Effect ◽  
Deuterium Oxide ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Compound I ◽  
Kinetic Isotope ◽  
Cyanide Binding ◽  
Compound Ii

The kinetics of the reactions of hydrogen peroxide and cyanide with native horseradish peroxidase, as well as reactions of compounds I and II with ferrocyanide have been studied in ordinary water and in deuterium oxide at 25 °C and ionic strength 0.11 using a stopped-flow apparatus. Rate constants for all reactions were measured over a wide range of acidity in both solvents from which equilibrium and kinetic isotope effects were evaluated. Protonation of an ionizable group on the enzyme with a pKa value of 4.15 ± 0.05 in water inhibits the reactions with both hydrogen peroxide and cyanide. A significant kinetic isotope effect, kH/kD = 1.6 ± 0.1, was measured for compound I formation whereas no significant kinetic isotope effect was found for cyanide binding. On the basis of these findings, a partial mechanism for compound I formation is proposed in which the group of pKa 4.15 plays a crucial role. The pH dependencies of the ferrocyanide reaction in the pH interval 4.5–10.8 confirmed the role of an acid group with a pKa of 5.2 for compound I and for compound II a pKa of 8.6 and another with a value lower than that encompassed by the pH range of the study. Equilibrium isotope effects were found but no kinetic isotope effects for either the reaction of compound I or of compound II This suggests that there are no rate-limiting proton transfers in the reactions between ferrocyanide and compounds I and II of horseradish peroxidase. The only reducing substrates which exhibit positive kH/kD values possess a labile proton.

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