Deuterium isotope effect on hydrogen atom abstraction by methyl radicals in acetonitrile at 77 K. Evidence for tunneling

1977 ◽  
Vol 81 (6) ◽  
pp. 516-520 ◽  
Author(s):  
Estel D. Sprague
Keyword(s):  
Hydrogen Atom ◽  
Isotope Effect ◽  
Hydrogen Atom Abstraction ◽  
Methyl Radicals ◽  
Deuterium Isotope Effect

Stereochemistry of Dehydrogenation by D-Galactose Oxidase

1971 ◽  
Vol 49 (21) ◽  
pp. 3429-3437 ◽  
Author(s):  
A. Maradufu ◽  
G. M. Cree ◽  
A. S. Perlin
Keyword(s):  
Hydrogen Atom ◽  
Isotope Effect ◽  
Galactose Oxidase ◽  
Relative Impact ◽  
Chemical Transformations ◽  
Product Analysis ◽  
Deuterium Isotope Effect ◽  
Oxidation Rates ◽  
Selective Chemical ◽  
Sugar Derivatives

The stereochemistry of dehydrogenation of the primary carbinol group of D-galactose by D-galactose oxidase has been determined. Using D-galactose-6-d and methyl β-D-galactopyranoside-6-d, it has been established that the reaction involves removal of the pro-S 6-hydrogen atom. This conclusion is based on product analysis, and on the relative impact of the deuterium isotope effect on oxidation rates of substrates having different R:S deuteration patterns. The absolute configurations at C-6 of these substrates have been determined by selective chemical transformations to products of known configuration. The rotational conformation of the 6-carbinol group of D-galactose and its possible relationship to the specificity of the enzyme are discussed, as well as the stereochemistry of reductive deuteration of aldehydo sugar derivatives.

Initiation mechanisms in radical polymerizations : Reaction of cumyloxy radicals with methyl methacrylate and styrene

1982 ◽  
Vol 35 (10) ◽  
pp. 2013 ◽  
Author(s):  
E Rizzardo ◽  
AK Serelis ◽  
DH Solomon
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Methyl Methacrylate ◽  
Rate Constants ◽  
Polymer Structure ◽  
Hydrogen Atom Abstraction ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Constant Rate ◽  
Radical Generation

Cumyloxy (1-methyl-1-phenylethoxy) radicals have been generated by thermolysis (60�) of dicumyl hyponitrite in methyl methacrylate and styrene. The carbon-centred radicals formed by interaction of cumyloxyl with the respective monomers were trapped as stable adducts of 1,1,3,3-tetramethyl-isoindolin-2-yloxyl. Extensive hydrogen atom abstraction and methyl radical generation as well as double-bond addition were observed in methyl methacrylate. Styrene underwent only double-bond addition by both cumyloxy and methyl radicals. Some possible implications of these results for polymer structure are discussed. A kinetic study of the decomposition of dicumyl hyponitrite in cyclohexane at various temperatures gave k=7.7 × 1014exp(-13600/T) s-1 for the rate constant. Rate constants for the addition of cumyloxyl to methyl methacrylate (k ≈ 2 × 104 dm3 mol-1 s-1) and styrene (k≈2 × 105 dm3 mol-1 s-1) at 60�have been estimated.

Isotope effect on hydrogen atom abstraction reaction by recoil tritium atoms in xenon-ethane-perdeuteroethane mixtures at 77 K

1983 ◽  
Vol 87 (7) ◽  
pp. 1201-1204 ◽  
Author(s):  
Yasuyuki Aratono ◽  
Enzo Tachikawa ◽  
Tetsuo Miyazaki ◽  
Shigeo Nagaya ◽  
Yoshiteru Fujitani ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Isotope Effect ◽  
Hydrogen Atom Abstraction ◽  
Abstraction Reaction

ISOTOPE EFFECTS IN NEUTRAL H2O–D2O IRRADIATED SOLUTIONS AND THE NATURE OF THE REDUCING RADICAL

1962 ◽  
Vol 40 (10) ◽  
pp. 1903-1908 ◽  
Author(s):  
Chava Lifshitz
Keyword(s):  
Hydrogen Atom ◽  
Water Molecule ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Sodium Formate ◽  
Alternative Possibilities ◽  
X Rays ◽  
Deuterium Isotope Effect ◽  
Deuterium Concentration ◽  
Single Water Molecule

Neutral solutions of sodium formate in H2O–D2O mixtures were irradiated by 200-kv X rays. The atomic deuterium isotope effect (αA) and its dependence on deuterium concentration were determined. In a 1 × 10−1 M HCOONa, 96% D2O solution, G(hydrogen) = 1.14 and αA = 4.3. It is concluded that the hydrogen atom cannot be formed from a single water molecule. Possible mechanisms of hydrogen atom formation are discussed. The alternative possibilities for the atoms to react as H or H2O− are viewed in the light of the proposed mechanisms.

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