A Kinetic Electron Spin Resonance Study of the Transfer of a Hydrogen Atom from α-Tetralin Hydroperoxide to a Tertiary Alkylperoxy Radical

1975 ◽  
Vol 53 (5) ◽  
pp. 623-627 ◽  
Author(s):  
J. H. B. Chenier ◽  
J. A. Howard
Keyword(s):  
Electron Spin Resonance ◽  
Hydrogen Atom ◽  
Electron Spin ◽  
Hydrogen Atom Transfer ◽  
Electron Spin Resonance Study ◽  
Absolute Rate ◽  
Alkyl Hydroperoxides ◽  
Spin Resonance ◽  
Alkylperoxy Radicals ◽  
Spin Resonance Study

A kinetic electron spin resonance spectroscopic study of the reaction of tertiary alkylperoxy radicals with α-tetralin hydroperoxide is reported. The absolute rate constants for this hydrogen atom transfer process (k1) are given by the equation log (k1/M−1 s−1) = (6.0 ± 0.5 ) − (4.5 ± 0.5 )/θ, where θ = 2.303 RT kcal mol−1.A significant isotope effect is obtained when the hydroperoxidic hydrogen is replaced by deuterium, e.g. k1H/k1D at 21° = 9.Other alkyl hydroperoxides, e.g. triphenylmethyl, s-butyl, and 9,10-dihydro-9-anthracyl have approximately the same reactivity to t-ROO• as α-C10H11OOH.

Metal complexes as antioxidants. VI. An electron spin resonance study of the transient cupric complexes formed in the reaction of cupric dialkyldithiocarbamates with alkylperoxy radicals and alkyl hydroperoxides

1978 ◽  
Vol 56 (2) ◽  
pp. 164-169 ◽  
Author(s):  
James Anthony Howard ◽  
John Charles Tait
Keyword(s):  
Electron Spin Resonance ◽  
Hyperfine Interaction ◽  
Metal Complexes ◽  
Electron Spin ◽  
Hyperfine Splitting ◽  
Electron Spin Resonance Study ◽  
Alkyl Hydroperoxides ◽  
Spin Resonance ◽  
Alkylperoxy Radicals ◽  
Spin Resonance Study

The epr spectra of three intermediate copper(II) complexes formed by oxidation of bis[N,N-dialkyl(dithiocarbamato-S,S′)] copper(II) by alkyl hydroperoxides and alkylperoxy radicals are reported. Isotropic and anisotropic spectra of the complexes formed from alkylperoxy radicals enriched with 17O are consistent with the following structures: [Cu(S2CNR2)(OS2CNR2)] (I), [Cu(OS2CNR2)2] (II), and [Cu(OS2CNR2)(O2S2CNR2)] (III). The isotropic 17O hyperfine interaction of I is 19.2 G while the anisotropic spectrum of II indicates that the two oxygen nuclei are equivalent. The anisotropic 17O hyperfine splitting constants are consistent with a structure for these complexes in which the S—O bond(s) is directed out of the plane of the complex and not coordinated to the copper.

The Self-Reaction of sec-Alkylperoxy Radicals: A Kinetic Electron Spin Resonance Study

1972 ◽  
Vol 50 (14) ◽  
pp. 2374-2377 ◽  
Author(s):  
J. A. Howard ◽  
J. E. Bennett
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Rate Constants ◽  
The Self ◽  
Electron Spin Resonance Study ◽  
Absolute Rate ◽  
Arrhenius Plots ◽  
Spin Resonance ◽  
Alkylperoxy Radicals ◽  
Spin Resonance Study

Absolute rate constants for the self-reaction of cyclopentylperoxy, cyclopentenylperoxy, and sec-butylperoxyradicals have been determined over a 125 °C temperature range. Arrhenius plots derived from these rate constants suggest that the mechanism for this reaction is more complex than the currently accepted Russell mechanism.

An Electron Spin Resonance Study of Hydrogen Atom Reactions with Butenes Trapped in Aqueous Sulfuric Acid Glasses

1974 ◽  
Vol 52 (19) ◽  
pp. 3410-3414 ◽  
Author(s):  
Howard Reginald Falle ◽  
Frederick Peter Sargent
Keyword(s):  
Electron Spin Resonance ◽  
Sulfuric Acid ◽  
Hydrogen Atom ◽  
Electron Spin ◽  
Qualitative Agreement ◽  
Electron Spin Resonance Study ◽  
Torsional Motion ◽  
Spin Resonance ◽  
Percentage Ratio ◽  
Spin Resonance Study

Hydrogen atom reactions with butenes trapped in sulfuric acid glasses yield sec-butyl radicals by addition and methallyl radicals by abstraction. The character of the e.s.r. spectra due to the CH3ĊHCH2CH3 radicals depends on whether cis-2-butene or trans-2-butene was the precursor. Computer simulated spectra indicate that the most probable conformation for the CH3ĊHCH2CH3 radicals derived from cis-2-butene and trans-2-butene are 'oblique' and 'trans', respectively. Qualitative agreement between the simulated and experimental spectra is achieved by adding together the spectra computed for CH3ĊHCH2CH3 and [Formula: see text] in the percentage ratio 40:60. In computing the spectra for CH3ĊHCH2CH3, it is assumed that the radicals are distributed over a range of conformations and can undergo torsional motion.

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