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.

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.

An Electron Spin Resonance Study of Some Reactions of Pentafluorosulfuranyl (SF5)

1975 ◽  
Vol 53 (16) ◽  
pp. 2361-2364 ◽  
Author(s):  
John Charles Tait ◽  
James Anthony Howard
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Rate Constants ◽  
Arrhenius Equation ◽  
Kinetic Studies ◽  
Electron Spin Resonance Study ◽  
Order Process ◽  
First Order ◽  
Spin Resonance ◽  
Spin Resonance Study

A kinetic electron spin resonance study of the self-reaction of SF5 and a spectroscopic and kinetic e.s.r. study of the reaction of SF5 with 1,1-di-t-butylethylene are reported. This radical undergoes self-reaction by a second-order process and the rate constants are given by the Arrhenius equation log 2k1(M−1 s−1) = (10.3 ± 0.5) − (1.7 ± 0.5)/θ where θ = 2.303RT kcal mol−1. It adds to 1,1-di-t-butylethylene to give (t-Bu)2CCH2SF5 which decomposes by a first-order process with rate constants that obey the expression log k2(s−1) = (13 ± 0.4) − (10 ± 0.2)/θ. Both these rate constants are pertinent to kinetic studies of the photoinduced addition of SF5C1 to olefins.

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.

Electron Spin Resonance Study of the Self-disproportionation of some Semiquinone Radicals in Solution

1972 ◽  
Vol 50 (18) ◽  
pp. 3052-3057 ◽  
Author(s):  
S. K. Wong ◽  
W. Sytnyk ◽  
J. K. S. Wan
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
The Self ◽  
Electron Spin Resonance Study ◽  
Radical Anions ◽  
Electron Polarization ◽  
Semiquinone Radicals ◽  
Spin Resonance ◽  
Rate Of Decay ◽  
Spin Resonance Study

The photolysis of 1,4-benzoquinone, duroquinone, and 1,4-naphthoquinone in isopropanol and in dioxane leads to the observation of e.s.r. spectra of the corresponding semiquinone radicals. The rates of the self-disproportionation of these radicals were measured by the rotating-sector technique. In the case of 1,4-naphthoquinone, unexpected e.s.r. emission was initially observed by photochemically induced dynamic electron polarization of the semiquinone radicals. Photolysis of anthraquinone in isopropanol gives e.s.r. spectra of the anthrasemiquinone radical anions. Their rate of decay was measured and a mechanism for the decay was suggested. The neutral anthrasemiquinone radical, however, was observed when photolyzed in dioxane.

Absolute rate constants for hydrocarbon autoxidation. 28. A low temperature kinetic electron spin resonance study of the self-reactions of isopropylperoxy and related secondary alkylperoxy radicals in solution

1980 ◽  
Vol 58 (7) ◽  
pp. 677-680 ◽  
Author(s):  
Edward Furimsky ◽  
James A. Howard ◽  
Jennifer Selwyn
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Low Temperatures ◽  
Electron Spin Resonance Study ◽  
Absolute Rate ◽  
Unimolecular Decomposition ◽  
Spin Resonance ◽  
Alkylperoxy Radicals ◽  
Tertiary Alkyl ◽  
Spin Resonance Study

Isopropylperoxy radicals at low temperatures exist in equilibrium with di-isopropyl tetroxide. The thermodynamic parameters for this equilibrium are very similar to the values of ΔH0 and ΔS0 for the tert-butylperoxy radical – di-tert-butyl tetroxide equilibrium. Differences in second-order rate constants for mutual destruction of secondary and tertiary alkylperoxy radical appear to result from differences in rate constants for unimolecular decomposition of secondary and tertiary alkyl tetroxides.Isopropylperoxy radicals have the same termination rate constant in the gas phase and in solution.

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