Theory of the Hyperfine Splittings of Pi‐Electron Free Radicals. III. Methyl Radical in a Pyramidal Configuration: Temperature Dependence of the Hyperfine Splittings

1970 ◽  
Vol 52 (11) ◽  
pp. 5596-5606 ◽  
Author(s):  
S. Y. Chang ◽  
E. R. Davidson ◽  
G. Vincow
Keyword(s):  
Free Radicals ◽  
Temperature Dependence ◽  
Methyl Radical ◽  
Pyramidal Configuration ◽  
Hyperfine Splittings

Chlorine Hyperfine Splittings in Phenoxy Free Radicals

Nature ◽  
1964 ◽  
Vol 204 (4962) ◽  
pp. 991-992 ◽  
Author(s):  
B. T. ALLEN ◽  
W. VANNESTE
Keyword(s):  
Free Radicals ◽  
Hyperfine Splittings

Reactions of free radicals with aromatic compounds in the gaseous phase. II. Kinetics of the reaction of methyl radicals with phenol

1965 ◽  
Vol 18 (1) ◽  
pp. 20 ◽  
Author(s):  
MFR Mulcahy ◽  
DJ Williams
Keyword(s):  
Free Radicals ◽  
Gaseous Phase ◽  
Hydrogen Abstraction ◽  
High Reactivity ◽  
Phenoxy Radical ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Kinetics Of Formation ◽  
Phenolic Substances ◽  
Kinetics Of

Knowledge of the reactivity of phenols towards simple free radicals is needed to throw light on the behaviour of the phenolic substances involved in the pyrolysis of coal and other organic materials. In the present investigation the reaction between methyl radicals and phenol vapour has been studied a t total pressures from 0.5 to 3 cmHg and temperatures from 445 to 547°K, the concentrations of methyl radicals and phenol being varied from 2 × 10-12 to 4 × 10-11 and 1 × 10-8 to 8 × 10-7 mole cm-3 respectively. The main products identified by gas chromatography were methane and o- and p-cresol, together with a little anisole and 2,4- and 2,6-dimethylphenol. The cresols are produced via hydrogen abstraction Diagram followed by combination of a methyl radical at a ring position of the phenoxy radical either ortho or para to the oxygen atom, e.g. in the case of the para position: Diagram The kinetics can be explained by postulating (a) that the keto forms of the cresols (methylcyclohexadienones) formed initially by reaction (6) have a finite lifetime in the gaseous phase and (b) that these molecules, which contain a tertiary hydrogen atom α to a system of a carbonyl bond and two carbon-carbon double bonds, partly undergo hydrogen abstraction by methyl radicals before they are able to enolize: CH3· + (HCH3 = C6H4 = O → CH4 + CH3C6H4O· The mechanism is consistent with the kinetics of formation of methane, the distribu- tion of the free electron in the phenoxy radical, the formation of o- and p-cresols as major products, the kinetics of formation of the cresols, and the high reactivity of the intermediate product towards methyl radicals.

An Electrolytically Generated, Localized Hole Center in Quartz

1989 ◽  
Vol 44 (4) ◽  
pp. 278-282
Author(s):  
A. B. Vassilikou-Dova ◽  
K. Eftaxias ◽  
G. Lehmann
Keyword(s):  
Activation Energy ◽  
Electron Paramagnetic Resonance ◽  
Temperature Dependence ◽  
Free Electron ◽  
Room Temperature ◽  
Hole Center ◽  
Paramagnetic Resonance ◽  
Tentative Model ◽  
Hyperfine Splittings ◽  
Electron Paramagnetic

Abstract In natural smoky quartz and neutron-irradiated, initially colorless quartz a new hole center was formed electrolytically at temperatures near 1100 K in addition to the well-known smoky quartz center. Unlike the latter its electron paramagnetic resonance spectra can already be measured at room temperature due to firm localization of the hole on one oxygen. It is characterized by fairly small hyperfine splittings due to Al impurity and significant deviations of all three principal g factors from that of a free electron. A tentative model for the structure of this center is proposed.An activation energy of 215 kJ/mol was determined for this electrolytic coloration from the temperature dependence of the electrolysis currents.

Hyperfine Splittings in the Paramagnetic Resonances of Free Radicals

1953 ◽  
Vol 21 (12) ◽  
pp. 2227-2228 ◽  
Author(s):  
S. I. Weissman ◽  
J. Townsend ◽  
Donald E. Paul ◽  
G. E. Pake
Keyword(s):  
Free Radicals ◽  
Hyperfine Splittings
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