Lyoluminescence and spin trapping

1982 ◽  
Vol 60 (12) ◽  
pp. 1549-1559 ◽  
Author(s):  
Kamil V Ettinger ◽  
Alexander R Forrester ◽  
Charles H Hunter
Keyword(s):  
Spin Trap ◽  
Light Yield ◽  
Spin Trapping ◽  
Water Soluble ◽  
Peroxyl Radicals ◽  
Nitroso Compounds ◽  
Γ Irradiation ◽  
Alkyl Radicals ◽  
Emitting Species ◽  
Aromatic Nitroso Compounds

The chemical origin of lyoluminescence has been probed using spin trapping techniques. Radicals derived from amino acids and saccharides by γ-irradiation in the solid state have been identified after trapping with aliphatic and aromatic nitroso compounds. Most of the radicals trapped were secondary alkyl radicals. Reaction of peroxyl radicals derived therefrom are thought to produce the emitting species (excited carbonyl compound and/or singlet oxygen). The effect which thermal annealing of the solids after γ-irradiation has on (a) the concentration of radicals in the solid, (b) the concentration of trapped radicals, and (c) the light yield has been investigated. One new water-soluble spin trap has been prepared.

From early spin-trapping experiments to acyl nitroxide chemistry: synthesis of and spin trapping with a water-soluble nitrosopyrazole derivative

1982 ◽  
Vol 60 (12) ◽  
pp. 1587-1593 ◽  
Author(s):  
M John Perkins ◽  
Harparkash Kaur
Keyword(s):  
Spin Trap ◽  
Preliminary Investigation ◽  
Spin Trapping ◽  
Water Soluble ◽  
Nitroso Compounds ◽  
Nitroxide Radicals ◽  
Personal View ◽  
Spin Traps ◽  
Subsequent Investigation

A personal view of early experiments which led to the use of C-nitroso-compounds as spin traps is presented, and it is shown how these experiments resulted in the first isolation, and subsequent investigation, of acyl nitroxide radicals: the use of 1-methyl-4-nitroso-3,5-diphenylpyrazole as a spin trap, and the preparation and preliminary investigation of its water-soluble analogue (1) are described.

Spin trapping by use of nitrosodurene and its derivatives

1982 ◽  
Vol 60 (12) ◽  
pp. 1532-1541 ◽  
Author(s):  
Ryusei Konaka ◽  
Shigeru Terabe ◽  
Taiichi Mizuta ◽  
Shigeru Sakata
Keyword(s):  
Hydrogen Peroxide ◽  
Esr Spectra ◽  
Spin Trapping ◽  
Nitroso Compounds ◽  
Spin Adduct ◽  
Spin Traps ◽  
Spectral Pattern ◽  
Alkyl Radicals ◽  
Alkyl Hydroperoxides ◽  
Tert Butyl Hydroperoxide

In spin trapping the N-methyl-N-phenylaminomethyl radical with nitrosodurene, an esr spectmm exhibiting line width alternation was observed despite the normal spectral pattern found with the use of nitroso-tert-butane. Nitrosodurene derivatives, N-duryl nitrone and methyl N-duryl nitrone, have been revealed to be other excellent spin traps for the N-, 0-, and S-centered radicals. Spin adducts of these radicals, which can be independently prepared by spin trapping with nitrosodurene, are stable and can be easily discriminated by large differences in β-hydrogen splittings or characteristic patterns. Methyl N-duryl nitrone reacted with tert-butyl hydroperoxide to give a spin adduct which could be clearly distinguished in the esr spectra from the tert-butoxy adducts prepared independently from other sources. Accordingly, it seems to be the tert-butylperoxy adduct. Similarly, hydrogen peroxide gave a different spectrum from the hydroxy adducts. Alkyl hydroperoxides caused molecule-induced homolysis with the nitroso compounds to produce alkoxy adducts of the respective nitroso compounds. Some phenyl and duryl alkoxy nitroxides undergo decomposition to give alkyl radicals which were trapped by the nitroso compounds.

Promoters for the Reaction of Rubber with Carbon Black

1955 ◽  
Vol 28 (3) ◽  
pp. 895-905 ◽  
Author(s):  
Kenneth W. Doak ◽  
George H. Ganzhorn ◽  
Bernard C. Barton
Keyword(s):  
Tensile Strength ◽  
Carbon Black ◽  
Cumene Hydroperoxide ◽  
Butyl Rubber ◽  
Nitroso Compounds ◽  
Active Centers ◽  
Alkyl Radicals ◽  
Styrene Copolymers ◽  
Aromatic Nitroso Compounds ◽  
Butadiene Styrene

Abstract Heating unvulcanized mixtures of rubber and carbon black gives increased electrical resistivity, reduced hysteresis and hardness, higher modulus, and increased abrasion resistance to the vulcanizate. This is believed to result from improved dispersion of carbon black, accompanying a chemical reaction between rubber and carbon black. Butyl rubber, with low unsaturation, reacts more slowly than Hevea rubber or butadiene-styrene copolymers (GR-S). Chemical promoters decrease the time and temperature required for the reaction. Certain quinones and aromatic nitroso compounds are effective in both Hevea and Butyl rubber. t-Butyl perbenzoate and cumene hydroperoxide are particularly effective in Hevea rubber and GR-S containing channel black, and when used in optimum amounts, do not adversely affect tensile strength. Hexachlorocyclopentadiene and hexachlorophenol are effective in both Hevea and Butyl rubber, l,3-Dichloro-5,5-dimethylhydantoin and hexachlorocyclopentadiene are effective in Butyl containing channel or furnace blacks. Chemical promoters are believed to initiate allylic or alkyl radicals on rubber chains, which react with active centers on carbon black, forming primary valence bonds.

Formation and photolysis of alkyl and peroxy radicals in dilute glass matrices

1976 ◽  
Vol 54 (24) ◽  
pp. 3833-3838 ◽  
Author(s):  
Frank Cuthbert Adam ◽  
Iain R. H. Marshall
Keyword(s):  
Molecular Oxygen ◽  
Spin Trap ◽  
Peroxy Radicals ◽  
Γ Irradiation ◽  
Radical Pairs ◽  
Alkyl Radicals ◽  
Butyl Radical ◽  
The Matrix ◽  
Glass Matrices ◽  
Hydrocarbon Media

The use of molecular oxygen as a spin trap in rigid glassy hydrocarbon media at 77 K is investigated. By slight warming of the matrix, oxygen is found to effectively scavenge the isolated alkyl radicals produced by γ-irradiation to give RO2•, but does not react with radical pairs lying in the ionization tracks. The yield of scavengable radicals in 3MP is determined and compared to the findings of other workers. The butyl radical yields for γ-irradiated 1.0 mol l−1 butyl chlorides in 3MP are found to be: t-BuCl, 5.8; i-BuCl, 5.1; 2-BuCl, 4.9; and 1-BuCl, 2.2. Alkyl radicals cannot be recovered from either RO2 or BuO2 by uv photolysis due to solvent abstraction reactions, or because of photon induced reactions of the alkyl radicals. Photolysis of the butyl radicals themselves at 253.7 nm give rise to decomposition and solvent abstraction reactions.

Spin trapping with 9-nitrosotriptycene

1982 ◽  
Vol 60 (12) ◽  
pp. 1594-1596 ◽  
Author(s):  
Harparkash Kaur ◽  
M John Perkins ◽  
André Scheffer ◽  
David C Vendor-Morris
Keyword(s):  
Temperature Dependence ◽  
Organic Solvents ◽  
Rate Constant ◽  
Spin Trap ◽  
Esr Spectra ◽  
Spin Trapping ◽  
Alkyl Radicals ◽  
Restricted Rotation

Nitrosotriptycene is found to be a potentially useful spin trap when used in organic solvents; the esr spectra of its spin adducts are simple, but they may show marked temperature dependence due to restricted rotation. Nitrosotriptycene traps primary alkyl radicals with a rate constant of ca. 2 × 107 L mol−1 s−1 at 40°C in benzene.

scholarly journals Studies on the photolytic breakdown of hydroperoxides and peroxidized fatty acids by using electron spin resonance spectroscopy. Spin trapping of alkoxyl and peroxyl radicals in organic solvents

1986 ◽  
Vol 240 (3) ◽  
pp. 789-795 ◽  
Author(s):  
M J Davies ◽  
T F Slater
Keyword(s):  
Fatty Acids ◽  
Spin Trap ◽  
Hydrogen Abstraction ◽  
Spin Trapping ◽  
Ring Closure ◽  
Peroxyl Radicals ◽  
Resonance Spectroscopy ◽  
Oxygen Oxygen ◽  
Low Levels ◽  
Trap Radical

Spin trapping using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) has been used to detect and distinguish between the carbon-centred, alkoxyl, and peroxyl radicals produced during the photolytic decomposition of hydroperoxides. Photolysis of tert-butyl and cumene hydroperoxides, and peroxidized fatty acids, in toluene, with low levels of u.v. light, is shown to lead to the initial production of alkoxyl radicals by homolysis of the oxygen-oxygen bond. Subsequent reaction of these radicals with excess hydroperoxide leads, by hydrogen abstraction, to the production of peroxyl radicals that can be detected as their corresponding adducts with the spin trap. Subsequent breakdown of these adducts produces alkoxyl radicals and a further species that is believed to be the oxidized spin-trap radical 5,5-dimethyl-1-pyrrolidone-2-oxyl. No evidence was obtained at low hydroperoxide concentrations, with either the cumene or lipid alkoxyl radicals, for the occurrence of beta-scission reactions; the production of low levels of carbon-centred radicals is believed to be due to the alternative reactions of hydrogen abstraction, ring closure, and/or 1,2 hydrogen shifts. Analogous experiments with 3,3,5,5-tetramethyl-1-pyrroline N-oxide (TMPO) led only to the trapping of alkoxyl radicals with no evidence for peroxyl radical adducts, this is presumably due to a decreased rate of radical addition because of increased steric hindrance.

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