Electron Spin Resonance Studies of the Radiolysis of Aliphatic Amines at 77 °K

Several frozen aliphatic amines have been γ-irradiated at 77 °K and the electron spin resonance (e.s.r.) spectra of the trapped radicals obtained at 77 °K and on warming. Radiolysis of methyl, ethyl and isopropyl amines produces predominantly alkylamino [Formula: see text] radicals. The proton hyperfine (h.f.) couplings of [Formula: see text] radicals are 10–30% larger than those in the corresponding isoelectronic alkyl radicals and the parallel component of the 14N coupling is about 35 G. Restricted rotation of alkyl groups occurs at 77 °K in some cases. On warming from 77 °K, the [Formula: see text] radicals generally abstract from the solvent or isomerize to produce radicals of the aminoalkyl type (e.g. RĊHNH2). The alkyl proton h.f. splittings of these latter radicals are 20–40% lower than in the corresponding alkyl radicals, and the observed 14N coupling was [Formula: see text] in ĊH2NR2 and [Formula: see text] in (CH3)2ĊNH2 and CH3ĊHNH2. The amino proton couplings in the aminoalkyl radicals were not resolved. Irradiated dimethylamine produces both (CH3)2N and CH2N(CH3) radicals, but (CH3)2N disappears on warming. Only ĊH2N(CH3)2 was observed after irradiation of (CH3)3N at 77 °K. Solid methoxyamine (giving CH3ONH) and tert-butyl-amine were also studied.

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Electron Spin Resonance Studies of the Radiolysis of Aliphatic Amines Adsorbed on Silica Gel

Canadian Journal of Chemistry ◽

10.1139/v71-306 ◽

1971 ◽

Vol 49 (11) ◽

pp. 1880-1887 ◽

Cited By ~ 13

Author(s):

P. Wardman ◽

D. R. Smith

Keyword(s):

Electron Spin Resonance ◽

Silica Gel ◽

Electron Spin ◽

Active Site ◽

Cation Radical ◽

Aliphatic Amines ◽

Polycrystalline Solid ◽

Spin Resonance ◽

Butyl Amine ◽

Surface Active

Several aliphatic amines have been adsorben in sub-monolayer amounts on silica gel and γ-irradiated at 77 °K. The electron spin resonance (e.s.r.) spectra of the radicals trapped on the surface at 77 °K were similar, in most cases, to the spectra obtained after irradiating the corresponding polycrystalline solid amine at 77 °K. Methyl-, ethyl-, n-propyl, and n-butylamines all gave [Formula: see text] radicals, and dimethylamine gave [Formula: see text] radicals. The radical cation [Formula: see text] was observed in the case of trimethylamine. Adsorbed methoxy-amine and t-butyl amine have also been studied and the cation-radical of the latter tentatively identified. The results are discussed in terms of reaction of the adsorbed amine with a surface active site.

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Radiation damage in polyethylene as studied by electron spin resonance

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1961.0113 ◽

1961 ◽

Vol 262 (1309) ◽

pp. 207-218 ◽

Cited By ~ 42

Keyword(s):

Electron Spin Resonance ◽

Electron Spin ◽

Alkyl Radical ◽

Room Temperature ◽

Chemical Properties ◽

Resonance Method ◽

Alkyl Radicals ◽

Spin Resonance ◽

Physical And Chemical ◽

Kinetics Of

The electron spin resonance method was employed to study the nature, concentration and kinetics of the disappearance under varying conditions of radicals produced in polyethylene by fast electron irradiation at 77°K. The predominant radical species at 77°K is the alkyl radical —CH 2 —ĊH—CH 2 —. On being warmed to room temperature it disappears rapidly, revealing a more stable unidentified radical. The kinetics of the decay at room temperature of both radicals was observed. Their stabilities were found to vary in polyethylene samples of differing physical and chemical properties. G values for these radicals are given. Comparison was made with spectra obtained under similar conditions with two pure paraffins and a pure olefin to evaluate the effect of crystallinity branching, molecular weight and unsaturation. In the olefin there is evidence for a build-up of allyl radicals due to the encounter of an alkyl radical with main chain unsaturation. This supports the view that alkyl radicals are mobile, and cross-linking occurs when two such radicals meet.

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