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

1971 ◽  
Vol 49 (11) ◽  
pp. 1880-1887 ◽  
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.

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

1971 ◽  
Vol 49 (11) ◽  
pp. 1869-1879 ◽  
Author(s):  
P. Wardman ◽  
D. R. Smith
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Aliphatic Amines ◽  
Methyl Ethyl ◽  
Alkyl Radicals ◽  
Restricted Rotation ◽  
Parallel Component ◽  
Alkyl Groups ◽  
Spin Resonance ◽  
Butyl Amine

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.

ORGANIC AND BIOLOGICAL SPECTROCHEMICAL STUDIES: XXIII. CONFORMATION OF THE p-DIMETHOXYBENZENE CATION RADICAL IN CONCENTRATED SULFURIC ACID

1966 ◽  
Vol 44 (13) ◽  
pp. 1501-1512 ◽  
Author(s):  
W. F. Forbes ◽  
P. D. Sullivan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Electron Spin Resonance ◽  
Sulfuric Acid ◽  
Magnetic Resonance ◽  
Electron Spin ◽  
Cation Radical ◽  
Molecular Orbital Calculations ◽  
Spin Resonance ◽  
Concentrated Sulfuric Acid ◽  
Nuclear Magnetic

The electron spin resonance spectrum of the p-dimethoxybenzene cation radical in concentrated sulfuric acid is interpreted in terms of cis–trans isomerism. Empirical molecular orbital calculations support these assignments. The two isomers are found to possess slightly different "g" values, Δg (cis – trans) being ca. 1.8 × 10−5.Nuclear magnetic resonance and ultraviolet data show that the radical exists in equilibrium with the neutral non-radical species at room temperature, but that sulfonation occurs at higher temperatures. Nuclear magnetic resonance and electron spin resonance data of solutions of p-dimethoxybenzene in D2SO4 show that rapid exchange of the ring protons occurs.

FREE RADICALS OF BIOLOGICAL INTEREST: I. ELECTRON SPIN RESONANCE SPECTRA OF TOBACCO SMOKE CONDENSATES

1967 ◽  
Vol 45 (7) ◽  
pp. 1087-1098 ◽  
Author(s):  
W. F. Forbes ◽  
J. C. Robinson ◽  
G. F. Wright
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Sulfuric Acid ◽  
Electron Spin ◽  
Tobacco Smoke ◽  
Cation Radical ◽  
Fold Increase ◽  
Active Centers ◽  
Radical Species ◽  
Spin Resonance

Smoke condensates, prepared from tobacco smoke, are shown to contain a variety of paramagnetically active centers. Some of these have lifetimes of a few seconds. Smoke condensates, when dissolved in sulfuric acid, give rise to at least two cation radical species. The more short-lived species may be the anthracene or an anthracene-type cation radical species and the more long-lived one may be a cation radical related to, but not identical with, the 3,4-benzpyrene cation radical.When 3,4-benzpyrene is heated to near its melting point, considerably more intense electron spin resonance (e.s.r.) spectra are obtained. The heated benzpyrene sample, when dissolved in sulfuric acid, also gives a more intense, but otherwise similar, spectrum than an unheated sample. These observations indicate that, on heating benzpyrene, additional free radicals are formed, and this may account for the relatively high carcinogenicity of tobacco smoke condensates.The e.s.r. spectrum of 3,4-benzpyrene in sulfuric acid undergoes an approximately 10-fold increase in signal intensity when similar amounts of 3,4-benzpyrene-6,7-quinone are added to the mixture. The latter compound on its own does not afford a detectable signal under these conditions. This indicates that the ability of known carcinogenic substances, such as 3,4-benzpyrene, to give rise to free-radical species can be appreciably affected by the molecular environment.

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