Electron Spin Resonance Studies of Aliphatic Ammonium Ion Radicals in Aqueous Sulfuric Acid Glasses

1974 ◽  
Vol 52 (19) ◽  
pp. 3401-3409 ◽  
Author(s):  
Howard Reginald Falle ◽  
Frederick Peter Sargent
Keyword(s):  
Electron Spin Resonance ◽  
Sulfuric Acid ◽  
Electron Spin ◽  
Qualitative Agreement ◽  
Hydrogen Abstraction ◽  
Ammonium Ion ◽  
Torsional Motion ◽  
Hydrogen Atoms ◽  
Methylene Carbon ◽  
Spin Resonance

The reaction of hydrogen atoms with n-butylammonium ions in 6 M sulfuric acid glasses yields a characteristic eight-line e.s.r. spectrum, which is attributable to CH3ĊHCH2CH2NH3+. Evidence is drawn from computer simulated spectra and from the spectra of other alkylammonium radicals to account for this spectrum. Qualitative agreement between the simulated and experimental spectra is achieved by assuming that the CH3ĊHCH2— moiety can adopt a range of conformations and can also undergo torsional motion about the sp2 carbon – methylene carbon bond. The site of hydrogen abstraction from alkylammonium ions is evidently influenced by both NH3+ and CH3 groups; abstraction tends to occur away from the former and adjacent to the latter.

An Electron Spin Resonance Study of Hydrogen Atom Reactions with Butenes Trapped in Aqueous Sulfuric Acid Glasses

1974 ◽  
Vol 52 (19) ◽  
pp. 3410-3414 ◽  
Author(s):  
Howard Reginald Falle ◽  
Frederick Peter Sargent
Keyword(s):  
Electron Spin Resonance ◽  
Sulfuric Acid ◽  
Hydrogen Atom ◽  
Electron Spin ◽  
Qualitative Agreement ◽  
Electron Spin Resonance Study ◽  
Torsional Motion ◽  
Spin Resonance ◽  
Percentage Ratio ◽  
Spin Resonance Study

Hydrogen atom reactions with butenes trapped in sulfuric acid glasses yield sec-butyl radicals by addition and methallyl radicals by abstraction. The character of the e.s.r. spectra due to the CH3ĊHCH2CH3 radicals depends on whether cis-2-butene or trans-2-butene was the precursor. Computer simulated spectra indicate that the most probable conformation for the CH3ĊHCH2CH3 radicals derived from cis-2-butene and trans-2-butene are 'oblique' and 'trans', respectively. Qualitative agreement between the simulated and experimental spectra is achieved by adding together the spectra computed for CH3ĊHCH2CH3 and [Formula: see text] in the percentage ratio 40:60. In computing the spectra for CH3ĊHCH2CH3, it is assumed that the radicals are distributed over a range of conformations and can undergo torsional motion.

Hydrogen abstraction by thermal hydrogen atoms at 10–30 K: Electron spin resonance evidence

1978 ◽  
Vol 56 (3) ◽  
pp. 494-496 ◽  
Author(s):  
Machio Iwasaki ◽  
Kazumi Toriyama ◽  
Hachizo Muto ◽  
Keichi Nunome
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Hydrogen Abstraction ◽  
Hydrogen Atoms ◽  
Spin Resonance

FREE RADICALS OF BIOLOGICAL INTEREST: PART II. ELECTRON SPIN RESONANCE (ESR) SPECTRA OF 2537 A IRRADIATED AMINO ACIDS

1967 ◽  
Vol 45 (12) ◽  
pp. 1831-1839 ◽  
Author(s):  
W. F. Forbes ◽  
P. D. Sullivan
Keyword(s):  
Amino Acids ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Hydrogen Abstraction ◽  
Esr Spectra ◽  
Side Chain ◽  
Biological Interest ◽  
Spin Resonance ◽  
Cyclohexadienyl Radical ◽  
Secondary Radical

Polycrystalline amino acids, when irradiated with 2537 Å light, afford a variety of electron spin resonance signals. These signals are generally stable at room temperature for relatively long periods of time. For a number of the spectra obtained, there is evidence that more than one radical species contributes to the observed spectra. The signals obtained frequently differ from those obtained on exposure to ionizing radiation. The postulated species formed can often be visualized as being formed by effective hydrogen abstraction from the alkyl-substituted tertiary carbon atom or from the —OH, —SH or —NH group contained in the side chain. For L-phenylalanine a secondary radical is obtained, which is ascribed to a cyclohexadienyl radical.

Electron spin resonance observations of photochemically generated contact ammonium ion-pairs of fluoro-substituted ketones

1979 ◽  
Vol 57 (5) ◽  
pp. 600-602 ◽  
Author(s):  
K. S. Chen ◽  
T. Foster ◽  
J. K. S. Wan
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Ion Pairs ◽  
Esr Spectra ◽  
Ammonium Ion ◽  
Spin Resonance ◽  
Photochemical Systems

Contact radical ion-pairs of ammonium and fluoro-substituted ketones were generated in photochemical systems and their here-to-fore elusive esr spectra were characterized.

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.

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