Electron Spin Resonance Studies in Aqueous Solution: Fragmentation of Radical Intermediates Derived from β-Amino Alcohols

1973 ◽  
Vol 51 (24) ◽  
pp. 4009-4017 ◽  
Author(s):  
Terry Foster ◽  
Paul Ronald West
Keyword(s):  
Aqueous Solution ◽  
Electron Spin Resonance ◽  
Amino Alcohols ◽  
Acidic Aqueous Solution ◽  
Radical Intermediates ◽  
Spin Resonance ◽  
Intramolecular Hydrogen ◽  
Neutral Conditions ◽  
Carbonyl Radical ◽  
Acetonyl Radical

In acidic aqueous solution, oxidation of the β-amino alcohols [Formula: see text], I, and [Formula: see text], II, (R = H, alkyl) using the Ti(III)–H2O2 flow technique gave the radicals [Formula: see text], and [Formula: see text]. The spectrum of [Formula: see text] shows restricted rotation about the C1—C2 bond assigned to intramolecular hydrogen bonding.Under neutral conditions, oxidation of I gave the spectrum of •CH2CHO, and of II the acetonyl radical •CH2COCH3. It is proposed that elimination occurs by deprotonation of the abstraction radical in a hydrogen-bonded conformation, followed by rapid fragmentation to yield the α-carbonyl radical.

Restricted Rotation in α-Carbonyl Radicals

1974 ◽  
Vol 52 (3) ◽  
pp. 524-526 ◽  
Author(s):  
Terry Foster ◽  
Dieter Klapstein ◽  
Paul Ronald West
Keyword(s):  
Aqueous Solution ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Reductive Elimination ◽  
Restricted Rotation ◽  
Radical Intermediates ◽  
Spin Resonance ◽  
Radical Fragmentation ◽  
Direct Abstraction

Electron spin resonance spectra of tertiary α-carbonyl radicals, R1R2ĊCOR3 (R1R2R3 = H, alkyl), at 24 °C in aqueous solution show fully restricted rotation about the Ċ—CO bond. The effect is identified by differing h.f.s. constants for equivalent substituents R1 and R2. The radical intermediates are generated by direct abstraction, radical fragmentation, and reductive elimination processes.

scholarly journals Antioxidant activity of Induna apple pomace extract

2005 ◽  
pp. 239-246 ◽  
Author(s):  
Sladjana Savatovic ◽  
Sonja Djilas ◽  
Vesna Tumbas ◽  
Jasna Canadanovic-Brunet ◽  
Gordana Cetkovic
Keyword(s):  
Aqueous Solution ◽  
Antioxidant Activity ◽  
Acetic Acid ◽  
Electron Spin Resonance ◽  
Hydroxyl Radicals ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Methanol Extract ◽  
Apple Pomace ◽  
Spin Resonance

Different concentrations ofmethanol aqueous solution with or without 0.5% acetic acid and 80% acetone were used to achieve the highest yield of extraction of phenolics from Induna apple pomace. The highest content of phenolics (6.38 mg/g) was detected in the 80% methanol extract. The influence of 80% methanol extract of Induna apple pomace on stable l,l-diphenyl-2-picrylhydrazyl (DPPH) and reactive hydroxyl radicals has been investigated by electron spin resonance (ESR) spectroscopy. Based on the obtained results it can be concluded that the investigated extract is more effective in the DPPH test than on the DMPO-OH scavenging. In both cases antioxidant activity increased with increasing concentration of the investigated extract. The high contents ofphenolics (6.38 mg/g), flavonoids (1.01 mg/g) and flavan-3-ols (0.70 mg/g) in 80% methanol extract indicated that these compounds contributed to the antioxidant activity of Induna apple pomace.

Sign in / Sign up

Export Citation Format

Share Document