ChemInform Abstract: Two Functionalized Free Radicals of the Tris(2,4,6-trichlorophenyl) methyl Radical Series. Synthesis, Stability and EPR Analysis

ChemInform ◽  
2010 ◽  
Vol 26 (4) ◽  
pp. no-no
Author(s):  
J. CARILLA ◽  
L. FAJARI ◽  
L. JULIA ◽  
J. RIERA ◽  
L. VIADEL
Keyword(s):  
Free Radicals ◽  
Methyl Radical

Reactions of free radicals with aromatic compounds in the gaseous phase. II. Kinetics of the reaction of methyl radicals with phenol

1965 ◽  
Vol 18 (1) ◽  
pp. 20 ◽  
Author(s):  
MFR Mulcahy ◽  
DJ Williams
Keyword(s):  
Free Radicals ◽  
Gaseous Phase ◽  
Hydrogen Abstraction ◽  
High Reactivity ◽  
Phenoxy Radical ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Kinetics Of Formation ◽  
Phenolic Substances ◽  
Kinetics Of

Knowledge of the reactivity of phenols towards simple free radicals is needed to throw light on the behaviour of the phenolic substances involved in the pyrolysis of coal and other organic materials. In the present investigation the reaction between methyl radicals and phenol vapour has been studied a t total pressures from 0.5 to 3 cmHg and temperatures from 445 to 547°K, the concentrations of methyl radicals and phenol being varied from 2 × 10-12 to 4 × 10-11 and 1 × 10-8 to 8 × 10-7 mole cm-3 respectively. The main products identified by gas chromatography were methane and o- and p-cresol, together with a little anisole and 2,4- and 2,6-dimethylphenol. The cresols are produced via hydrogen abstraction Diagram followed by combination of a methyl radical at a ring position of the phenoxy radical either ortho or para to the oxygen atom, e.g. in the case of the para position: Diagram The kinetics can be explained by postulating (a) that the keto forms of the cresols (methylcyclohexadienones) formed initially by reaction (6) have a finite lifetime in the gaseous phase and (b) that these molecules, which contain a tertiary hydrogen atom α to a system of a carbonyl bond and two carbon-carbon double bonds, partly undergo hydrogen abstraction by methyl radicals before they are able to enolize: CH3· + (HCH3 = C6H4 = O → CH4 + CH3C6H4O· The mechanism is consistent with the kinetics of formation of methane, the distribu- tion of the free electron in the phenoxy radical, the formation of o- and p-cresols as major products, the kinetics of formation of the cresols, and the high reactivity of the intermediate product towards methyl radicals.

Two functionalized free radicals of the tris(2,4,6-trichlorophenyl)methyl radical series. Synthesis, stability and EPR analysis

1994 ◽  
Vol 35 (35) ◽  
pp. 6529-6532 ◽  
Author(s):  
Josep Carilla ◽  
Lluís Fajarí ◽  
Luis Juliá ◽  
Juan Riera ◽  
Lluís Viadel
Keyword(s):  
Free Radicals ◽  
Methyl Radical

Free radicals in the reaction between t-butyl hydroperoxide and titanous ion: Some observations by electron spin resonance spectrometry

1965 ◽  
Vol 18 (8) ◽  
pp. 1177 ◽  
Author(s):  
MFR Mulcahy ◽  
JR Steven ◽  
JC Ward
Keyword(s):  
Aqueous Solution ◽  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Peroxy Radicals ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Butyl Hydroperoxide ◽  
Spin Resonance ◽  
G Value

The reaction between t-butyl hydroperoxide and titanous ion in aqueous solution produces free methyl radicals detectable by electron spin resonance spectrometry (Dixon and Norman). However, the presence of titanous ion in concentrations greater than 0.01M broadens the spectrum of the methyl radical, causing it effectively to disappear at titanous concentrations greater than 0.1M. At hydroperoxide concentrations above 0.25M t-butyl peroxy radicals (identified by a strong single-line spectrum with g-value 2.0136) are produced by the reaction ���������� R. + (CH3)3COOH → RH + (CH3)3COO. Their concentration reaches a maximum about 1 sec after the concentration of the methyl radicals has fallen to an undetectable value and their half-life (≈ 5 sec) is about ten times that of the methyl radicals.

scholarly journals Antioxidant capacity of extracts and isolated compounds from Stryphnodendron obovatum Benth

2009 ◽  
Vol 45 (3) ◽  
pp. 443-452 ◽  
Author(s):  
Analice Martins Daleffi Zocoler ◽  
Andréia Cristina Conegero Sanches ◽  
Ingrid Albrecht ◽  
João Carlos Palazzo de Mello
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Vitamin C ◽  
Ethyl Acetate ◽  
Antioxidant Capacity ◽  
Crude Extract ◽  
Ethyl Acetate Fraction ◽  
Methyl Radical ◽  
Aqueous Fraction ◽  
Significant Difference

The extract from stem bark of Stryphnodendron obovatum Benth. was chromatographed on a Sephadex® LH-20 column, and yielded nine compounds: gallic acid (GA), p-hydroxybenzoic acid (PHB), gallocatechin (GC), epigallocatechin (EPG), 4'-O-methylgallocatechin (MGC), epigallocatechin-(4β→8)-epigallocatechin (EPEP), epigallocatechin-(4β→8)-gallocatechin (EPGC), robinetinidol-(4α→8)-gallocatechin (ROGC) and robinetinidol-(4β→8)-epigallocatechin (ROEP). Evaluation of the antioxidant capacity in vitro by the methods of DPPH free radical (IC50; μg/mL) and reduction of the phosphomolybdenum complex (RAC) gave the following results, respectively: crude extract 4.52 and 0.8242; ethyl-acetate fraction 4.04 and 0.9537; aqueous fraction 5.58 and 0.9275. The crude extract and ethyl-acetate fraction were shown to possess an antioxidant capacity comparable to that of vitamin C (4.93 and 1.0). The values obtained by the DPPH free-radical method for the isolated compounds were IC50 (μM): GA=8.89; PHB=10.12; GC=16.46; EPG=13.20; MGC=21.00; EPEP=6.89; EPGC=4.91; ROGC=7.78 and ROEP=6.20. Vitamin C and trolox showed 30.11 and 30.10, respectively. Dimers showed greater activity in scavenging free radicals, possibly related to the number of hydroxyls. However, compounds without a hydroxyl at position 5 of the A-ring (5-deoxy-proanthocyanidins) did not change the antioxidant activity of the DPPH free radical, as evaluated here for the first time. Among the monomers, there appeared to be a direct relationship in scavenging of free radicals because of the stereochemistry of the compounds. The presence of a methyl radical on the B-ring significantly reduced the scavenging of free radicals of gallocatechin. All compounds showed greater scavenging of radicals than vitamin C and trolox, and these two compounds showed no significant difference from each other.

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