Free-radical reaction

About: Free-radical reaction is a research topic. Over the lifetime, 1919 publications have been published within this topic receiving 56787 citations.

Atmospheric chemistry of N-methyl perfluorobutane sulfonamidoethanol, C4F9SO2N(CH3)CH2CH2OH: kinetics and mechanism of reaction with OH.

Abstract: Relative rate methods were used to measure the gas-phase reaction of N-methyl perfluorobutane sulfonamidoethanol (NMeFBSE) with OH radicals, giving k(OH + NMeFBSE) = (5.8 ± 0.8) × 10-12 cm3 molecule-1 s-1 in 750 Torr of air diluent at 296 K. The atmospheric lifetime of NMeFBSE is determined by reaction with OH radicals and is approximately 2 days. Degradation products were identified by in situ FTIR spectroscopy and offline GC−MS and LC−MS/MS analysis. The primary carbonyl product C4F9SO2N(CH3)CH2CHO, N-methyl perfluorobutane sulfonamide (C4F9SO2NH(CH3)), perfluorobutanoic acid (C3F7C(O)OH), perfluoropropanoic acid (C2F5C(O)OH), trifluoroacetic acid (CF3C(O)OH), carbonyl fluoride (COF2), and perfluorobutane sulfonic acid (C4F9SO3H) were identified as products. A mechanism involving the addition of OH to the sulfone double bond was proposed to explain the production of perfluorobutane sulfonic acid and perfluorinated carboxylic acids in yields of 1 and 10%, respectively. The gas-phase N-dealkylation produc...

Kinetics and Mechanisms of Photocatalytic Degradation of (CH3)nNH4-n+ (0 ≤ n ≤ 4) in TiO2 Suspension: The Role of OH Radicals

Abstract: The photocatalytic degradation of a series of (CH3)nNH4-n+ (0 ≤ n ≤ 4) was systematically studied in the UV-illuminated TiO2 aqueous suspensions at pH ranges of 3−11. By investigating the pH-dependent kinetics and analyzing intermediates and products, we elucidated the mechanistic pathways and the role of OH radicals in the photocatalytic oxidation. The deprotonated neutral species more rapidly degraded than their protonated counterparts for these homologous compounds because the OH radicals favorably reacted with the lone-pair electron on the nitrogen atom. Therefore, the photocatalytic degradation was highly enhanced at alkaline solutions for all substances except (CH3)4N+. The H-atom abstraction (from (CH3)4N+) by OH radicals initiated successive demethylation processes to generate tri-, di-, and monomethylammonium/amine as an intermediate and NH3/NH4+ as a final product. On the other hand, the OH-addition to the N-atom with the lone-pair electron led to NO2-/NO3- whose production was highly favored at...

Free-radical carbon-carbon bond formation in organic synthesis.

Abstract: Organic chemists have begun to use intra- and intermolecular free-radical addition reactions to develop useful synthetic transformations. Carboncentered radicals can form bonds with electron-rich or electron-deficient alkenes, allenes, and acetylenes. Radical addition reactions can also be used to construct hindered carbon-carbon bonds. These characteristics, as well as the large number of functional groups that tolerate free-radical conditions contribute to the importance of such reactions in organic synthesis.

Chemical studies on antioxidant mechanism of curcuminoid: analysis of radical reaction products from curcumin.

Abstract: In the course of studies on the antioxidant mechanism of curcumin, its radical reaction was investigated. Curcumin was reacted with radical species, which were generated from the pyrolysis of 2,2‘-azobis(isobutyronitrile) under an oxygen atmosphere, and the reaction products from curcumin were followed by HPLC. The reaction at 70 °C gave several products, three of which were structurally identified to be vanillin, ferulic acid, and a dimer of curcumin after their isolation. The dimer was a newly identified compound bearing a dihydrofuran moiety, and its chemical structure was elucidated using spectroscopic analyses, especially 2D NMR techniques. A mechanism for the dimer production is proposed and its relation to curcumin's antioxidant activity discussed. The time course and gel permeation chromatography studies of the reaction were also investigated, and the results indicate that the dimer is a radical-terminated product in the initial stage. Keywords: Curcumin; antioxidant; radical termination; dimer; a...