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Reduction by Free Radicals

Reduction by Free Radicals.—Cohalt. Reduction of two cobalt(m) complexes (4) and (5) by Me2COH radicals has been studied to assess the role of the carb-oxylate group in intramolecular electron-transfer processes. In each case [Pg.117]

The complex [Co(bipy)3] + reacts rapidly (A= 10 — 10 s ) with reducing [Pg.117]

These results conflict with previous work, and it is speculated that the effects observed there were caused by a small fraction of eaq reacting with [Co(bipy)n] + (/ = 1, 2, or 3) or free bipy. [Pg.117]

Limited data for [Co(phen)3] + are explicable on the same basis as those for [Co(bipy)3] +, except that detachment of a phen ligand [reaction (28)] was not observed. [Pg.118]

[Fe(phen)3] + shows similar behaviour to its cobalt analogue it is rapidly reduced by H to stable [Fe(phen)3] + (A =5 x 10 There is no evi- [Pg.118]


Fig. 1. Schematic description of colloidal metal-catalysed reductions by free radicals... Fig. 1. Schematic description of colloidal metal-catalysed reductions by free radicals...
Asahi M, Asahi K, Wang X, Lo EH. Reduction of tissue plasminogen activator-induced hemorrhage and brain injury by free radical spin trapping after embolic focal cerebral ischemia in rats. J Cereb Blood Flow Metab 2000 20 452 57. [Pg.118]

Bolli, R., Jeroudi, M.O., Patel, B.S., Aruoma, O.I., Halliwell, B., Lai, E.K. and McCay, P.B. (1989). Marked reduction of free radical generation and contractile dysfunction by antioxidant therapy begun at the time of reperfiision. Circ. Res. 65, 607-622. [Pg.69]

Additionally, it has been noted that Tetralin operates via hydride transfer, at least in its reduction of quinones. Thus it has been shown that Tetralin readily donates hydrogen to electron-poor systems, such as quinones at 50°-160°C. The reaction is accelerated by electron-withdrawing substituents on the H-acceptor and polar solvents, and is unaffected by free radical initiators (6). These observations are consistent with hydride transfer, as is the more recent finding of a tritium isotope effect for the reaction (7). [Pg.304]

The product-forming steps of dehalogenations by free radical pathways were discussed earlier (see Section 18.3.1.1). In non-radical mechanisms, the dehalo-genated products (RH) will be formed mostly by reductive elimination [193, 194] however, concerted processes lead directly from RX to RH (see Sections 18.3.1.2 and 18.3.1.3). [Pg.539]

While reduction is usually best carried out using alkaline sodium borohydride, this reaction proceeds by free radicals and is not stereospecific. By employing Na(Hg) in D2O, reduction with retention is observed. However, the stereospecific reduction of (3-hydroxymercurials in which the mercury moiety is a to a carbonyl group has been reported using alkaline NaBH4-EtOH,316 alkaline H2S317 and HS(CH2>3SH (equation 218).316... [Pg.303]

In 2005, Wood and co-workers reported a conceptionally new version of the Barton-McCombie reaction by using water as hydrogen-atom source for the reduction of free radicals in the presence of trialkylboranes (Scheme 35) [85]. [Pg.115]

The present work reports such an approach with the synthesis of (vinyl)polystyrene polyHIPEs and their functionalisation by free radical addition of thiols to the remaining unsaturations. The interest of such materials is proven by the presentation of an application of a thiol functional support in free radical reduction of alkyl halides. [Pg.126]

Chiral polymer-supported thiiranes 401 were prepared by free radical copolymerization of TMA ((3)-thiiranylmethyl-methacrylate) and ethylene glycol dimethacrylate (EDMA) (Equation 60) <2006TA1944>. These chiral thiiranes were transformed into polymer-supported aminothiols by the facile ring opening of the thiirane group with benzylamine and methylamine. These derivatives, complexed with [RuCl2(p-cymene)]2, were used in assymmetric reduction of acetophenone to gave (A)-l-phenylethanol (39% ee from methylamine and 50% ee from benzylamine derivatives). [Pg.382]

In the past 10 years other reductants of the C— Hg bond have been used, mainly thiols and sodium amalgam. Reduction with hydrogen sulfide, sodium dithionite, metals,alcohols, alkaline aqueous bases, aromatic amines, Wilkinson s catalyst and electrochemical reductions have also been described. Organomercurials react with thiols by free radical substitutions with an 5h2 mechanism (Scheme 34). The reaction between PhSH and A -hexenylmercury chloride initiated by light or AIBN gives a mixture of 1-hexene and methylcyclopentane. ... [Pg.857]

The mechanism for reduction of alkyl halides is not always nucleophilic substitution. For example, reductions with organotin hydrides generally " take place by free-radical mechanisms,as do those with Fe(CO)5. Alkyl halides, including fluorides and polyhalides, can be reduced with magnesium and a secondary or ter-... [Pg.1828]

The reduction of alkyl halides by solutions of dissolved metals like, e.g. sodium in ammonia or alkali metal naphthalenides in tetrahydrofuran, provides a convenient means of removing halogens to produce hydrocarbons or to prepare alkali metal organic compounds. It is generally accepted that these reductions involve free radical intermediates R pathway A, Scheme 12) . [Pg.741]


See other pages where Reduction by Free Radicals is mentioned: [Pg.540]    [Pg.87]    [Pg.540]    [Pg.87]    [Pg.526]    [Pg.251]    [Pg.480]    [Pg.697]    [Pg.6]    [Pg.839]    [Pg.567]    [Pg.214]    [Pg.183]    [Pg.214]    [Pg.840]    [Pg.441]    [Pg.576]    [Pg.85]    [Pg.440]    [Pg.143]    [Pg.938]    [Pg.5]    [Pg.655]    [Pg.31]    [Pg.66]    [Pg.211]    [Pg.288]    [Pg.133]    [Pg.543]    [Pg.6]    [Pg.27]    [Pg.70]    [Pg.558]    [Pg.467]    [Pg.128]    [Pg.40]    [Pg.229]   


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Free radicals reduction

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