Metal complexes as antioxidants. 8. A kinetic and product study of the reaction of tertiary alkylperoxy radicals with cobalt(II) acetylacetonate

Howard, J. A.; Tong, S. B.

doi:10.1139/v80-311

Cited by 10 publications

(8 citation statements)

References 5 publications

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“…We did, however, investigate the products of this reaction and found that thermolysis of a-cumyl hyponitrite (22 mM) in chlorobenzene containing VO(acac), (40 mM) at 303 K for 4 days gave a-cumyl alcohol (25 mM), acetophenone (2 mM), a-methylstyrene (3.2 mM), and chlorotoluene (2 mM); acetylacetone was not formed although there was a significant yield of 4-hydroxypentan-2-one. The ratio AIK was -14 which is considerably higher than the ratio obtained from reaction of cumylperoxyl with VO(acac), and is very similar to the ratio obtained from reaction of PhCMe20a with Co-(acac), (11). The residue which remained after removing the solvent and volatile reaction products was dissolved in chlorobenzene and the esr spectrum showed that VO(acac), (-20 mM) had been regenerated.…”

Section: Curnyloxylsupporting

confidence: 64%

A kinetic electron spin resonance study of the reaction of some oxy radicals with vanadyl acetylacetonate

Howard¹,

Tait²,

Yamada³

et al. 1981

Can. J. Chem.

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. Can. J . Chem. 59, 2184Chem. 59, (1981.Reactions of phenoxyl, iminoxyl, nitroxyl, peroxyl, and alkoxyl radicals with VO(acac), in solution have been studied by kinetic esr spectroscopy. Rates of reaction are first-order with respect to each reactant and radical reactivity increases in the order galvinoxyli 2,4,6-tri-tert-butylphenoxyl< di(l-adamanty1)methylene-iminoxyl< tert-butylperoxyl. Rates of reaction are retarded by pyridine and accelerated by methanol and there is an isotope effect on the rate when the hydroxyl proton of C H 3 0 H is replaced by deuterium. Vanadium-5 I nmr spectroscopy has demonstrated that several vanadium(V) products are formed while conventional product studies have indicated that, in the case of phenoxyl and alkoxyl, the radical is reduced almost exclusively to the parent phenol and alcohol and that VO(acac), is eventually regenerated in substantial yields. The net reaction is, therefore, catalytic reduction of the radical. Variable temperature esr studies have shown that phenoxyl and iminoxyl radicals and VO(acac), exist in equilibrium with diamagnetic reaction products. Utilisant la spectroscopie de rpe cinktique, on a etudie les reactions des radicaux phenoxyle, iminoxyle, nitroxyle, peroxyle et alkoxyle avec le VO(acac), en solution. Les vitesses de reaction sont du premier ordre par rapport a chaque rkactifet la reactivite des radicaux augmente dans I'ordre suivant: galvinoxyle < tri-tert-butyl-2,4,6 phenoxyle < di(adamanty1-1) methylhe iminoxyle < tert-butylperoxyle. Les vitesses de reaction sont ralenties par la pyridine et accelCrees par le methanol et le remplacement du proton hydroxylique du C H 3 0 H par un deuterium provoque un effet isotopique cinttique. La spectroscopie de rmn du vanadium-51 a demontre qu'il se forme plusieurs produits du vanadium(V) tandis que des etudes conventionnelles des produits indiquent que, dans le cas du phenoxyle et de I'alkoxyle, le radical est presqu'exclusivement reduit en phenol apparente et en alcool alors que le compose VO(acac), est regenere avec des rendements qui sont eventuellement substantiels. La reaction globale est cependant une reduction catalytique du radical. Des etudes de rpe ti temperature variable rtvelent que les radicaux phenoxyle et iminoxyle et le VO(acac), existent en equilibre avec des produits de reaction diamagnetiques.[Traduit par le journal] Introduction to give a vanadium(V)-ROOH complex which is ~t is well known that oxidation of olefins, Sul-followed by nucleophilic attack at the "activated" phides, sulphoxides, and amines by alkyl hydro--0-0-bond of the hydroperoxide by the peroxides (ROOH) is catalyzed by vanadyl acetyl-nucleo~hile. acetonate, VO(acac), (1).Although these oxidations are heterolytic there is some evidence that free-radicals are produced by

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Section: Curnyloxylsupporting

confidence: 64%

A kinetic electron spin resonance study of the reaction of some oxy radicals with vanadyl acetylacetonate

Howard¹,

Tait²,

Yamada³

et al. 1981

Can. J. Chem.

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“…The mechanism of the reaction of peroxyl radical with manganese(II)-(3,5-DIPS) 2 differs from the other chelates in that manganese(II) also reacts to remove alkylbenzeneperoxyl radical according to following reduction process [13,[35][36][37]:…”

Section: Anti-oxidantmentioning

confidence: 99%

Anti-oxidant and pro-oxidant reactivities of copper(II), manganese(II) and iron(III) 3,5-di-i-propylsalicylate chelates during peroxidation of alkylbenzenes

Tavadyan

Sedrakyan

Minasyan

et al. 2004

Transition Metal Chemistry

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Bioactive copper(II), iron(III), and manganese(II) 3,5-di-i-propylsalicylate (3,5-DIPS) chelates were investigated in order to determine their ability to inhibit the free radical initiated chain reactions leading to the peroxidation of isopropylbenzene (i-PrPh) and ethylbenzene (EtPh). Quantitative kinetic studies of these chelates established the following order of anti-oxidant reactivities: manganese(II)-(3,5-DIPS) 2 > iron(III)(3,5-DIPS) 3 > copper(II) 2 (3,5-DIPS) 4 >> 3,5-DIPS acid. The mechanism of anti-oxidant reactivity of these three chelates is established as being due, in part, to their chain-breaking capacity resulting from the chemical reduction of the generated peroxyl radical to yield alkybenzenelhydroperoxides via reaction of the 3,5-DIPS ligand with the peroxyl radical. In the case of manganese(II)3,5-di-i-propylsalicylate, the central metalloelement also interacts with the peroxyl radical. The manganese(II)-(3,5-DIPS) 2 and copper(II) 2 (3,5-DIPS) 4 chelates were also found to exhibit alkylhydroperoxide prooxidative reactivity leading to the formation of the alkylbenzeneperoxyl radical. In addition, the manganese(II) atom underwent oxidation to manganese(III) with the formation of the alkylbenzenehydroperoxide or superoxide with air oxygen oxidation. Amyl acetate and dipropylamine (n-Pr 2 NH) were added to the reaction mixture to model the biochemical presence of ester or amine cellular components. Addition of amyl acetate to the reaction mixture increased the anti-oxidant reactivity of manganese(II)-(3,5-DIPS) 2 while decreasing its pro-oxidant reactivity. The weaker anti-oxidant reactivites of iron(III)(3,5-DIPS) 3 and copper(II) 2 (3,5-DIPS) 4 were less affected by the addition of amyl acetate and the pro-oxidant reactivity of copper(II) 2 (3,5-DIPS) 4 was not changed by the addition of amyl acetate, while the pro-oxidant property of iron(III)(3,5-DIPS) 3 was eliminated. In contrast to 2,6-di-t-butyl-4-methylphenol, butylated hydroxy toluene (BHT), anti-oxidant reactivities of copper(II), iron(III), and manganese(II) 3,5-DIPS chelates were dramatically enhanced by the addition of n-Pr 2 NH to the reaction mixture. It is concluded that all three metalloelement chelates react with and remove alkylbenzeneperoxyl radicals and the hydroperoxyl radical. The manganese(II)-(3,5-DIPS) 2 and copper(II) 2 (3,5-DIPS) 4 chelates may also be useful in removing hydroperoxides in vivo. These reactivities, in addition to their established superoxide dismutase (SOD)-mimetic and catalase-mimetic reactivities, are suggested to possibly permit anti-oxidant and pro-oxidant reactivities in aqueous and organic cellular compartments.

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“…• with Co(II)(acetylacetonate) 2 , as well as Mn(II)(1,10-phenanthroline)(stearate) 2 , Co(II)(1,10-phenanthroline)(stearate) 2 , and Mn(II)(3,5-di-isopropylsalicylate) 2 [18][19][20][21][22]. Values smaller than 1 for f R are described for the formation of free radicals along with nonradical products formed with the removal of tert-butylOO…”

Section: Mechanism Of Tert-butyloomentioning

confidence: 99%

Reactivity of tert‐butylperoxyl radical with manganese(III), cobalt(II), and nickel(II) salicylidene Schiff base chelates

Tavadyan

Tonikyan

Musaelyan

et al. 2007

Int J of Chemical Kinetics

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ethylenediaminonickel(II), and N,N -bis(salicylidene)ethylenediaminoaquacobalt(II), as well as (R,R)-(-)-N,N -bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine, were kinetically examined as antioxidants in the scavenging of tert-butylperoxyl radical (tert-butylOO • ). Absolute rate constants and corresponding Arrhenius parameters were determined for reactions of tert-butylOO• with these chelates in the temperature range −52.5 to −11 • C. High reactivity of tert-butylOO• with Mn(III) and Co(II) salicylidene Schiff base chelates was established using a kinetic electron paramagnetic resonance method. These salicylidene Schiff base chelates react in a 1:1 stoichiometric fashion with tert-butylOO

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Metal complexes as antioxidants. 8. A kinetic and product study of the reaction of tertiary alkylperoxy radicals with cobalt(II) acetylacetonate

Cited by 10 publications

References 5 publications

A kinetic electron spin resonance study of the reaction of some oxy radicals with vanadyl acetylacetonate

A kinetic electron spin resonance study of the reaction of some oxy radicals with vanadyl acetylacetonate

Anti-oxidant and pro-oxidant reactivities of copper(II), manganese(II) and iron(III) 3,5-di-i-propylsalicylate chelates during peroxidation of alkylbenzenes

Reactivity of tert‐butylperoxyl radical with manganese(III), cobalt(II), and nickel(II) salicylidene Schiff base chelates

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