Reactivity of superoxide ion with ethyl pyruvate, .alpha.-diketones, and benzil in dimethylformamide

Sawyer, Donald T.; Stamp, John J.; MENTON, K. A.

doi:10.1021/jo00169a024

Cited by 25 publications

(8 citation statements)

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“…In the case of diacetyl ( 4 ), its reaction with O 2 .− can be expected to follow a similar mechanism that has been proposed for diketones (Scheme ). This might initially involve O 2 .− undergoing a nucleophilic addition at the carbonyl group, followed by another molecule of O 2 .− acting as a one‐electron reductant, subsequently leading to an intramolecular cyclization reaction, and cleavage of the median C−C bond to give carboxylate anions.…”

Section: Resultsmentioning

confidence: 62%

Comparing the Relative Reactivities of Food and Vitamin Molecules Toward Electrochemically Generated Superoxide in Dimethylformamide

et al. 2017

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Superoxide (O2.−), an anionic radical of the reactive oxygen species (ROS) family, is continuously produced in the body and can lead to the undesirable modification and damage of important biological molecules. In the present study, the relative reactivities of 18 food and vitamin molecules toward electrochemically generated O2.− were investigated in N,N‐dimethylformamide (DMF) solutions by using cyclic voltammetry (CV). The quenching of O2.− was measured by monitoring the decreases in the anodic currents of the reverse peaks after the one‐electron reduction of molecular oxygen (O2), while systematically increasing the concentration of the test substrates. The reactivity of each compound was then approximated and compared using effective concentration indexes, EC10 and EC50, which represent the amount of compound required to reduce the concentration of the electrochemically generated O2.− by 10 and 50%, respectively, under the present conditions. Where possible, the likely mechanisms that are involved in the scavenging of O2.− are also discussed.

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Section: Resultsmentioning

confidence: 62%

Comparing the Relative Reactivities of Food and Vitamin Molecules Toward Electrochemically Generated Superoxide in Dimethylformamide

et al. 2017

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“…50 The relatively high spin density distribution and negative charge (as indicated by the NPA charge distribution) on the terminal O of the R-O-O -group may exhibit reactivity similar to that of the O 2 •-ion. In the gas phase as well as in the aqueous solution, [51][52][53] it has been demonstrated that O 2 •- …”

Section: Resultsmentioning

confidence: 99%

Comparative DFT Study of the Spin Trapping of Methyl, Mercapto, Hydroperoxy, Superoxide, and Nitric Oxide Radicals by Various Substituted Cyclic Nitrones

2005

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The thermodynamics of the spin trapping of various cyclic nitrones with biologically relevant radicals such as methyl, mercapto, hydroperoxy, superoxide anion, and nitric oxide was investigated using computational methods. A density functional theory (DFT) approach was employed in this study at the B3LYP/6-31+G(d,p)//B3LYP/6-31G(d) level. The order of increasing favorability for Delta G(rxn) (kcal/mol) of the radical reaction with various nitrones, in general, follows a trend similar to their respective experimental reduction potentials as well as their experimental second-order rate constants in aqueous solution: NO (14.57) < O2*- (-7.51) < *O2H (-13.92) < *SH (-16.55) < *CH3 (-32.17) < *OH (-43.66). The same qualitative trend is predicted upon considering the effect of solvation using the polarizable continuum model (PCM): i.e., NO (14.12) < O2*- (9.95) < *O2H (-6.95) < *SH (-13.57) < *CH3 (-32.88) < *OH (-38.91). All radical reactions with these nitrones are exoergic, except for NO (and O2*- in the aqueous phase), which is endoergic, and the free energy of activation (Delta G) for the NO additions ranges from 17.7 to 20.3 kcal/mol. This study also predicts the favorable formation of certain adducts that exhibit intramolecular H-bonding interactions, nucleophilic addition, or H-atom transfer reactions. The spin density on the nitronyl N of the superoxide adducts reveals conformational dependences. The failure of nitrones to trap NO at normal conditions was theoretically rationalized due to the endoergic reaction parameters.

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“…Higher energetic excitations afford a subsequent (Z)-(E)-isomerization of the free ligand and are responsible for the spectral changes depicted in Figure 3b. Efforts to scavenge O 2 -by competition reactions with benzyl or benzoic anhydride 40 were not successful.…”

Section: Resultsmentioning

confidence: 99%

Optical and Thermal Electron Transfer Activation of Dioxygen by Viologen Dithiolene Metalates

et al. 1997

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Photoinduced electron transfer activation of dioxygen by redoxactive charge-transfer ion pairs of the type {A 2+ [Pt(mnt) 2 ] 2-} (A 2+ ) 2,2′-,4,4′-bipyridinium or cycloalkylated biimidazolium dication; mnt 2-) maleonitriledithiolate) occurs through an optical electron transfer within an ion pair. This affords the primary redox products A •+ and [Pt(mnt) 2 ] -as indicated by laser flash photolysis. Under argon the transients recombine by fast second-order kinetics. Under dioxygen a different behavior is observed. In the case of acceptors with a first reduction potential more positive than -0.6 V back electron transfer prevails. When the potential is more negative however, A •+ reduces O 2 by pseudo-first-order kinetics to generate O 2 •-, while [Pt(mnt) 2 ] -accumulates in the solution. Quantum yields increase with decreasing excitation wavelength. This suggests that internal conversion of the initially populated excited state to the photoreactive ion pair charge-transfer state is more efficient upon excitation to the interligand (π,π*) state (334 nm) than to the metal-to-ligand charge-transfer state (437 or 580 nm). In the latter cases competitive radiationless deactivation Via metalcentered states occurs. The corresponding Ni and Pd complexes do not exhibit any reactivity due to their very short excited state lifetimes. Formation of O 2 •-was proved by ESR spin-trapping techniques. Accumulation of [Pt(mnt) 2 ] -occurs also when instead of irradiating, the reaction is performed in the dark at about 160°C. The activation energy of 108 ( 10 kJ/mol as obtained for the thermal electron transfer from [Pt(mnt) 2 ] 2-to A 2+ corresponds well to the value calculated from the Hush-Marcus model.

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Reactivity of superoxide ion with ethyl pyruvate, .alpha.-diketones, and benzil in dimethylformamide

Cited by 25 publications

References 0 publications

Comparing the Relative Reactivities of Food and Vitamin Molecules Toward Electrochemically Generated Superoxide in Dimethylformamide

Comparing the Relative Reactivities of Food and Vitamin Molecules Toward Electrochemically Generated Superoxide in Dimethylformamide

Comparative DFT Study of the Spin Trapping of Methyl, Mercapto, Hydroperoxy, Superoxide, and Nitric Oxide Radicals by Various Substituted Cyclic Nitrones

Optical and Thermal Electron Transfer Activation of Dioxygen by Viologen Dithiolene Metalates

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