<b>Polarographic Oxidation Potentials of Aromatic Compounds</b>

Pysh, E. S.; Yang, N. C.

doi:10.1021/ja00897a019

Cited by 357 publications

(187 citation statements)

References 0 publications

Supporting

Mentioning

173

Contrasting

Unclassified

Order By: Relevance

“…1.5 mol L-I for benzene, 1.0 mol L-I for toluene, 0.5 mol L-' for m-and pxylene, 0.4 mol L-I for mesitylene, and 0.2 mol L-I for isodurene) and which, in the absence of any other process, could correspond to a static quenching. The curvature is more pronounced when the electron-donating properties of the aromatics increase (the oxidation potentials versus SCE are 2.38, 2.28, 1.88, 1.77, 1.80, and 1.73 V for benzene (20), toluene (20), m-xylene (20,21), p-xylene (21), mesitylene (21), and isodurene (20), respectively). However, no ground state association could be detected in the absorption spectra of the mixture of the two compounds.…”

Section: Dbmbf2 Absorption and Emissionmentioning

confidence: 99%

Unusually strong emission from an exciplex formed between benzenoid solvents and dibenzoylmethanatoboron difluoride. Formation of a triplex

Valat¹,

Wintgens²,

Chow³

et al. 1995

Can. J. Chem.

View full text Add to dashboard Cite

Benzene derivatives give, in cyclohexane solution, a strongly emitting ( a f up to 0.8) excited complex with dibenzoylmethanatoboron difluoride (DBMBF2). The rate constant k,, for the complex formation varies between 3.5 x lo9 and 2.6 x loL0 M-I s-I depending on the benzene derivative, and the complex emission can already be detected at very low concentrations of the aromatics. This behaviour is different from that found in acetonitrile where the DBMBF2 emission disappeared completely before the new emission of the complex could be detected. The position of the complex emission and its lifetime depend upon the redox potential of the aromatics: the lower the latter, the longer the lifetime and the more the emission is red-shifted. The monotonous increase of the lifetime and of the fluorescence quantum yield of the emission with the concentration of the aromatics has been interpreted on the basis of an equilibrium between the exciplex and excited DBMBF2. The equilibrium constant varies with the electron-donating property of the aromatics, from 2.7 for benzene to 560 M-I for isodurene. A decrease in the excited complex lifetime or in its fluorescence quantum yield is observed in some cases when the aromatics concentration is close to that of the pure solvent. Such behaviour is believed to arise from a new equilibrium resulting from the interaction of the exciplex with a second molecule of the aromatics to form triplex species. A detailed kinetic study has been undertaken in case of p-xylene, and the rate constants of all the processes involved in the double equilibrium have been determined. No basic difference is observed in the rate constant for exciplex formation when a single or double equilibrium is assumed; on the other hand, large discrepancies are found in the exciplex deactivation processes, specially for the back reaction from the exciplex to excited DBMBF2. The equilibrium constants between DBMBF? and the exciplex, on one hand, and between the latter and the triplex are 56.6 and 0.68 M-', respectively, when the concentration of p-xylene in cyclohexane is 3.3 M. Can. J. Chem. 73: 1902Chem. 73: -1913Chem. 73: (1995

show abstract

Section: Dbmbf2 Absorption and Emissionmentioning

confidence: 99%

Unusually strong emission from an exciplex formed between benzenoid solvents and dibenzoylmethanatoboron difluoride. Formation of a triplex

Valat¹,

Wintgens²,

Chow³

et al. 1995

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…Cerrelation of voltammetric data with ionization potentials and electron affinities has firmly established that the solution and gas phase energetics are related and to the first approximation, linearly (Refs. [1][2][3][4][5]. A recent application of these ideas has led to the proposal of an "absolute" electrode potential scale (Ref.…”

Section: Introductionmentioning

confidence: 99%

“…Neglecting gas phase entropy effects and solvent surface potential, which are expected to be small, led to eqns. (4) and (5) for the "absolute" potentials for oxidation and reduction, respectively, of a compound. If the potentials for both processes can be measured in the same solution, then the difference in potential, which is independent of the reference scale, is given by eqn.…”

Section: Introductionmentioning

confidence: 99%

Properties of aromatic ions generated at electrodes

Parker¹

1979

Pure and Applied Chemistry

View full text Add to dashboard Cite

-The methods for the measurement of reversible electrode potentials for the formation of rapidly reacting organic ions and radicals are discussed. Second harmonic ac voltammetry gives the most accurate results. Reliable estimates can be made even when the rate of the follow-up reaction precludes the direct measurement. An analysis of the probable error due to the effect of the kinetic step is made. The measurement of rate constants of several representative reactions, the rates of which are too great to be determined by most other electrochemical techniques, have been carried out using potentials measured by second harmonic ac voltammetry. The method is based upon an empirically derived linear relationship between the measured potential and the rate constant for the follow-up reaction. Examples of electron transfer reactions producing intermediates differing substantially in conformation from that of the substrate are discussed.

show abstract

“…To conform that the measured maxima are due to CT absorption pyrene was also included in the comparison. A plot of V,,,,,(DD) vs. V,,,,,(pyrene) is reasonably linear ( r = 0.979) with a slope close to unity (1 .O1 + 0.09) as required (16 The most important observation is that the CT maximum for DD consistently appears at lower energy than that for DH with the same acceptor, indicating that DD should undergo oneelectron oxidation more easily than DH (16,17). This difference, for two compounds having identical .rr electron systems, is consistent with the predictions of current theory on orbital interactions through u bonds (18).…”

Section: Bqmentioning

confidence: 89%

Kinetics and mechanism of oxidation of N,N′-dimethyl-9,9′-biacridanyl by some π acceptors and a one-electron oxidant

Colter¹,

Lai²,

Parsons³

et al. 1985

Can. J. Chem.

View full text Add to dashboard Cite

Oxidation of N,N′-dimethyl-9,9′-biacridanyl (DD) has been investigated as a model for single electron transfer (SET)-initiated oxidation of NADH coenzyme models such as N-methylacridan (DH). Oxidants investigated cover a 1010-fold range of reactivity in acetonitrile and include the π acceptors 1,4-benzoquinone (BQ), 2,6-dichloro-1,4-benzoquinone (DCIBQ), p-chloranil (CA), 2,3-dicyanobenzoquinone (DCBQ), 2,3-dicyano-1,4-naphthoquinone (DCNQ), 2,3-dicyano-5-nitro-1,4-naphthoquinone (DCNNQ), 9-dicyanomethylene-2,4,7-trinitrofluorene (DCMTNF), 9-dicyanomethylene-2,4,5,7-tetranitrofluorene (DCMTENF), 7,7,8,8-tetracyanoquinodimethane (TCNQ), and tetracyanoethylene (TCNE), and the one-electron oxidant tris(2,2′-bipyridyl)cobalt(III), [Formula: see text] The oxidation product is, in every case, N-methylacridinium ion (D+). A mechanism involving a rate-determining electron transfer with simultaneous fragmentation to D+ and N-methyl-9-acridanyl radical (D•) is proposed. This mechanism is supported by the observed dependence of the rate on oxidant reduction potential, by spin-trapping experiments, by kinetic isotope effects in oxidation of 9,9′-dideuterio-DD, and by substituent effects in oxidation of 2,2′- and 3,3′-dimethoxy-DD. The rate of oxidation of DD relative to that of DH is 3.4 × 102 with [Formula: see text] and with the π acceptors varies from ea. 0.3 (BQ) to 8.1 × 104 (DCMTENF). The results rule out a SET-initiated mechanism for oxidation of DH by all of the oxidants studied except TCNQ and DCMTENF.

show abstract

Polarographic Oxidation Potentials of Aromatic Compounds

Cited by 357 publications

References 0 publications

Unusually strong emission from an exciplex formed between benzenoid solvents and dibenzoylmethanatoboron difluoride. Formation of a triplex

Unusually strong emission from an exciplex formed between benzenoid solvents and dibenzoylmethanatoboron difluoride. Formation of a triplex

Properties of aromatic ions generated at electrodes

Kinetics and mechanism of oxidation of N,N′-dimethyl-9,9′-biacridanyl by some π acceptors and a one-electron oxidant

Contact Info

Product

Resources

About