Kinetics and mechanism of self-protonation reactions in organic electrochemical processes

Amatore, Christian; Capobianco, G.; Farnia, G.; Sandonà, Giancarlo; Savéant, Jean Michel; Severin, Maria Gabriella; Vianello, E.

doi:10.1021/ja00293a003

Cited by 163 publications

(122 citation statements)

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“…3). Table 2 shows that the experimental value of ∂E p /∂log v is quite similar to theoretical values predicted for both the ECE and DISP1 mechanisms [19].…”

Section: The Electrochemical Reduction Of Phthiocolsupporting

confidence: 70%

“…In this case, the molecule of phthiocol, which contains an acidic group (¹OH), acts itself as a proton donor. Such as in the case of other hydroxysubstituted quinones [16,18], this result can be also interpreted by an ECE-DISP1-DISP2 self-protonation mechanism [16,18,19]. The ECE mechanism corresponds to the sequence of reactions 8, 9, 10 and 11, and the DISP1 or DISP2 mechanism corresponds to the sequence of reactions 8, 9, 10 0 and 11.…”

Section: The Electrochemical Reduction Of Phthiocolmentioning

confidence: 61%

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Cyclic Voltammetry of Two Analogue K-Group Vitamin Compounds in Dimethylsulfoxide

González

1998

Electroanalysis

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The electrochemical reduction of two analogue K-group vitamin compounds, menadione and phthiocol, was studied by cyclic voltammetry in DMSO on glassy carbon electrodes. The reduction process of the more biologically active of these compounds (menadione), is associated with the formation of the semiquinone anion radical and the dianion. Two separated reversible one-electron peaks were observed. In contrast, the less biologically active phthiocol exhibits a single irreversible 2/3-electron peak which is explained by an ECE-DISP1 self-protonation mechanism. In the presence of a donor proton such as benzoic acid, menadione and phthiocol are reduced both through a sequence of consecutive electron transfer and protonation reactions occurring via an irreversible two-electron ECE-DISP1 mechanism.

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“…3). Table 2 shows that the experimental value of ∂E p /∂log v is quite similar to theoretical values predicted for both the ECE and DISP1 mechanisms [19].…”

Section: The Electrochemical Reduction Of Phthiocolsupporting

confidence: 70%

Section: The Electrochemical Reduction Of Phthiocolmentioning

confidence: 61%

Cyclic Voltammetry of Two Analogue K-Group Vitamin Compounds in Dimethylsulfoxide

González

1998

Electroanalysis

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“…As it has been previously described for -hydroxyquinones (Q-OH), the first reduction occurs as a 2/3 electron per mole of quinone transfer process, [13][14][15] where self-protonation reactions 16 consume the semiquinone formed during the first electron transfer process via ECE/DISP reactions (equations 3-7). This is due to the higher acidity of the enolic -hydroxy function compared to the -hydroxy group.…”

Section: Acidity Level Of the Oh Functionality And The Electrochemicamentioning

confidence: 99%

The role of intramolecular hydrogen bonding in the electrochemical behavior of hydroxy-quinones and in semiquinone stability

Frontana¹,

González²

2005

J. Braz. Chem. Soc.

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O estudo de um grupo selecionado de e -hidroxiquinonas ([ ] 2-hidroxi-1,4-naftoquinona 2HNQ, [ ] 5-hidroxi-1,4-naftoquinona 5HNQ and [ , ]5,8-dihidroxi-1,4-naftoquinona DHNQ) mostrou que ambos os tipos de funcionalidades diferem consideravelmente em termos de reatividade eletroquímica e química, e que essas diferenças também se manifestam na comparação de compostos do mesmo grupo. Os resultados provaram que a energia necessária para reduzir eletroquimicamente as hidroxoquinonas estudadas está relacionada com a estabilidade intramolecular das ligações de hidrogênio (IHBs) e com as reações de acoplamento que ocorrem durante a redução eletroquímica, tal como a seqüência de auto-protonação em 2HNQ. A análise da cinética de transferência de elétron associada com a redução monoeletronica que ocorre para 5HNQ e DHNQ mostraram que os efeitos IHB não afetam a cinética do primeiro processo de redução, mas induzem a grandes mudanças na cinética de segunda transferência eletrônica. Isso sugere que as semiquinonas são quimicamente diferentes dos compostos estudados, o que foi comprovado pela análise da estrutura eletrônica das semiquinonas por espectroscopia ESR. Essa análise parece relacionada com a perda de simetria no radical gerado eletronicamente e induz a valores ks de menor velocidade para a segunda redução de transferência de 5HNQ, comparada com DHNQ.The study of a selected group of and -hydroxyquinones ([ ] 2-hydroxy-1,4-naphthoquinone 2HNQ, [ ] 5-hydroxy-1,4-naphthoquinone 5HNQ and [ , ]5,8-dihydroxy-1,4-naphthoquinone DHNQ) showed that both type of functionalities differ considerably in terms of electrochemical and chemical reactivity, and these differences are also manifest even upon comparison between compounds of the same group. The results proved that the energy needed to electrochemically reduce the studied hydroxyquinones is related both to the stability of intramolecular hydrogen bonds (IHBs) and coupled chemical reactions occurring during their electrochemical reduction such as self-protonation sequences in 2HNQ. The analysis of the electron transfer kinetics associated with the monoelectronic reductions occurring for 5HNQ and DHNQ showed that IHB effects do not affect the kinetics of the first reduction process, but induce great changes in the second electron transfer kinetics. This suggests that semiquinone species are chemically different for the studied compounds, as was corroborated by the analysis of the electronic structure of semiquinone species by ESR spectroscopy. This analysis seems to be related to the loss of symmetry in the electrogenerated radical and induces a lower rate ks value for the second reduction transfer of 5HNQ, compared with DHNQ.

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“…La mesure de la largeur de pic pour diffkrentes vitesses de balayage (0,l-25 V s-I) fournit une valeur moyenne EpI2 -Ep = 58 mV. L'ensemble de ces rCsultats est en accord avec un processus de type ECE,, ou DISP 1 (17). L'absence de rCversibilitt ne pennettant pas de definir la valeur de E, pour le systkme BCOH/BCOH;, il est difficile de prCciser lequel des deux mkcanismes intervient dans ce cas.…”

Section: Resultats Et Discussionunclassified

Réduction électrochimique régiosélective d'aroyl-2- ou d'acetyl-2 chromones en milieu non aqueux

Boutoute¹,

Mousset²

1992

Can. J. Chem.

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Kinetics and mechanism of self-protonation reactions in organic electrochemical processes

Cited by 163 publications

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Cyclic Voltammetry of Two Analogue K-Group Vitamin Compounds in Dimethylsulfoxide

Cyclic Voltammetry of Two Analogue K-Group Vitamin Compounds in Dimethylsulfoxide

The role of intramolecular hydrogen bonding in the electrochemical behavior of hydroxy-quinones and in semiquinone stability

Réduction électrochimique régiosélective d'aroyl-2- ou d'acetyl-2 chromones en milieu non aqueux

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