The Role of Intramolecular Hydrogen Bonding in the Electrochemical Behavior of Hydroxy-Quinones and in Semiquinone Stability
The study of a selected group of α and β-hydroxyquinones ([α] 2-hydroxy-1,4-naphthoquinone2HNQ, [β] 5-hydroxy-1,4-naphthoquinone 5HNQ and [β, β]5,8-dihydroxy-1,4-naphthoquinoneDHNQ) showed that both type of functionalities differ considerably in...
| Autores: | , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2005 |
| País: | México |
| Institución: | Universidad Autónoma Metropolitana |
| Repositorio: | Redalyc-UAM |
| OAI Identifier: | oai:redalyc.org:47549202 |
| Acceso en línea: | https://www.redalyc.org/articulo.oa?id=47549202 |
| Access Level: | acceso abierto |
| Palabra clave: | Química ESR quinones semiquinone self protonation cyclic voltammetry |
| Sumario: | The study of a selected group of α and β-hydroxyquinones ([α] 2-hydroxy-1,4-naphthoquinone2HNQ, [β] 5-hydroxy-1,4-naphthoquinone 5HNQ and [β, β]5,8-dihydroxy-1,4-naphthoquinoneDHNQ) showed that both type of functionalities differ considerably in terms of electrochemical andchemical reactivity, and these differences are also manifest even upon comparison between compoundsof the same group. The results proved that the energy needed to electrochemically reduce the studiedhydroxyquinones is related both to the stability of intramolecular hydrogen bonds (IHBs) andcoupled chemical reactions occurring during their electrochemical reduction such as self-protonationsequences in 2HNQ. The analysis of the electron transfer kinetics associated with the monoelectronicreductions occurring for 5HNQ and DHNQ showed that IHB effects do not affect the kinetics of thefirst reduction process, but induce great changes in the second electron transfer kinetics. Thissuggests that semiquinone species are chemically different for the studied compounds, as wascorroborated 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 inducesa lower rate ks value for the second reduction transfer of 5HNQ, compared with DHNQ. |
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