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Transformación químicamente reversible de alfa-tocoferol (vitamina E) en su catión fenoxonio controlada
Leodrina L Williams1, Richard D Webster
1Research School of Chemistry, Australian National University, Canberra ACT 0200, Australia.
Journal of the American Chemical Society
|September 30, 2004
Resumen
El alfa-tocoferol (alfa-TOH) se somete a una oxidación electroquímica reversible a un catión de fenoxonio estable. Sus productos de oxidación, incluidos los radicales catiónicos y los dications, se caracterizaron utilizando métodos electroquímicos y espectroscópicos avanzados.
Área de la Ciencia:
- La electroquímica es electroquímica.
- Química orgánica es la química orgánica.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- El alfa-tocoferol (alfa-TOH), una forma de vitamina E, es un antioxidante muy importante.
- Comprender su comportamiento electroquímico es clave para dilucidar sus funciones biológicas y sus aplicaciones potenciales.
- Estudios anteriores han explorado las propiedades redox de la vitamina E, pero la caracterización detallada de sus especies catiónicas oxidadas sigue siendo un área de interés.
Objetivo del estudio:
- Para investigar las vías de oxidación electroquímica del alfa-tocoferol (alfa-TOH) en el acetonitrilo.
- Para identificar y caracterizar las especies catiónicas resultantes, incluidos el catión de fenoxonio, el radical catiónico y la dication.
- Determinar la estabilidad y las propiedades de estas formas oxidadas bajo diferentes condiciones.
Principales métodos:
- Técnicas electroquímicas: Voltametría cíclica y electrólisis de potencial controlado.
- Análisis espectroscópicos in situ: espectroscopia UV frente a NIR, FTIR, EPR y RMN.
- Oxidación electroquímica realizada en acetonitrilo con electrolito Bu(4) NPF(6) y diferentes concentraciones de ácido trifílico (CF(3) SO(3) H).
Principales resultados:
- El alfa-tocoferol (alfa-TOH) se oxida electroquímicamente a través de un proceso reversible de dos electrones / un protón a un catión de fenoxonio estable (alfa-TO(+)) a 243 K.
- En presencia del ácido trifílico, el alfa-TO (((+) existe en equilibrio con el radical catiónico alfa-tocoferol (alfa-TOH (((+) ((*)).
- En concentraciones más altas de ácido trifílico, el alfa-TOH se oxida a alfa-TOH (((+) ((*) y posteriormente a la dicción alfa-tocoferol (alfa-TOH (((2+)).
Conclusiones:
- El estudio caracterizó con éxito la oxidación electroquímica del alfa-tocoferol (alfa-TOH) y sus derivados catiónicos.
- El catión fenoxonio (alfa-TO(+)) es un intermediario estable, con su equilibrio influenciado por la concentración de ácido.
- Estos hallazgos proporcionan información fundamental sobre la química redox del alfa-tocoferol, relevante para los mecanismos antioxidantes y la síntesis química.
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