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El radical nitroxilo más las reacciones de pseudo autointercambio de hidroxilamina: túnel en la transferencia de
Adam Wu1, Elizabeth A Mader, Ayan Datta
1Department of Chemistry, Campus Box 351700, University of Washington, Seattle, Washington 98195-1700, USA.
Journal of the American Chemical Society
|July 22, 2009
Resumen
Las reacciones de transferencia de átomos de hidrógeno entre las hidroxilaminas y los radicales nitroxilo muestran efectos de isótopos cinéticos significativos, lo que indica un papel crucial para el túnel de hidrógeno en estos procesos. Estos hallazgos arrojan luz sobre los mecanismos de las reacciones radicales.
Área de la Ciencia:
- Química Física es la química física.
- La cinética química es la cinética química.
- Mecanismos de reacción Mecanismos de reacción
Sus antecedentes:
- Las reacciones de transferencia de átomos de hidrógeno (HAT) son fundamentales en la química.
- Los radicales nitroxilo y las hidroxilaminas son especies clave en la química radical.
- La comprensión de los mecanismos HAT es crucial para varios procesos químicos.
Objetivo del estudio:
- Para medir las constantes de velocidad bimoleculares para las reacciones HAT entre hidroxilaminas específicas y radicales nitroxilo.
- Para investigar el papel del túnel de hidrógeno en estas reacciones.
- Explorar la influencia de la estructura molecular en las velocidades y mecanismos de reacción.
Principales métodos:
- Se utilizó la espectrofotometría de flujo detenido UV-vis para monitorear la cinética de la reacción.
- Se determinaron las constantes de velocidad bimolecular y las constantes de equilibrio.
- Los efectos del isótopo cinético (KIE) se midieron utilizando hidroxilaminas etiquetadas con deuterio.
- Se emplearon estudios computacionales utilizando POLYRATE para el análisis teórico.
Principales resultados:
- Se observaron grandes efectos de isótopos cinéticos (k H / k D) que van desde 16 a 23 para las reacciones HAT.
- El análisis de los parámetros de activación (Ea y A) sugiere un importante túnel de hidrógeno.
- Los estudios computacionales confirmaron una importante excavación de túneles y proporcionaron información sobre los efectos estructurales.
Conclusiones:
- El túnel de hidrógeno juega un papel importante en las reacciones HAT estudiadas.
- Los KIEs observados y los parámetros de activación apoyan la importancia del túnel mecánico cuántico.
- Las diferencias estructurales, particularmente la presencia de grupos fenilo, pueden influir dramáticamente en las tasas de reacción y las contribuciones de túnel.
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