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Observación directa de la dinámica de la disolución de ylidos por donantes de enlaces de hidrógeno utilizando
Ryan Phelps1, Andrew J Orr-Ewing1
1School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K.
Journal of the American Chemical Society
|May 17, 2022
Resumen
Los carbenos singlet del diazoacetato de etilo forman ylidos en disolventes, con interacciones estudiadas por espectroscopia ultrarrápida. La dinámica de solvación revela interacciones específicas con los donantes de enlaces de hidrógeno y los cationes de litio.
Área de la Ciencia:
- Química Física
- Espectroscopia
- Química computacional
Sus antecedentes:
- La fotoexcitación de los compuestos α-diazocarbonilo genera intermedios reactivos de carbenos singlet.
- Estos carbenos pueden reaccionar con disolventes nucleófilos para formar ylidos zwitteriónicos, influyendo en las interacciones de disolventes.
- La comprensión de la formación y la solución de ylide es crucial para controlar las vías de reacción de los carbenos.
Objetivo del estudio:
- Investigar las reacciones de formación de ylide de los carbenos singlet intermedios mediante espectroscopia ultrarrápida.
- Caracterización de las siguientes interacciones entre el ylide y el disolvente, incluida la dinámica de la solvación y los efectos de coordinación.
- Para aclarar la competencia entre la formación de ylide y las vías de inserción C-H.
Principales métodos:
- Se utilizó la espectroscopia de absorción infrarroja de resolución ultra rápida para estudiar las reacciones en varios disolventes.
- La fotoexcitación del etil diazoacetato a 270 nm inició la generación de carbenos.
- Se utilizaron cálculos químicos cuánticos (MP2) y simulaciones de dinámica molecular basadas en DFT para el análisis detallado de la interacción.
Principales resultados:
- Se obtuvo evidencia espectroscópica directa de la competencia entre la formación de ylide y la inserción de C-H.
- Se observó una dinámica de disolución específica del ylide derivado del tetrahidrofurano (THF) con donantes de enlaces de hidrógeno y Li+.
- Las bandas de ylide enlazadas con hidrógeno mostraron desplazamientos característicos, y se cuantificaron los efectos de coordinación en la hibridación de carbono ylidic.
Conclusiones:
- La espectroscopia ultrarrápida proporciona una herramienta poderosa para rastrear la formación de ylide y las interacciones de disolventes en tiempo real.
- La solvación y la coordinación catiónica influyen significativamente en la estructura electrónica y la reactividad de los intermedios de yelídeo.
- Los métodos computacionales complementan los datos espectroscópicos, revelando sitios de coordinación preferenciales y cambios electrónicos.
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