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Los cálculos de trayectoria para la ciclización de Bergman predicen los efectos de isótopos cinéticos H/D debido a la
Charles Doubleday1, Mayla Boguslav1, Caronae Howell1
1Department of Chemistry, Columbia University , 3000 Broadway, New York, New York 10027, United States.
Journal of the American Chemical Society
|June 10, 2016
Resumen
Este estudio revela cómo las dinámicas no estadísticas de los productos influyen en los efectos cinéticos de los isótopos de hidrógeno y deuterio durante la ciclización de Bergman. La deuteración retrasa el recrudecimiento del producto, alterando los resultados de la reacción y las KIE.
Área de la Ciencia:
- Dinámica Química
- Química orgánica
- Mecanismos de reacción
Sus antecedentes:
- Los efectos de isótopos cinéticos (KIE) son cruciales para comprender los mecanismos de reacción.
- La dinámica no estadística y la redistribución vibratoria intramolecular (RVI) pueden afectar significativamente las vías de reacción.
Objetivo del estudio:
- Para investigar un efecto inusual de isótopo cinético H/D (KIE) en la ciclización de Bergman de (Z) -3-hexeno-1,5-dieno.
- Aclarar el papel de la dinámica no estadística de los productos y el IVR en la determinación de las KIE.
Principales métodos:
- Se emplearon cálculos de trayectoria casi clásicos basados en la Teoría Funcional de Densidad (DFT).
- Las simulaciones analizaron la ciclización de Bergman de (Z) -3-hexeno-1,5-dieno y sus isótopos a 470 K.
- Se examinó la influencia de la incorporación de deuterio en las tasas de IVR y el recrudecimiento de productos.
Principales resultados:
- Se observó que una fracción significativa (28%) de la p-benzina naciente regresaba al precursor de la enediina.
- La deuteración aceleró la RIV en el p-benceno, reduciendo el recrudecimiento y aumentando el rendimiento de los productos estables.
- Los KIE observados se desviaron de las predicciones de la teoría de los estados de transición, destacando la importancia de la dinámica de los estados posteriores a la transición.
Conclusiones:
- Las dinámicas no estadísticas en el producto, específicamente el recrudecimiento, son una fuente primaria de selectividad isotópica en esta reacción.
- Los KIEs convencionales se pueden utilizar para estudiar los procesos de IVR en la ciclización de Bergman.
- La fuga de energía de punto cero vibratorio (ZPE) en la coordenada de reacción no alteró significativamente las KIE pronosticadas.
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