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Exploración multidimensional de los puntos de inflexión entre el valle y la cresta en las superficies de energía
April N Sheppard1, Orlando Acevedo
1Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA.
Journal of the American Chemical Society
|February 6, 2009
Resumen
Las reacciones de oxígeno singlet con alquenos pueden proceder a través de un mecanismo escalonado con un intermediario de perepóxido, contrariamente a las suposiciones anteriores. La polaridad del disolvente influye en la estabilidad intermedia y las vías de reacción, revelando nuevos conocimientos sobre este importante proceso químico.
Área de la Ciencia:
- Química Física es la química física.
- Química computacional es la química computacional.
- Mecanismos de reacción orgánica.
Sus antecedentes:
- La reacción de ene que involucra oxígeno singlete ((1) O ((2)) y alquenos es un área bien estudiada.
- Investigaciones anteriores propusieron un mecanismo concertado de "dos pasos sin intermedios" basado en cálculos de la fase gaseosa.
- No se comprendió completamente el papel de los efectos del disolvente en el mecanismo de reacción.
Objetivo del estudio:
- Investigar el mecanismo de la reacción (1)O(2) en fases condensadas.
- Para explorar la influencia de la polaridad del disolvente en la vía de reacción y la estabilidad intermedia.
- Desarrollar y aplicar nuevos métodos computacionales para la construcción de superficies de energía potencial.
Principales métodos:
- Cálculos de potenciales tridimensionales de la fuerza media (3-D PMF) utilizados.
- Empleó simulaciones de mecánica cuántica / mecánica molecular (QM / M).
- Ha realizado cálculos ab initio de alto nivel (CCSD, MP4 y SDQ) con modelos de disolventes (CPCM).
Principales resultados:
- Predijo un mecanismo escalonado que presentaba un intermediario de perepóxido simétrico separado por carga en fases condensadas.
- Se demostró que la polaridad del disolvente tiene un impacto significativo en la estabilidad intermedia y las barreras de activación.
- Demostró que la reducción de la dimensionalidad de la superficie de energía potencial puede conducir a una mala interpretación del mecanismo.
Conclusiones:
- Es probable que la reacción (1)O(2) se produzca mediante un mecanismo escalonado en fases condensadas, con un intermediario de perepóxido.
- Los efectos del disolvente son cruciales y pueden alterar la vía de reacción en comparación con los estudios de la fase gaseosa.
- Un enfoque multidimensional es esencial para la construcción precisa de la superficie de energía potencial y la comprensión mecánica.
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