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Quimio-regioselectividad en catálisis heterogénea: rutas competitivas para hidrogenaciones C = O y C = C desde un

David Loffreda¹, Françoise Delbecq, Fabienne Vigné

¹Laboratoire de Chimie, UMR CNRS 5182, Ecole Normale Supérieure de Lyon, France. David.Loffreda@ens-lyon.fr

Journal of the American Chemical Society

|January 26, 2006

Resumen

Este estudio desafía la regla de reactividad típica para la hidrogenación catalítica. Los cálculos de la teoría funcional de la densidad muestran que el grupo carbonilo (C = O) está preferentemente hidrogenado sobre el doble enlace carbono-carbono (C = C) en la acroleína en superficies de platino.

Área de la Ciencia:

Catálisis Heterogénea.
Química de las superficies.
Química computacional es la química computacional.

Sus antecedentes:

La reactividad de los enlaces dobles carbono-carbono (C=C) frente a los grupos carbonilo (C=O) en la hidrogenación catalítica de aldehídos insaturados se entiende típicamente por una regla empírica.
Esta regla sugiere que los bonos C=C son más reactivos que los bonos C=O bajo estas condiciones.

Objetivo del estudio:

Para investigar el mecanismo de hidrogenación catalítica de la acroleína en una superficie de platino (Pt(111) utilizando métodos computacionales.
Reevaluar la regla empírica establecida con respecto a la reactividad relativa de los enlaces C=C y C=O en aldehídos insaturados durante la hidrogenación.

Principales métodos:

Se emplearon cálculos de la teoría funcional de la densidad (DFT) para explorar todas las vías de hidrogenación competitivas para la acroleína en Pt111).
El análisis se centró en los mecanismos de reacción, los estados intermedios y los estados de transición.

Principales resultados:

El estudio encontró que la hidrogenación ataca preferentemente el enlace C = O, lo que contradice la regla empírica convencional.
Se identificaron estados precursores metastables para la formación de enlaces O-H, lo que indica un nuevo mecanismo en el que el grupo C = O no está directamente unido a la superficie de platino.

Conclusiones:

El ataque preferencial al enlace C=O se explica por un mecanismo único que involucra vías intermedias distintas de los mecanismos de Langmuir-Hinshelwood y Rideal-Eley.
La selectividad en la hidrogenación de la acroleína en el platino está significativamente influenciada por el paso de desorción de los productos parcialmente hidrogenados, reconciliando los hallazgos computacionales con las observaciones experimentales.

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