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Estudios mecanicistas de la producción de estireno en un solo paso utilizando un catalizador de rodio

Benjamin A Vaughan¹, Sarah K Khani², J Brannon Gary²

¹Department of Chemistry, University of Virginia , Charlottesville, Virginia 22904, United States.

Journal of the American Chemical Society

|January 21, 2017

Resumen

Este estudio revela vías de reacción competidoras para la síntesis de estireno utilizando un catalizador Rh (I). Las investigaciones mecanicistas muestran dependencias de velocidad variables y efectos de isótopos cinéticos, lo que sugiere un comportamiento catalítico complejo.

Área de la Ciencia:

Química organometálica
Catálisis
Mecanismos de reacción

Sus antecedentes:

El estireno es un químico industrial clave.
Los métodos catalíticos eficientes para la síntesis de estireno son muy buscados.
En trabajos anteriores se informó de una conversión directa de benceno y etileno en estireno catalizada por Rh (I).

Objetivo del estudio:

Para aclarar el mecanismo de reacción de la conversión directa catalizada por Rh (I) de benceno y etileno en estireno.
Investigar las dependencias cinéticas y los intermedios implicados en el ciclo catalítico.
Proporcionar una comprensión completa de las vías de reacción en competencia.

Principales métodos:

Enfoques experimentales y computacionales combinados.
Estudios cinéticos con diferentes concentraciones de catalizador, etileno y oxidante.
Mediciones del efecto isotópico cinético (KIE).
Cálculos de la teoría funcional de la densidad (DFT) (implicado por el enfoque computacional).

Principales resultados:

La velocidad de reacción exhibe una dependencia compleja de la concentración del catalizador (entre el primer y el medio orden).
La concentración de etileno muestra una dependencia de primer orden con saturación a niveles más altos.
La concentración del oxidante Cu (II) tiene una dependencia de orden cero.
Se observaron efectos de isótopos cinéticos (kH/kD = 6,76) en el régimen de primer orden, lo que indica la activación del enlace C-H.

Conclusiones:

Se proponen dos vías catalíticas competidoras: una que involucra intermedios Rh monoméricos y otra que involucra un intermedio Rh binuclear.
Los conocimientos mecanicistas obtenidos pueden orientar el desarrollo de catalizadores de síntesis de estireno más eficientes.
La comprensión de estas vías de competencia es crucial para optimizar el rendimiento y la selectividad del catalizador.

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