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Concepto mecanicista unificado de la nitratación aromática electrófila: convergencia de resultados computacionales y

Pierre M Esteves¹, José Walkimar De M Carneiro, Sheila P Cardoso

¹Loker Hydrocarbon Research Institute, Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, USA.

Journal of the American Chemical Society

|April 17, 2003

Resumen

La nitratación aromática electrofílica implica tres productos intermedios, incluido un par radical catión-molécula, lo que explica la selectividad del sustrato y la transferencia de oxígeno. Este mecanismo revisado unifica las propuestas anteriores para esta reacción clave.

Área de la Ciencia:

Química Física es la química física.
Química orgánica es la química orgánica.
Química cuántica es la química cuántica.

Sus antecedentes:

La nitratación aromática electrofílica es una reacción orgánica fundamental.
Las propuestas mecanicistas anteriores para la nitratación tienen limitaciones para explicar las observaciones experimentales.
Comprender el mecanismo de reacción es crucial para controlar la selectividad y las reacciones secundarias.

Objetivo del estudio:

Revisar y proponer un mecanismo modificado para la nitratación aromática electrofílica.
Para incorporar nuevos datos experimentales y cálculos químicos cuánticos de alto nivel.
Unificar las propuestas mecanicistas anteriores y mejorar la comprensión de la reacción.

Principales métodos:

Cálculos químicos cuánticos de alto nivel.
Análisis de los datos experimentales disponibles, incluidos los datos de resonancia ciclotrónica iónica (ICR).
Modelado computacional de diagramas de energía potencial y productos intermedios de reacción.

Principales resultados:

Se propone un mecanismo de tres intermedios, que incluye un complejo donante-aceptor de electrones (EDA), un complejo de transferencia de un solo electrón (SET) (par radical catión-molécula) y un complejo sigma (ión arenio).
El complejo EDA explica la baja selectividad de sustrato y la alta selectividad posicional con las sales de nitronio.
El complejo SET explica la transferencia de un solo electrón desde el sistema aromático al NO (((2) ((+)), y el mecanismo se adapta a las reacciones de transferencia de oxígeno.

Conclusiones:

El mecanismo de tres intermedios propuesto proporciona una visión unificada de la nitratación aromática electrófila.
Este mecanismo revisado explica mejor los patrones de selectividad observados y los fenómenos de transferencia de oxígeno.
El estudio mejora la comprensión fundamental de esta importante transformación química.

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