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La isomerización en la fase de solución de nitrenos individuales excitados por vibración a 1,2-didehidroazepina

Gotard T Burdzinski¹, Chris T Middleton, Terry L Gustafson

¹Department of Chemistry, Ohio State University Center for Chemical and Biophysical Dynamics, 100 West 18th Avenue, Columbus, OH 43210, USA.

Journal of the American Chemical Society

|November 16, 2006

Resumen

La fotólisis de azidas genera nitreno excitado, formando rápidamente azacicloheptatetraeno caliente. La espectroscopia ultrarrápida capturó esta isomerización del picosegundo, revelando un paso clave en la fotoquímica de la azida.

Área de la Ciencia:

La fotoquímica es la fotoquímica.
La cinética química es la cinética química.
La espectroscopia es una técnica de espectroscopia.

Sus antecedentes:

La fotólisis de azido es una ruta conocida para los intermediarios de nitreno.
La isomerización de los nitrenos a las deshidroazepinas es mecánicamente significativa.
Comprender la dinámica de estas reacciones requiere una resolución temporal avanzada.

Objetivo del estudio:

Para investigar la formación en tiempo real de 1,2-didehidroazepina a partir de la fotólisis del azido.
Para caracterizar la excitación vibratoria de los productos intermedios y productos.
Para determinar la tasa de isomerización en relación con la relajación térmica.

Principales métodos:

Fotólisis del fenilo y el o-bifenilil azido a 270 nm.
Aplicación de la espectroscopia vibratoria ultrarrápida.
Observación en tiempo real de la dinámica de reacción en picosegundos.

Principales resultados:

El nitreno singlete excitado por vibración se forma durante la fotólisis.
Este nitreno se isomeriza a 1,2-didehidroazepina caliente a una velocidad competitiva con la relajación térmica.
Se observó la formación de 1,2-4,6-azacicloheptatetraeno excitado por vibración en cuestión de picosegundos.

Conclusiones:

El estudio proporciona evidencia directa de la rápida isomerización de los nitrenos a las deshidroazepinas.
La espectroscopia ultrarrápida es eficaz para el estudio de especies químicas transitorias.
La dinámica de la fotólisis de azida es más rápida de lo que se resolvió anteriormente.

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