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Tripleto de difenilcarbenos protegidos por grupos o-Aryl
Kyoko Monguchi1, Tetsuji Itoh, Katsuyki Hirai
1Chemistry Department for Materials, Faculty of Engineering, Mie University, Tsu, Mie 514-8507, Japan.
Journal of the American Chemical Society
|September 24, 2004
Resumen
La fotólisis de los difenilidioazometanos produce principalmente fluorenos a través del ataque de carbenos individuales. Se observaron carbenos triplet a bajas temperaturas, pero las reacciones a temperatura ambiente mostraron diferentes especies transitorias, lo que sugiere vías alternativas para la formación de fluoreno.
Área de la Ciencia:
- La fotoquímica es la fotoquímica.
- Química orgánica es la química orgánica.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Los difenilidiazometanos son precursores de los difenilicarbeno.
- La reactividad de los carbenos es crucial en la síntesis orgánica y la fotoquímica.
- La comprensión de los mecanismos de reacción de los carbenos requiere técnicas avanzadas de caracterización.
Objetivo del estudio:
- Para caracterizar los difenilcarbenos generados fotoquímicamente.
- Para dilucidar el mecanismo de reacción que conduce a la formación de fluoreno.
- Investigar la influencia de las condiciones de reacción y los sustituyentes en el comportamiento de los carbenos.
Principales métodos:
- Fotólisis de difenildiazometanos en varias matrices y soluciones.
- Resonancia de espín de electrones (ESR) y espectroscopia UV/Vis a bajas temperaturas.
- Fotólisis de flash láser (LFP, por sus siglas en inglés) a temperatura ambiente.
- Análisis del producto y estudios cinéticos.
Principales resultados:
- Los fluoruros son los productos exclusivos bajo condiciones típicas.
- La ESR y la espectroscopia UV/Vis identificaron carbenos triplet a bajas temperaturas.
- La LFP a temperatura ambiente reveló diferentes especies transitorias, distintas de las observaciones a baja temperatura.
- Los sustitutos en los anillos de fenilo mostraron un impacto mínimo en la vía de reacción.
Conclusiones:
- La formación de fluoreno probablemente procede a través del ataque de carbenos individuales en el anillo ortofenilo, seguido de desplazamientos de hidrógeno.
- Los carbenos triplet también pueden ser atrapados por el anillo ortofenilo, contribuyendo a la formación de fluoreno.
- Las condiciones de reacción influyen significativamente en las especies de carbenos observadas y en las vías de reacción.
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