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Observación de una sola molécula de una isomerización mecánicamente activada de ciclopropano a trans
Junpeng Wang1, Tatiana B Kouznetsova1, Stephen L Craig1
1Department of Chemistry, Duke University , Durham, North Carolina 27708, United States.
Journal of the American Chemical Society
|August 9, 2016
Resumen
La activación mecanoquímica de los polímeros cis-gem-difluorociclopropano en el tolueno muestra dos transiciones de fuerza. Estas transiciones indican reacciones competidoras, incluida la isomerización al isómero trans, a diferencia del comportamiento en el benzoato de metilo.
Área de la Ciencia:
- Química de los polímeros
- Mecanoquímica
- Ciencias de los materiales
Sus antecedentes:
- Los mecanóforos sufren transformaciones químicas cuando son sometidos a una fuerza mecánica.
- El cis-gem-difluorociclopropano (cis-gDFC) es un mecanóforo cuyo comportamiento se ha estudiado en el benzoato de metilo (MB).
Objetivo del estudio:
- Caracterizar la activación mecanoquímica de los polímeros cis-gDFC en el tolueno utilizando la espectroscopia de fuerza de una sola molécula.
- Comparar el comportamiento de cis-gDFC en tolueno con su comportamiento previamente reportado en MB.
Principales métodos:
- Se empleó la espectroscopia de fuerza de una sola molécula para sondear la respuesta mecanoquímica de los polímeros cis-gDFC.
- Se analizaron las curvas de fuerza frente a la extensión para identificar transiciones distintas indicativas de reacciones químicas.
Principales resultados:
- Se observaron dos transiciones de fuerza distintas en las curvas de fuerza frente a la extensión de polímeros cis-gDFC en tolueno.
- La primera transición se produjo a ~ 1300 pN, consistente con las observaciones anteriores en MB.
- Una segunda transición a ~ 1800 pN indicó la formación parcial del isómero trans-gDFC, revelando vías de reacción competidoras.
Conclusiones:
- La activación mecanoquímica de cis-gDFC en el tolueno implica reacciones competidoras en la meseta de fuerza de ~ 1300 pN.
- Estas reacciones en competencia incluyen la adición de oxígeno a un intermediario diradicaloide y la isomerización al isómero trans-gDFC.
- Los efectos del disolvente, específicamente el uso de tolueno, influyen significativamente en la respuesta mecanoquímica de los polímeros cis-gDFC.
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