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El espectro de absorción ultravioleta del malonaldehído en el agua está dominado por conformaciones estabilizadas por

Xuefei Xu¹, Jingjing Zheng¹, Donald G Truhlar¹

¹Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States.

Journal of the American Chemical Society

|June 18, 2015

Resumen

En el agua, los conformadores de enol de malonaldehído (MA) no quelado son más estables que los quelados. Las conformaciones estabilizadas con disolventes dominan el espectro UV, lo que explica las observaciones experimentales.

Área de la Ciencia:

Química computacional es la química computacional.
Química Física es la química física.
La espectroscopia es una técnica de espectroscopia.

Sus antecedentes:

El malonaldehído (MA) existe en varios isómeros de enol.
Comprender la estabilidad conformacional de MA y los espectros UV es crucial para la investigación química.
La influencia del disolvente en la conformación molecular y las propiedades electrónicas es un área clave de estudio.

Objetivo del estudio:

Para investigar la estabilidad relativa de los isómeros de malonaldehído enol en diferentes entornos.
Para simular y explicar el espectro de absorción ultravioleta (UV) del malonaldehído en las fases gaseosa y acuosa.
Para dilucidar el papel de las conformaciones estabilizadas con disolventes en los desplazamientos espectrales observados.

Principales métodos:

Cálculos de energía libre para ocho isómeros enol de malonaldehído.
Simulación de espectros de absorción UV utilizando la teoría funcional de la densidad (DFT).
Aplicación del modelo de solvación basado en la densidad (SMD) y un modelo de excitación vertical promediado por conjunto.

Principales resultados:

En el agua, dos conformadores de enol s-trans no quelados de MA son más estables que el conformador de enol quelado (CE).
El espectro UV en el agua está dominado por conformaciones estabilizadas por disolventes que no están significativamente pobladas en la fase gaseosa.
El conformador de enol quelado muestra un ligero desplazamiento al rojo en el agua en comparación con la fase gaseosa.

Conclusiones:

Los efectos del disolvente alteran significativamente el paisaje conformacional y la estabilidad de los isómeros de malonaldehído enol.
El espectro UV observado en la solución acuosa ácida se debe principalmente a las conformaciones transitorias estabilizadas por solvente.
Los métodos computacionales explican con precisión los espectros experimentales de absorción UV del malonaldehído en diferentes fases.

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