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Un estudio espectroscópico del análogo de nicotina 2-fenilpirrolidina (PPD) utilizando ionización resonante de dos
Danielle E Martin1, Evan G Robertson, Jonathan G MacLellan
1School of Chemistry, Monash University, Victoria 3800, Australia.
Journal of the American Chemical Society
|February 6, 2009
Resumen
Las preferencias de conformación de la 2-fenilpirrolidina (PPD) difieren entre las fases de gas y solución. El transformador-conformador domina en la fase gaseosa, mientras que los conformadores cis prevalecen en la solución debido a los efectos del disolvente.
Área de la Ciencia:
- Química Física es la química física.
- Química computacional es la química computacional.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Los análogos de la nicotina como la 2-fenilpirrolidina (PPD) exhiben comportamientos conformacionales complejos.
- Comprender estas preferencias es crucial para los estudios de la relación estructura-actividad.
Objetivo del estudio:
- Investigar las preferencias conformacionales de la 2-fenilpirrolidina (PPD) tanto en la fase de gas como en la de solución.
- Para dilucidar la influencia del entorno de fase en la conformación molecular.
Principales métodos:
- Cálculos teóricos de alto nivel (MP2, B3LYP) para predecir los conformes estables.
- Espectroscopia de ionización resonante de dos fotones (R2PI) para el análisis de la fase gaseosa.
- Espectroscopia de microondas para la determinación precisa de la estructura de la fase gaseosa.
- Espectroscopia de resonancia magnética nuclear de protones 1D y 2D para estudios de la fase de solución.
- Cálculos teóricos basados en disolventes para modelar el comportamiento de la solución.
Principales resultados:
- Los cálculos teóricos identificaron 5-6 conformadores estables de la PPD, que difieren en la torsión, la inversión y el arrugamiento del anillo.
- La R2PI de fase gaseosa y la espectroscopia de microondas confirmaron el dominio de un solo transformador, consistente con las predicciones teóricas.
- La RMN de la fase de solución (1) H reveló una marcada preferencia por los cisconformes.
- Los cálculos basados en disolventes apoyaron la mayor estabilidad de los conformadores cis en entornos de solución simulada (cloroformo, agua).
Conclusiones:
- La preferencia conformacional de la PPD es muy dependiente de la fase.
- Una interacción estabilizadora N...H...ortho) favorece al transformador en la fase de gas.
- Las interacciones con disolventes interrumpen esta interacción, lo que lleva a la prevalencia de conformadores cis en la solución.
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