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La unión de aminas orgánicas protonadas con poliéteres cíclicos: su importancia en los procesos de transporte
Science (New York, N.Y.)
|March 3, 1978
Resumen
El poliéter cíclico 18-corona-6 forma complejos con aminas protonadas. La estabilidad del complejo disminuye con el aumento de la protonación de aminas, en correlación con la permeabilidad de la membrana, impulsada por cambios de entalpía.
Área de la Ciencia:
- Química supramolecular de las moléculas.
- Química Física es la química física.
- Química biofísica y bioquímica.
Sus antecedentes:
- Los poliéteres cíclicos como el 18-crown-6 son conocidos por su capacidad para cationes complejos.
- Las aminas protonadas juegan un papel crucial en los sistemas biológicos y en los procesos químicos.
- La comprensión del comportamiento de complicación es clave para las aplicaciones en el transporte de iones y la detección.
Objetivo del estudio:
- Para investigar la complejación de 18-corona-6 con varias aminas protonadas en el metanol.
- Para correlacionar la estabilidad de estos complejos con la permeabilidad de las aminas protonadas a través de las membranas biológicas.
- Para dilucidar las fuerzas motrices termodinámicas detrás de las tendencias de complejidad observadas.
Principales métodos:
- Titulación espectrofotométrica para determinar las constantes de formación (log K) de 18-corona-6 con aminas protonadas.
- Análisis de los parámetros termodinámicos (cambios de entalpía y entropía) para la formación de complejos.
- Comparación de datos complejos de estabilidad con los datos existentes de permeabilidad de la membrana.
Principales resultados:
- Las constantes de formación (log K) para complejos de 18 coronas-6 con aminas protonadas disminuyen en el orden NH4+, RNH3+ > R2NH2+ > R3NH+.
- Este orden de estabilidad refleja las secuencias de permeabilidad previamente observadas para las aminas orgánicas protonadas a través de las bicapas lipídicas y las membranas biológicas.
- El factor principal que influye en la disminución de los valores de log K es una reducción en el cambio de entalpía (ΔH), mientras que el término de entropía (TΔS) permanece relativamente constante.
Conclusiones:
- 18-corona-6 exhibe complejación selectiva con aminas protonadas, con una estabilidad inversamente relacionada con el grado de protonación de aminas.
- La tendencia de complejidad observada proporciona una base termodinámica para comprender la permeabilidad de las aminas protonadas a través de las membranas.
- El cambio de entalpia es el contribuyente dominante a las diferencias de estabilidad observadas en estos complejos supramoleculares.
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