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Efectos homoanoméricos en heterociclos de seis miembros
Igor V Alabugin1, Mariappan Manoharan, Tarek A Zeidan
1Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390, USA. alabugin@chem.fsu.edu
Journal of the American Chemical Society
|November 13, 2003
Resumen
Este estudio investiga computacionalmente las interacciones homoanoméricas en anillos de seis miembros, revelando patrones orbitales únicos y efectos como los efectos Plough y W en diferentes heterociclos. Estas interacciones, aunque más débiles que los clásicos efectos anoméricos, son significativas bajo ciertas condiciones.
Área de la Ciencia:
- Química computacional es la química computacional.
- Química orgánica es la química orgánica.
- Química cuántica es la química cuántica.
Sus antecedentes:
- El clásico efecto anomérico implica una superposición de órbitas tipo pi.
- Los efectos homoanoméricos en sistemas cíclicos exhiben patrones de interacción orbital distintos debido a las restricciones geométricas.
Objetivo del estudio:
- Investigar computacionalmente las consecuencias estructurales y energéticas de las interacciones homoanoméricas n ((X) --> beta-sigma ((C-Y).
- Para analizar estas interacciones en heterociclos saturados de seis miembros que contienen O, N, S y Se.
Principales métodos:
- Cálculos de la Teoría Funcional de la Densidad (B3LYP).
- Análisis de la órbita de enlace natural (NBO, por sus siglas en inglés).
Principales resultados:
- Se identificó el efecto Plough dominante (pareja aislada axial al enlace ecuatorial) en los oxa-, tia- y selena-ciclohexanos.
- Se observó un efecto W más grande (pareja equatorial solitaria a enlace ecuatorial) en azaciclohexanos.
- La hiperconjugación influye en los enlaces ecuatoriales C-H, mientras que los enlaces axiales muestran interacciones más débiles.
Conclusiones:
- Los efectos homoanoméricos son más débiles que los efectos anoméricos clásicos, pero ganan importancia con el aumento de la capacidad de aceptor sigma-orbital.
- Las interacciones pueden ser cooperativas o anticooperativas, reflejando la simetría de la función de onda y sugiriendo una débil homoaromaticidad sigma / homoantiaromaticidad.
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