Semiempirical and ab initio conformational analysis of 2-methylene-8,8-dimethyl-1,4,6,10-tetraoxaspiro[4.5] decane with application of GIAO-SCF methods to NMR spectrum interpretation.
J Mol Graph Model
; 18(6): 567-80, 2000 Dec.
Article
en En
| MEDLINE
| ID: mdl-11155313
The GIAO-SCF method for calculating isotropic nuclear magnetic shielding values has been utilized to explain certain features in the 1H-NMR spectrum of 2-methylene-8,8-dimethyl-1,4,6,10-tetraoxaspiro[4.5] decane. Population distributions of the low-energy conformers based on their ab initio energies were used to produce weighting factors for the individual calculated shielding values to calculate the weighted average of the shielding values for a complete set of conformers. The differences in 1H chemical shifts between the hydrogens of the two methyl groups and between the axial and equatorial hydrogens in 2-methylene-8,8-dimethyl-1,4,6,10-tetraoxaspiro[4.5] decane were shown to be due to energy differences between the chair and boat orientations of the six-membered ring and contribution from a twist-boat conformation. Results suggest a hypothesis that intramolecular differences in chemical shift might be calculated to a greater degree of accuracy than chemical shifts calculated relative to a standard.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Compuestos de Espiro
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
J Mol Graph Model
Asunto de la revista:
BIOLOGIA MOLECULAR
Año:
2000
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Estados Unidos