Transmission de l'effet de substituant à travers les systèmes insaturés-IV. Utilisation des relations de type Hammett avec les paramètres spectroscopiques i.r. et RMN pour la détermination des conformations de cétones α, β-éthyléniques aromatiques
✍ Scribed by Serge Geribaldi; Marcel Azzaro
- Publisher
- Elsevier Science
- Year
- 1982
- Tongue
- English
- Weight
- 324 KB
- Volume
- 38
- Category
- Article
- ISSN
- 1386-1425
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✦ Synopsis
The i.r. stretching frequencies of the carbonyl group and the chemical shift of the ethylenic proton in three series of aJi-unsaturated ketones, 3-substituted-5,5-dimethyl-2-cyclohexen-1-ones s-trans p-substituted-4-aryl-3-buten-2-ones and p-substituted-3-aryl-5,5-dimethyl-2-cyclohexen-l-ones, have been analysed using correlations with Hammett type substituent constants. The comparison of parameters p of these correlations allows us to obtain quantitative information on the conformation of the last series of ketones. In this series, the dihedral angle between the aromatic ring and the plane of enonic system varies inversely with the resonance donor effect of substituent (0" for p-NH2, 38* for NO2).