Barrières de Rotation Adjacentes aux Doubles Liaisons Étude Structurale Théorique D'Acides Carboxyliques, Oléfines et Amides, Relaxation Tensionnelle et Déformations Valencielles des Composés Contraints
✍ Scribed by A. Cossé-Barbi; A. Massat; J. E. Dubois
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2010
- Weight
- 864 KB
- Volume
- 94
- Category
- Article
- ISSN
- 0037-9646
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✦ Synopsis
Conformations associated with alkyl groups adjacent to a double bond are studied on five series ofaldehyde, ketone, carboxylic, amide and olmfine ccmpounds. R(C-X)Y with Y-H,OH,Me,N(Me) and XI0 or -2. The number, the relative abundance of conformers and the ieigth of the rotation barriers obtained by the PCILO method are discussed for two series of compounds w i t h neopentyl chains In each case, the eclipsed double bond form competes with one or two skew conformers. For simple flexible compounds, the conformational motion is determined primarily by rotation relaxation. But for compounds with high structural constraints, the relaxation mechanism implies variations in the bond angles. The conformational flexibility is greatly increased and linked to a marked attenuation of the rotation barriers. The valency relaxation of tensions is estimated at between 20 and 30 kilocalories. they are associated with the existence of strong interactions of the two alkyl groups situated in 6 position with regard to each other. The data used, spectroscopic or theoreticalfare based on 14 compounds BuCH2 (C-X) Y and triptyl groups tBu (Me) 2C (C=X) Y. When tho constraints are important,