Abstract
Two distinct Gibbs free energies of activation (ΔGc‡) have been determined by the dynamic NMR method for simple twisted homomerous overcrowded bistricyclic enes of the bifluorenylidene series: ΔGc‡ = 44 kJ/mol for the conformational inversion (enantiomerization) of 2-i-propyl-bi-9H-fluoren-9-ylidene, and ΔGc‡ = 104 kJ/mol for the E,Z-isomerization of 2,2′-dimethyl-bi-9H-fluorene-9-ylidene. These barriers are not biased by additional steric constraints and reflect the intrinsic dynamic properties of bifluorenylidenes. Mechanisms for the dynamic processes are proposed, based on the experimental evidence and semiempirical PM3 calculations.
Original language | English |
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Pages (from-to) | 75-80 |
Number of pages | 6 |
Journal | Enantiomer |
Volume | 1 |
Issue number | 1 |
State | Published - 1 Dec 1996 |
Externally published | Yes |
Keywords
- Bistricyclic enes
- Chirality
- Conformational behavior
- Dynamic NMR
- Overcrowding
- Semiempirical calculations
ASJC Scopus subject areas
- General Chemistry
- Biochemistry
- General Biochemistry, Genetics and Molecular Biology
- Organic Chemistry