Transmission of long-range coupling through three-membered rings: The cyclopropylcarbinyl σ-π coupling
✍ Scribed by Joseph B. Lambert; Elaine Stedman Magyar
- Publisher
- John Wiley and Sons
- Year
- 1973
- Tongue
- English
- Weight
- 460 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
Abstract
Spin information should be passed most effectively from a carbon‐hydrogen bond to the p‐rich carbon‐carbon bond of an adjacent cyclopropane ring when the two bonds are parallel. The existence of such a mechanism is tested in a series of spiro hydrocarbons and epoxides in which four‐bond zigzag (W) couplings are absent. The structure is varied from the ideal parallel‐orbital geometry of spirohexane and the homologous epoxide to the unfavorable staggered‐orbital geometry of spiro[2·5]octane and its epoxide. In the parallel‐orbital situation, a four‐bond non‐W coupling of about 0·2 Hz is found; this coupling is absent in the other geometric situations. The meager ability of the cyclopropyl bonds to pass spin information, when compared to the π‐orbitals in alkenes, is discussed in terms of the electronic structure of cyclopropanes.