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Transmission of long‐range coupling through three‐membered rings: The cyclopropylcarbinyl σ‐π coupling
Author(s) -
Lambert Joseph B.,
Magyar Elaine Stedman
Publication year - 1973
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270050903
Subject(s) - cyclopropane , chemistry , epoxide , atomic orbital , coupling (piping) , zigzag , ring (chemistry) , crystallography , computational chemistry , molecular physics , physics , materials science , geometry , catalysis , quantum mechanics , organic chemistry , mathematics , metallurgy , electron
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.