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Carbon‐13 NMR of fluorocyclopropanes
Author(s) -
Brey Wallace S.
Publication year - 2008
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2205
Subject(s) - chemistry , geminal , vicinal , ring (chemistry) , electronegativity , chemical shift , substituent , fluorine , methyl group , carbon fibers , hydrogen bond , stereochemistry , crystallography , molecule , organic chemistry , group (periodic table) , materials science , composite number , composite material
Carbon‐13 and hydrogen NMR data are presented for several cyclopropanes with one to four fluorine atoms attached to the ring. Substituents directly attached to a ring carbon are found to unshield that carbon to an extent increasing with their electronegativity, but remote substituents may have an opposite effect. Relative orientation of the substituent groups, especially if they are bulky, also has a strong influence on the ring‐carbon shifts. Chemical shifts of carbons in methyl groups attached to the ring change to an extent which is additive in the effects of gem and cis substituents. One‐bond coupling of ring carbons with fluorines is affected both by geminal and vicinal substituents, in a way generally related to their electronegativity. It is tentatively concluded that two‐bond coupling between ring carbons and ring‐attached fluorines depends in magnitude primarily on what groups are cis to the fluorine. Two‐bond coupling between a carbon atom in a ring‐attached methyl and the hydrogen gem to the methyl appears to be vanishingly small, but there is appreciable three‐bond coupling of the methyl carbons to vicinal hydrogens. Copyright © 2008 John Wiley & Sons, Ltd.