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Long-range intrinsic NMR isotope shifts as a probe of hyperconjugation: demonstration of the angular dependence in bicyclic carbocations

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00337a001· OSTI ID:5994736
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The long-range NMR isotope shift is demonstrated to be strongly angle dependent in the manner expected for a hyperconjugative origin in two benzylic cations with rigid bicyclic alkyl systems. The NMR isotope shifts produced at /sup 19/F due to deuterium substitution in the 2-(p-fluorophenyl)-2-bicyclo(2.2.2)octyl cation are 0.143 ppm for each deuterium at C/sub 3/ and 0 ppm for deuterium at the bridgehead C/sub 1/ position. In the 2-(p-fluorophenyl)-2-bicyclo(2.2.1)heptyl cation, the isotope shifts at/sup 19/F are 0.202 ppm for exo substitution at C/sub 3/ and 0 ppm for endo substitution. These results are consistent with other experimental and theoretical data, indicating that an exo-C-H is better aligned for hyperconjugation than an endo-C-H in classical norbornyl cations. 34 references.

Research Organization:
Northeastern Univ., Boston, MA
OSTI ID:
5994736
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 106:25; ISSN JACSA
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ALKENES
AROMATICS
CATIONS
CHARGED PARTICLES
COMPARATIVE EVALUATIONS
CYCLOALKENES
DATA
DEUTERIUM
DEUTERIUM COMPOUNDS
ELEMENTS
EXPERIMENTAL DATA
FLUORINATED AROMATIC HYDROCARBONS
FLUORINE
HALOGENATED AROMATIC HYDROCARBONS
HALOGENS
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
INFORMATION
IONS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
NMR SPECTRA
NONMETALS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
SPECTRA
SPECTRAL SHIFT
STABLE ISOTOPES
STRUCTURAL CHEMICAL ANALYSIS
TRACER TECHNIQUES