Deuterium isotope effects on the carbon-13 chemical shifts of carbocations

Journal Article · Wed Nov 19 04:00:00 EST 1980 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00544a010· OSTI ID:6584182

Servis, K L; Shue, F F

The study of ..beta..-deuterium isotope effects on the carbon-13 chemical shifts of carbocations provides an unambiguous tool for probing the mechanism of charge delocalization in carbocations and a new criterion for differentiating carbocations with different charge-localization mechanisms. ..beta..-Deuterium isotope shifts on the cationic carbon centers are positive (downfield shift) for classical static carbonium ions, zero for classical delocalized ions, and negative (upfield shift) for nonclassical sigma- or ..pi..-bridged nonclassical ions. For classical carbocations, the ..beta.. effect is related to the demand for hyperconjugative stabilization by the alkyl group. For sigma- or ..pi..-bridged nonclassical ions in general, the ..beta.. effect arises from changes in the relative importance of the contributing resonance structure upon deuterium substitution. The observation of a remote ..gamma.. or delta effect can provide further information as to the nature of the bridging.

• Research Organization: Univ. of Southern California, Los Angeles
• OSTI ID: 6584182
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 102:24; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
CARBON 13
CARBON COMPOUNDS
CARBON ISOTOPES
CATIONS
CHARGED PARTICLES
CHEMICAL SHIFT
DATA
DEUTERIUM
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
HYDROGEN ISOTOPES
INFORMATION
IONS
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
STABLE ISOTOPES