Origin of deuterium isotope effects on carbon-13 chemical shifts

Journal Article · Wed Apr 30 04:00:00 EDT 1986 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00269a015· OSTI ID:5658385

Servis, K L; Domenick, R L

In an attempt to model deuterium isotope effects on carbon-13 chemical shifts in the NMR spectra of aliphatic molecules and carbocations, ab initio calculations have been performed at the STO-3G level. The total charge and the gross orbital charges on the nuclei in these compounds were calculated as a function of the C-H bond lengths. The gross atomic charge and the gross orbital charges vary linearly with the bond length for small displacements around the equilibrium bond length. Assuming a charge shift relationship and reasonable values of the isotope effect on bond displacement, the magnitude and directions of the variations of electron density with C-H bond length were found to be sufficiently large to account for the magnitude and sign of the chemical shift isotope effects in acetone and the 2-propyl cation. The sign of ..beta..-deuterium isotope effects in cations with two-electron three-center bonds is not adequately accounted for.

• Research Organization: Univ. of Southern California, Los Angeles
• OSTI ID: 5658385
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:9; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
ALKANES
BOND LENGTHS
CALCULATION METHODS
CARBON
CARBON 13
CARBON ISOTOPES
CATIONS
CHARGE DENSITY
CHARGE DISTRIBUTION
CHARGED PARTICLES
CHEMICAL SHIFT
DATA
DEUTERIUM
DIMENSIONS
ELEMENTS
EVEN-ODD NUCLEI
HYDROCARBONS
HYDROGEN
HYDROGEN ISOTOPES
INFORMATION
IONS
ISOTOPE EFFECTS
ISOTOPES
LENGTH
LIGHT NUCLEI
MAGNETIC RESONANCE
NMR SPECTRA
NONMETALS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
RESONANCE
SPECTRA
STABLE ISOTOPES
THEORETICAL DATA