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Deuterium Isotope Effects on 13C NMR Chemical Shifts Reflect the Smaller Steric Size of CD3 Compared to CH3 Groups§

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posted on 2000-11-15, 00:00 authored by Kerstin Ibrom, Gunther Kohn (, Kai-Uwe Boeckmann, Roswitha Kraft, Petra Holba-Schulz, Ludger Ernst
A CD3 group close in space to (but many bonds distant from) a carbon atom A causes a substituent effect on the chemical shift of CA that is algebraically smaller than the effect of a CH3 group, in agreement with the notion of shorter C−D relative to C−H bonds. Hence, the deuterium isotope effect of CD3 upon δ(CA) is shielding when the substituent effect is deshielding, and vice versa.

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