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Deuterium Isotope Effects on 13C Chemical Shifts in cis-Stilbene

✍ Scribed by Z. Meić; P. Novak; D. Vikić-Topić; V. Smrećki

Publisher
John Wiley and Sons
Year
1996
Tongue
English
Weight
574 KB
Volume
34
Category
Article
ISSN
0749-1581

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✦ Synopsis

Over 100 isotope effects on "C chemical shifts were determined in a series of deuteriated cis-stilbene isotopomers. The magnitude and sign of these effects depend on the position and the number of deuterium atoms in the molecule.

The variations in two-and three-bond effects were rationalized by steric interactions between the phenyl ring and the olefinic group. The six-bond effects in cis-stilbene isotopomers are related to the molecular Ph-C= C dihedral angle, as in other binuclear aromatic molecules. In [para-'HJ-cis-stiIbene the isotope effect over ten bonds was observed, amounting to 2.0 ppb. In mono-and didenterio-cis-stilbenes, effects over up to three bonds from the site of the deuteriation have a positive sign and decrease monotonously in magnitude. In contrast, effects through more than three bonds generally show an alternation in sign and oscillations in magnitude. In polydeuteriated cis- stilbenes, changes in sign and magnitude are governed by the additivity rule, which reproduces the observed values of isotope effects within a few percent.

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