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Deuterium isotope effects on 13C and 15N nuclear shielding in o-hydroxyazo dyes

✍ Scribed by Antonín Lyčka; Poul Erik Hansen

Publisher
John Wiley and Sons
Year
1984
Tongue
English
Weight
336 KB
Volume
22
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

Deuterium isotope effects on the ^13^C and ^15^N nuclear shieldings of o‐hydroxyazo compounds are described. Both the direct and the equilibrium contributions were determined. Large direct deuterium isotope effects on ^15^N nuclear shieldings for ^1^Δ, ^2^Δ and ^4^Δ and negative Δ^1^J(^15^NH) [D] values were observed. Isotope effects on ^15^N nuclear shieldings, because of their magnitudes, are shown to be very useful in determining changes in the azo–hydrazone equilibrium. Isotope effects on ^13^C nuclear shieldings are smaller, but the effects observed at the carbon resonances of the N‐phenyl ring are likewise very useful in determining the shift in the equilibrium. Deuterium substitution leads in all cases to a shift in the equilibrium so that the content of the predominant form of the protio compound is increased.

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