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Deuterium isotope effects on 13 C and 15 N nuclear shielding in o ‐hydroxyazo dyes
Author(s) -
Lyčka Antonín,
Hansen Poul Erik
Publication year - 1984
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270220910
Subject(s) - deuterium , kinetic isotope effect , isotope , chemistry , carbon 13 , nuclear reaction , radiochemistry , analytical chemistry (journal) , atomic physics , nuclear physics , physics , organic chemistry
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.