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August 05, 2008


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I assume that carbon shifts also should allow a clear distinction between the two tautomers, since beta-carbons in the enamin part are normally found at higer field (ca. 5ppm ?). Are there carbon shift reported ?


Hello Heinz,

I agree that these two tautomers can be differentiated by 13C chemical shifts. However, neither reference (Left structure: J.Heterocycl. Chem., 2002, v.39, p.131.) report any 13C NMR data.

In cases where the unknown contains multiple nitrogen atoms, many elucidators will collect 15N NMR data to assist in the elucidation process.

Erhard T.K. Haupt

I just read this contibution (and the older one) and was surprised about the discussion and comments. There are three papers dealing with this topic using 1H, 13C and 15N-NMR:

Solution Structures of Pyrophthalones, III
Complementary Application of 14N/15 N-NMR Spectroscopy to Study Solution Structures of Pyrophthalones
Authors: E.T.K. Haupt, M. Eggers
Published in: Spectr. Lett., 31(3), 521 (1998)

Haupt, Erhard T. K.; Tom Dieck, Heindirk; Bonchev, P. Solution structures of pyrophthalones. II. Structure and conformation of iminopyrophthalone - a high-resolution proton, carbon-13, nitrogen-15 and solid state 13C-CP/MAS-NMR study. Zeitschrift fuer Naturforschung, B: Chemical Sciences (1987), 42(11), 1419-23

Haupt, Erhard T. K.; Tom Dieck, Heindirk; Bonchev, P. Solution structures of pyrophthalones, I. Structure and conformation of 1,3-indandionato-2(2-pyridinium)betaine - a proton/carbon-13 NMR approach. Zeitschrift fuer Naturforschung, B: Chemical Sciences (1987), 42(1), 31-6

Maybe this is of help....

Bets regards


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