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August 05, 2008

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hko

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 ?

Arvin

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

Hi,
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

erhard

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