Tautomerism in 1‐hydroxy‐2‐naphthaldehyde Schiff bases: Calculation of tautomeric isomers using carbon‐13 NMR

Article type: Research Article

Authors: Salman, Salman R. | Kamounah, Fadhil S.^;

Affiliations: Department of Chemistry, College of Science, University of Qatar, P.O. Box 2713, Doha, Qatar | Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK‐2100 Copenhagen, Denmark

Note: [] Corresponding author. Tel.: +45 35 32 18 23; Fax: +45 39 27 12 07; E‐mail: [email protected].

Abstract: Tautomeric equilibria in intramolecularly hydrogen bonded Schiff bases is studied on the basis of solution 13C NMR chemical shifts. NMR spectroscopic data and comparison with two anils model compound, namely, salicylideneaniline (1A) and naphthalylidinequinoline (2A) were used to represent the enol (A) and the keto (H) forms. The 13C NMR chemical shifts data of the novel series 4A (compounds, 4‐12) were used together with the values 13C chemical shifts data of compounds 1A and 2A to calculate the % keto form. The calculated % keto form of 3A was compared to that calculated for series 4A compounds.

Keywords: Carbon‐13 chemical shift, keto–enol equilibrium, UV‐Vis spectroscopy, 1‐hydroxy‐2‐naphthaldehyde Schiff bases, percentage of the keto form

Journal: Spectroscopy, vol. 17, no. 4, pp. 747-752, 2003