Protonation Studies of Schiff Bases Using 13C and 15N-NMR Spectroscopy

Almudena Perona; Dionisia Sanz; Rosa Claramunt; Elena Pinilla; M. Torres; José Elguero

doi:10.3390/ecsoc-10-01403

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Synthesis of 1-vinyl isoquinolines and isoindolines by cyclization of acyliminium ions derived from allenamides

Protonation Studies of Schiff Bases Using 13C and 15N-NMR Spectroscopy

Almudena Perona

^{*

1},

Dionisia Sanz

¹,

Rosa M. Claramunt

¹,

Elena Pinilla

²,

M. Rosario Torres

²,

José Elguero

¹ Dpto. de Química Orgánica y Bio-Orgánica, Fac. de Ciencias, UNED, 28040 Madrid, Spain
² Dpto. de Química Inorgánica, Fac. de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain
³ Instituto de Química Médica, CSIC, Juan de la Cierva 3, 28006 Madrid, Spain

Published: 30 November 2006 by MDPI in The 10th International Electronic Conference on Synthetic Organic Chemistry session General Organic Synthesis

https://doi.org/10.3390/ecsoc-10-01403

Abstract: ¹³C and ¹⁵N-NMR spectroscopy provides clear evidence that the Schiff bases of 3-hydroxy-4-pyridinecarboxaldehyde exist as a mixture of hydroxyimino and oxoenamino tautomers in acid media. The study of the stabilities of the tautomeric forms has been approached using density functional calculations (B3LYP/6-31G**). The X-ray molecular structure of (E)-4-[(4-bromophenylimino)methyl]-3- hydroxypyridinium tetrafluoroborate has been solved.

Keywords: Schiff bases, Tautomerism, Hydrogen bonds, NMR spectroscopy, Density functional calculations, X-ray

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Almudena Perona

Dionisia Sanz

Rosa Claramunt

Elena Pinilla

M. Torres

José Elguero