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17O NMR spectroscopy of 4-substituted pyridine N-oxides: Substituent and solvent effects

✍ Scribed by D. W. Boykin; A. L. Baumstark; P. Balakrishnan

Publisher: John Wiley and Sons
Year: 1985
Tongue: English
Weight: 309 KB
Volume: 23
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1260230414

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✦ Synopsis

Abstract

The ^17^O chemical shifts for 4‐substituted pyridine N‐oxides at natural abundance were measured in acetonitrile at 50°C. Electron withdrawing groups caused deshielding and electron donating groups caused shielding of the ^17^O resonance. The data are correlated with ^17^O chemical shifts of substituted anisoles by DSP treatment and with ionization potentials. The chemical shift range for the substituents (methoxy to nitro) is exceptionally large (102 ppm). The ^17^O signal of the pyridine N‐oxides is substantially shifted in aqueous solution; the differences in chemical shifts between acetonitrile and water for the nitro, parent and methoxy compounds are 85, 75 and 59 ppm, respectively.

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