¹⁷O NMR spectroscopy: Intramolecular hydrogen bonding in hydroxypyridine carboxy esters

Abstract

Natural abundance 17O nmr chemical shift data for 8 aryl esters and 10 pyridine carboxy esters, including 6 ortho‐hydroxy esters, recorded in acetomitrile at 75° are reported. The carbonyl group 17O nmr chemical shift data for methyl 2‐, 3‐ and 4‐pyridinecarboxylate are correlated with σ+ constants. The hydrogen bonding component (ΔδHB) to the ester carbonyl 17O nmr chemical shift for the intramolecular hydrogen bonded ortho‐hydroxy systems are 9.8 ppm, 13.6 ppm and 4.3 ppm for benzoates, 2‐pyridinecarboxylates and 4‐pyridinecarboxylates, respectively. The relationships of the ester ΔδHB values to other hydrogen bond acceptor ΔδHB values are discussed.

Hydrogen-Bonding in Cyclic 2-(3-Oxo-3-phenylpropyl)-Substituted 1,3-Diketones: 17O-NMR Spectra and X-Ray Structure Determination

“…Intramolecular H-bonding in a molecule generally causes shielding of the O-atom [2 ± 10]. Shielding of the O-atom by intramolecular H-bonding (Dd HB value) ranging from À 5 to À 50 ppm has been reported for various compounds including enaminones [3] [4], ketones [5], aldehydes [6], amides [7], and esters [8].…”