Solvent effects on the NMR shieldings of nitrogen atoms in azole and azine systems: their counterparts in the gas phase

Abstract

The ¹⁴N shieldings of 14 pyrrole and 39 pyridine nitrogens belonging to azoles, oxazoles, thiazoles, azines and indolizines measured in 13 different solvents in the same laboratory by Witanowski et al. are examined in the light of the solvent polarity/polarizability (SPP), solvent acidity (SA) and solvent basicity (SB) pure solvent scales. The results are explained in terms of the structural properties of the compounds. Based on the analysis of the solvent effect, the corresponding ¹⁴N shieldings in the gas phase for the 53 nitrogens studied are obtained, the experimental determination of which is a major challenge.