Chemical Shift Correlation NMR Research Articles

Correlation of NMR chemical shifts of 2‐methyl protons of substituted benzazoles with hammett's substituents constants

AbstractThe chemical shifts of 2‐methyl protons of twenty one 5‐ and 6‐ substituted benzazoles determined in carbon tetrachloride solution, were plotted against the Hammett substituent constants using δm for groups in the 5‐ position and δp for groups in the 6‐ position, obtaining satisfactory linear correlations. These results are taken to indicate that electronic effects are transmitted to the 2‐position predominantly through the nitrogen atom and that virtually no transmission occurs through the hetero atom. The deshielding effect of the hetero atom is opposite to the electronegativity and this may be qualitatively explained in terms of different aromaticity of these heterocycles.