phenols were prepared and investigated by 1H and 13C NMR spectroscopy in chloroform-d1 solution. The chemical shifts of intramolecular hydrogen-bonded protons in Mannich bases depend on the pKa of the parent phenols. A correlation between Hammett's constants, σp, and 13C NMR chemical shifts of para carbon atoms has been found. All the results obtained from 1H and 13C NMR spectra show that in the case