Dependence of Carbon Chemical Shifts in the 13C NMR Spectra of 5-Hydroxy-1,4-naphthoquinon-4-imines on Position of Tautomeric Equilibrium

In the 13 C NMR spectra of 5-hydroxy-1,4-naphthoquinon-4-imines the para -quinonimine form is characterized by the presence of signals from C 5 in the region 160-162 ppm and from C 10 at ∼115 ppm whereas typical signals of the ana-quinoid form are those of C 5 in the region 169-170 ppm and C 10 at 110-11 ppm.