Carbon-13 n.m.r. investigation on the nitrogen methylation of the mono- and diazanaphthalenes

The 13C n.m.r. spectra of the N-methylated mono- and diazanaphthalenes have been recorded and analysed. It has been shown that N-methylation as well as N-protonation in cinnoline occur predominantly at the -nitrogen atom. N-methylation and N-protonation show a similar effect on the 13C chemical shift

13C n.m.r. investigation on the first and second nitrogen protonation in the diazanaphthalenes

The 13C chemical shifts of the diazanaphthalenes have been recorded as a function of the pH value, providing classical titration curves. From these curves the pK1 and pK2 values have been determined taking into account the activity coefficients. The changes in 13C chemical shift under the influence of nitrogen protonation (Δδ) can be described by two protonation parameter sets