Distinction between the tautomeric forms of sulfanilamide derivatives by 13C-NMR.

The application of 13C-NMR for the distinction between amido and imido tautomers of sulfanilamide derivatives in DMSO solution is described. The differentiation is based on delta delta, the change in chemical shift of a sulfanilamide from the neutral form (in DMSO solution) to the anion (in aqueous alkaline solution). The delta delta values of three C atoms (C1, C1', C4) are suitable for the differentiation between the tautomers. The conclusions confirm previous results.