Structure of nitroguanidine: Nitroamine or nitroimine? New NMR evidence from 15N‐labeled sample and 15N spin coupling constants

The structure of nitroguanidine was investigated by the application of 15N, 1H and 13C NMR spectroscopy of a fully 15N‐labeled sample in DMSO‐d6 and DMF solutions and by 15N CP/MAS NMR in the solid state. These spectra confirm the nitroimine structure which has been suggested by other investigations in recent years, and do not lend any support to the commonly used nitroamine structure or for a tautomeric equilibrium with the nitroamine. Useful 15N spin coupling constants to the 1H and 13C nuclei in the assigned structure are reported.