Quantum chemical calculations of the molecular structure of diphenylguanidine and experimental studies of its tautomerism in solution

MNDO-PM3 and AM1 quantum chemical calculations of the molecular structure o f N,N'-diphenylguanidine (DPG) prove that the molecule preferably exists as an asymmetric tautomer with a basic center C=N-. IR and UV spectral data, dipole moments, and average molecular weights of DPG solutions in nonpolar and low-polar solvents confirm the results of calculations, indicating form ation of hydrogen-bonded cyclic self-associates of DPG in solution.