Journal of the chemical society-perkin transactions 2 issue:4 pages:831-834
The H-1 and C-13 NMR spectra of the complex between 1,8-bis(dimethylamino)naphthalene and 3,5-dichlorophenol have been studied at temperatures between 30 degrees C and -70 degrees C in CD2Cl2 and at different acid to base concentration ratios. At a temperature of -60 degrees C a splitting of the H-1 and C-13 signals of DMAN and DMANH(+) is observed. The protonation degree deduced from the NMR data and the intensity of the Bohlmann bands are in very good agreement. At a temperature below 8 degrees C, a splitting (2.6 Hz) of the methyl protons caused by spin-spin coupling with the (NHN)(+) bridge protons is observed. Comparison with literature data and with the coupling constant determined in this work for protonated N,N-dimethylaniline suggest that the potential surface of the NHN+ cation includes two symmetrically situated wells between which fast proton migration takes place.