1H, 13C, 15N NMR and theoretical study of protonated carbamic acids and related compounds

Mono-O-protonated carbamic acid, mono-O-protonated N-methyl carbamate, and mono-O-protonated methyl carbamate and di-O-protonated N,N-bis(carboxyl)-1,2-diaminoethane were prepared in FSO3H/SO2ClF and FSO3H:SbF5/SO2ClF at -78 degrees C and were characterized by H-1, C-13, and N-15 NMR spectroscopy. Persistent diprotonated carbamic acid, diprotonated N-methyl carbamate, and diprotonated methyl carbamate were not observed under these conditions. The structures, energies, and C-13 and N-15 NMR chemical shifts of mono-, and diprotonated carbamic acids as well as other protonated species were also calculated by ab initio/IGLO/GIAO-MP2 method and compared with the experimental results.