1 H, 13 C, 15 N NMR and Theoretical Study of Protonated Carbamic Acids and Related Compounds 1

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 FSO 3 H/SO 2 ClF and FSO 3 H:SbF 5 /SO 2 ClF at −78 °C and were characterized by 1 H, 13 C, and 15 N NMR spectroscopy. Persistent diprotonated carbamic acid, diprotonated N -methyl carbamate, and diprotonated methyl carbamate were not observed under these conditions. The structures, energies, and 13 C and 15 N 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.