H-1, C-13, N-15 NMR AND AB-INITIO IGLO GIAO-MP2 STUDY OF MONOPROTONATED, DIPROTONATED, TRIPROTONATED, AND TETRAPROTONATED GUANIDINE

Mono- and diprotonated guanidines were prepared in superacid solutions and studied by H-1, C-13, and N-15 NMR spectroscopy. The structures, energies, and NMR chemical shifts were also calculated by ab initio/IG LO/GIAO-MP2 method. Excellent agreement were found between experimenta l and calculated C-13 and N-15 NMR chemical shifts. No persistent trip rotonated guanidine was observed. Tri- and tetraprotonated guanidines were also studied by ab initio/IGLO/GIAO-MP2 method.