The infrared spectra and structure of o-sulfobenzimide (saccharin) and of its nitranion: An ab initio force field treatment

The structure of o-sulfobenzimide (saccharin) and of its nitranion has been studied on the basis of both infrared spectra and ab initio force field calculations. A good agreement has been found between the theoretical and experimental spectroscopic characteristics of the particles studied. The theoretical method used gives a good description of the strong spectral changes caused by the conversion of the saccharin molecule into the corresponding nitranion. The structural changes which accompany this conversion are essential and they spread over the whole sulfocarboximide group and the adjacent bonds. The nitranionic charge is delocalized over the phenylene group (0.29 e(-)), sulfonyl group (0.26 e(-)), nitranionic center (0.25 e(-)), and carbonyl group (0.20 e(-)).