Rotational Spectrum of Saccharin: Structure and Sweetness.

We present the first high-resolution rotational study of the artificial sweetener saccharin. By combining laser ablation (LA), narrow- and broadband Fourier transform microwave techniques (FTMW), and supersonic expansions, we have transferred the solid of saccharin (mp 229 °C) to a supersonic jet and captured its rotational spectrum. The rotational constants were accurately determined by fitting more than 60 rotational transitions for the parent and 34S isotopic species in the 6.4-10.4 GHz frequency range. Experiment and complementary quantum-chemical calculations provide accurate geometrical parameters for saccharin, the first artificial sweetener investigated by high-resolution microwave spectroscopy. The detailed structural information extracted from the rotational and 14N nuclear quadrupole coupling constants provided useful data in the context of the old theories of sweetness.