DFT and experimental study on the IR spectra and structure of acesulfame sweetener

The high-intensity non-nutritive sweetener 6-methyl-1,2,3-oxathiazin-4(3K)-on-2,2-dioxide (Acesulfame-potassium, Additive E-950) and its neutral molecule have been studied by both quantum chemical calculations and infrared spectra. Density functional theory has been exploited to calculate structural parameters and relative stability of lactim and lactam tautomers of acesulfame in different environment. Theoretical results agree very well with the experimental findings and suggested that the lactam tautomer may be the most stable form in the gas phase and nonpolar solvents, while in polar DMSO one the lactim form dominates. The detailed IR spectra of both tautomers of acesulfame molecule and acesulfame anion were reported. In addition, the changes in both spectra and structures (steric and electronic), caused by the conversion of molecule into corresponding anion are discussed.

► The acesulfame exists as lactam tautomer in the gaseous phase, nonpolar and weakly polar solvent.
► The lactim form is more stable in DMSO solution.
► The conversion of the molecule into anion causes essential changes in the structure of sulfocarboximide group.
► The new azanionic center bears 50% of the whole anionic net charge.