The active ingredient in Splenda, sucralose, is closely related to sucrose. In a five-step synthesis, three positions on the sugar are chlorinated, which renders it both indigestible and intensely sweet.
Like, 600 times sweeter than sugar.
So, if you got a sugar-sized packet of pure
sucralose, your iced tea would taste like rock candy. So, Splenda actually contains mostly flavorless maltodextrin.
But how do we separate the sucralose from the maltodextrin?
Well, the chlorine atoms make sucralose much more hydrophobic
(oil-liking) than an ordinary sugar like maltodextrin. So, by using a nonpolar solvent like acetone or isopropanol the sucralose can be dissolved and the maltodextrin filtered off.
For you organic chemistry fans out there, I've included the synthesis below.