Oops. Close, but not quite. (Following structures are from http://class.fst.ohio-state.edu/FST...res/lect14.html)

This molecule is sucrose. Notice the OH on the left-most carbon, the CH2OH sticking up from the left side of the second ring, and the CH2OH on the right.




This is sucralose. Noticee that there are now Cl (chlorine) atoms replacing the -OH (hydroxyl) groups in those three locations.




Everything else is the same. Only those three OH groups have been replaced with Cl. Now in the body the enzyme sucrase breaks down sucrose into glucose and fructose which are absorbed into the blood. And as you may be aware, enzymes work with a "lock and key" mechanism. The substrate (sucrose) must fit exactly into the binding site on the enzyme molecule (sucrase). Except that in sucralose, the Cl atoms are differently shaped than the OH groups. So sucralose doesn't fit into the sucrase like it should. So it's not metabolized like sucrose.

However, other enzymes will attack it, but not very efficiently, so only a portion of what is ingested will be broken down and metabolized by the body. (About 20% of it I think.)

So, sucralose, being 600 times sweeter than sugar, and not being broken down in the body like sugar, makes an excellent replacement.

However..... proponents of sucralose say that the chlorine atom is already in our body (it is, but not the atom, but an ion of chlorine - from the NaCl and other salts we consume). But on the sucralose molecule it isn't in the ion form. It is covalently bonded to the atom, the same way chlorine and fluorine atoms are bonded to things like freon and other organic compounds. The long-term effect this will have on the body is yet to be seen. So the 100% safety of this substance has not yet been shown.

Chemistry lesson over. Any questions?

Joan