Well to start with, there are lots of "chemicals" used in antiseptic soaps and soaps in general if it comes to that.
If your after the name of a chemical with antiseptic properties used in soaps, there are quite a few. These include Triclosan (Irgasan DP300), Carbolic Acid (Phenol) and Chlorhexhidine and Tea Tree Oil. There are others as well though.
The most common antiseptic chemical in soap is Triclosan.