Sulfur mustards:
2-Chloroethylchloromethylsulfide
Mustard gas: (Bis(2-chloroethyl)sulfide
1
So in original. Probably should not be preceded by an open parenthesis.
Bis(2-chloroethylthio)methane
Sesquimustard: 1,2-Bis(2-chloroethylthio)ethane
1,3-Bis(2-chloroethylthio)-n-propane
1,4-Bis(2-chloroethylthio)-n-butane
1,5-Bis(2-chloroethylthio)-n-pentane
Bis(2-chloroethylthiomethyl)ether
O-Mustard: Bis(2-chloroethylthioethyl)ether.