Examples are bis(2-chloroethyl)ether, the (2-haloethyl)amines (nitrogen mustards), and sulfur sesquimustard, which has two ??-chloroethyl thioether groups (ClH2C-CH2-S-) connected by an ethylene (-CH2CH2-) group.[citation needed] These compounds have a similar ability to alkylate DNA, but their physical properties, e.g. melting point, vary.