mustards

Also contains definition of: nitrogen mustards
https://doi.org/10.1351/goldbook.M04071
Compounds having two β-haloalkyl groups bound to a sulfur atom, as in (XC2H2C2H2)2S, and their analogues, the nitrogen (and phosphorus) mustards, (XC2H2C2H2)2NR. Compounds having one β-haloalkyl group and one β-hydroxyalkyl group on S are termed hemi- or semi-mustards by some chemists.
Source:
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1350 [Terms] [Paper]