<unk>  is a substituted acetophenone. It is a useful building block in organic chemistry. Apart from that, it has been historically used as a riot control agent, where it is designated CN.
Phenacyl chloride
Pyritinol
Didecyldimethylammonium chloride
Tosylchloramide
Undecylenic acid
Gedocarnil
Tienilic acid
Ferruginol