| Chloracetophenone was originally synthesized by the German chemist, Graebe, in 1869 (other sources indicate 1871). CN tear agent—a so-called lacrymator due to its irritating effects on the eyes— was developed as a chemical weapon during World War I by British and probably American chemists as well. The pure compound itself is a crystalline solid, but is dissolved in a solvent or used in thermal grenades for delivery. Although it was not produced in time to see actual combat, it apparently was used by Japanese forces as early as 1930 during the pacification campaigns against Taiwanese aboriginals. CN is a potent harassing or riot control agent (RCA) that is the active ingredient in Mace™, this moniker apparently derived from its chemical formula name “Methylchloroform chloroacetophenone.” Because of its relatively toxic profile, CN has largely been displaced by the tear agent CS, the latter being more effective and now standardized worldwide as the RCA of choice. It is unclear what role, if any, CN agent would play in terms of military or terrorist threats.
The irritating effects of CN are especially intense in the eyes, as well as being painful to exposed skin surfaces. With exposure to high doses of CN, rashes and even blistering can occur, some of the more sensitive areas for exposure being under the arms and in the groin. It is possible for lethal concentrations of CN agent to develop in enclosed areas, and thus this non-lethal agent in the open field may become quite deadly, depending upon the method of dispersal. For CN to create noticeable effects, a field concentration of about 10mg-min/m3 is required. When delivered in a solvent (liquid form), the median lethal concentration (Lct50) for CN is estimated at 7 grams-min/m3, and if vaporized in a thermal delivery system, it is about twice this figure. |
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