2-chloroacetophenone

Chloroacetophenone is thermally stable, and is the only tear agent that is distillable at ambient conditions.

Chloroacetophenone was first synthesized by Carl Graebe in 1871 by passing chlorine into boiling acetophenone. Phenacyl chloride is readily available and was first prepared by chlorination of acetophenone vapour. It may also be synthesized by the Friedel-Crafts acylation of benzene using chloroacetyl chloride, with an aluminium chloride catalyst:

The Japanese made use of CN to suppress an indigenous rebellion in Taiwan in 1930. During the Second Sino-Japanese War, the Imperial Japanese Army used another irritating substance, diphenylchlorarsine against the Chinese instead. Because of CN's significantly greater toxicity, CN has largely been supplanted for military use by CS gas. Even though CN is still supplied to paramilitary and police forces in a small pressurized aerosol known as “Mace” or tear gas, CN's use is falling because pepper spray both works and disperses more quickly than CN and is less toxic than CN. The term "Mace" came into being because it was the brand-name invented by one of the first American manufacturers of CN aerosol sprays. Subsequently, in the United States, Mace became synonymous with tear-gas sprays in the same way that Kleenex has become strongly associated with facial tissues (a phenomenon known as a genericized trademark). Like CS gas, this compound irritates the mucous membranes (oral, nasal, conjunctival and tracheobronchial). Sometimes it can give rise to more generalized reactions such as syncope, temporary loss of balance and orientation. More rarely, cutaneous irritating outbreaks have been observed and allergic contact permanent dermatitis. At high concentrations, CN may cause corneal epithelial damage and chemosis. It has also accounted for at least five deaths, which have resulted from pulmonary injury and/or asphyxia. TRPA1 (Transient Receptor Potential-Ankyrin 1) ion channel expressed on nociceptors (especially trigeminal) has been implicated as the site of action for CN, in vivo and in vitro.

Known uses of phenacyl chloride include the following compounds: Bazinaprine, Myfadol, Phenactropinium