2-Chloroacetophenone

2-Chloroacetophenone (phenacyl chloride, CN) was first synthesized by Graebe in 1871 and recognized as a powerful lachrymator (tear-inducing agent) by Staudinger and Rugheimer in 1912. [1] During World War I, it was evaluated as a potential chemical warfare agent (France used it in combination with other agents), though it was not as effective as mustard gas in military applications. After WWI, CN found a second life as a riot control and crowd dispersal agent for law enforcement — often as a 1% solution in a liquid carrier in grenades and aerosol devices. In the 1960s it became the active ingredient in personal defense sprays marketed as 'Mace.' Law enforcement agencies worldwide used CN-based tear gas for decades, and it remains in use today, though it has been substantially displaced by OC (oleoresin capsicum, pepper spray) and CS gas (2-chlorobenzalmalononitrile) because CN has a narrower safety margin. [2] Unlike OC and CS, CN is an alkylating agent — it can covalently react with proteins and DNA, which makes it more toxic at high doses and raises concerns about carcinogenicity and genotoxicity. It causes intense lacrimation, pain, and temporary incapacitation at low concentrations. At higher concentrations or doses (particularly in enclosed spaces), CN can cause pulmonary edema, deep chemical burns, and has been associated with fatalities. [3] CN is listed as a HAP and as an alkylating agent with carcinogenic potential.

Law enforcement officers, military personnel, and security forces using CN for crowd control are occupationally exposed through inhalation during deployment. Bystanders and protesters at tear-gassed scenes experience involuntary inhalation and eye/skin exposure. Individuals using CN-based personal defense sprays (original Mace) have skin and aerosol exposure risks. Manufacturing workers producing CN have significant occupational exposures.

CN is qualitatively different from OC pepper spray in its toxicological mechanism — it is an alkylating agent that can form covalent bonds with cellular molecules, raising concerns about mutagenicity and potential carcinogenicity not relevant to OC. [2] In enclosed spaces or at high doses, CN can cause pulmonary edema (fluid accumulation in the lungs), which can be life-threatening. Multiple fatalities have been documented, primarily in situations where subjects were confined in tear-gassed spaces. Eye damage including corneal scarring occurs with direct contact. Skin burns can occur with concentrated formulations or prolonged contact.

Law enforcement officers who regularly deploy CN grenades or sprays, military personnel trained with CN, and manufacturers of CN products have occupational exposure. Civilians in areas where tear gas is deployed — including protesters and bystanders — face involuntary exposures that may be significant in enclosed or downwind settings.

1. Modern personal defense sprays using OC (pepper spray) are safer than CN-based Mace — switch if using an older CN product. 2. Law enforcement agencies should transition from CN to CS or OC for crowd control, which have wider safety margins. 3. If exposed to tear gas: move to fresh air immediately, remove contaminated clothing, flush eyes with large amounts of clean water for at least 15 minutes, and shower with soap and water. 4. Individuals with pre-existing respiratory conditions (asthma, COPD) should seek medical evaluation after any significant tear gas exposure. 5. CN should never be deployed in enclosed spaces.