Editing CS gas (section)

== Production ==
CS is [[Chemical synthesis|synthesized]] by the reaction of [[2-Chlorobenzaldehyde|2-chlorobenzaldehyde]] and [[malononitrile]] via the [[Knoevenagel condensation]]:
[[File:CS-Gas-Synthese.svg|422x422px|thumb|Preparation of CS|left]]
::ClC<sub>6</sub>H<sub>4</sub>CHO + [[Malononitrile|H<sub>2</sub>C(CN)<sub>2</sub>]] → ClC<sub>6</sub>H<sub>4</sub>CHC(CN)<sub>2</sub> + H<sub>2</sub>O

The reaction is catalysed with a weak base like [[piperidine]] or [[pyridine]]. The production method has not changed since the substance was discovered by Corson and Stoughton.<ref name="corson">{{cite journal|vauthors= Corson BB, Stoughton RW| title=Reactions of Alpha, Betha-Unsaturated Dinitriles|journal=J Am Chem Soc|year= 1928|volume=50|pages=2825–2837|doi=10.1021/ja01397a037|issue= 10}}</ref> Other bases, solvent free methods and [[microwave]] promotion have been suggested to improve the production of the substance.<ref>{{cite journal|vauthors= Pande A, Ganesan K, Jain AK, Gupta PK, Malhotr RC| title=Novel Eco-Friendly Process for the Synthesis of 2-Chlorobenzylidenemalononitrile and ITS Analogues Using Water As a Solvent|journal=Org Proc Res Develop|year= 2005|volume=9|pages=133–136| doi=10.1021/op0498262|issue= 2}}</ref>

The physiological properties had been discovered already by the chemists first synthesising the compound in 1928:
"Physiological Properties. Certain of these dinitriles have the effect of sneeze and tear gases. They are harmless when wet but to handle the dry powder is disastrous."<ref name="corson" />

=== Use as an aerosol ===

As 2-chlorobenzalmalononitrile is a solid at room temperature, not a [[gas]], a variety of techniques have been used to make this solid usable as an [[aerosol]]:

* Melted and sprayed in the molten form.
* Dissolved in organic solvent.
* CS2 dry powder (CS2 is a [[silicon]]ized, micro-pulverized form of CS).
* CS from thermal grenades by generation of hot gases.<ref name=UweHeinrich />

In the [[Waco Siege]] in the United States, CS was dissolved in the organic solvent [[dichloromethane]] (also known as methylene chloride). The solution was dispersed as an [[aerosol]] via explosive force and when the highly volatile dichloromethane evaporated, CS crystals precipitated and formed a fine dispersion in the air.<ref name=UweHeinrich />