chloropicrin

Chloropicrin
IUPAC name	trichloro(nitro)methane
Other names	PS
Identifiers
CAS number	76-06-2 Y
SMILES	ClC(Cl)(Cl)[N+]([O-])=O
InChI	1/CCl3NO2/c2-1(3,4)5(6)7
InChI key	LFHISGNCFUNFFM-UHFFFAOYAJ
ChemSpider ID	13861343
Properties
Molecular formula	CCl3NO2
Molar mass	164.375
Appearance	colorless liquid
Melting point	-69 °C
Boiling point	112 °C (dec)
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Chloropicrin, also known as "PS", is a chemical compound with the structural formula Cl₃CNO₂. This colourless highly toxic liquid was once used in chemical warfare and is currently used as a fumigant and nematocide.^[1][2]

History

Chloropicrin was first discovered in 1848 by a Scottish chemist John Stenhouse. He prepared it by the reaction of a chlorinating agent with picric acid:

HOC₆H₂(NO₂)₃ + 10 NaOCl → 3 Cl₃CNO₂ + 3 NaOH + NaCl + 3 CO₂

Because of the precursor he used, Stenhouse named the compound chloropicrin, although the two compounds are structurally dissimilar.

Arguably, chloropicrin's most famous use was in World War I. In 1917, there were reports that the Germans were testing and using a new chemical in warfare.^[3] That chemical was chloropicrin. While not as lethal as other chemical weapons, it caused vomiting and was a lachrymatory agent.^[3] This combination of properties forced Allied soldiers to remove their masks to vomit, exposing them to toxic gases.^[3] This caused a large number of casualties on the Italian front.^[3]

Preparation

Chloropicrin is manufactured by the reaction of nitromethane with sodium hypochlorite:^[4]

H₃CNO₂ + 3 NaOCl → Cl₃CNO₂ + 3 NaOH

Properties

As listed in the Table, chloropicrin is a colorless liquid that is insoluble in water, with which it is stable. With a vapor pressure of 24 mm Hg, its volatility is between that of phosgene and mustard gas in persistency, although closer to phosgene because it is related to the compound.^[5] Tests have shown that chloropicrin causes humans to shut their eyes involuntary.^[3] Chloropicrin can be absorbed systemically through inhalation, ingestion, and the skin. It is severely irritating to the lungs, eyes, and skin.^[6] Because of these properties, chloropicrin can only be delivered in shell form as a chemical weapon.^[5]

Application

Chloropicrin, today, is used as a fumigant to control pests found in the soil.^[1] Although less common it can be used as a poison for vertebrates, such as rabbits.^[1] Chloropicrin is commonly used in combination with other fumigants, such as methyl bromide, for increased potency and as a warning agent.^[1]

Chloropicrin has been used in chemical warfare. It first appeared in 1917 when the Germans tested a new chemical weapon on the Italian front.^[5] The new chemical weapon was devastating to the Allies at first, since they had never encountered it before.

Safety

Chloropicrin is a highly toxic chemical: NIOSH 1995 states that:

-Chloropicrin is a lacrimator and a severe irritant of the respiratory system in humans; it also causes severe skin irritation on contact. When splashed onto the eye chloropicrin has caused corneal oedema and liquification of the cornea.

-Exposure to concerntrations of 15ppm cannot be tolerated for more than 1 minute, and exposure to 4ppm for a few seconds is temporaily disabling.

-Exposure to 0.3-0.37 ppm chloropicrin for 3 to 30 seconds causes tearing and eye pain. Exposure to 15ppm for a few seconds can cause respiratory tract injury.

-Exposure to 119ppm in air for 30 minutes is lethal; death is caused by pulmonary oedema.

Examples of industrial exposure in humans: 27 workers in a cellulose factory who were exposed to high levels of chloropicrin for 3 minutes developed pneumonitis after 3 to 12 hours of irritated coughing and difficulty on breathing; they subsequently devloped pulmonary oedema and one died.

EU classification of chloropicrin is: R22 Harmful if swallowed, R26 Very toxic by inhalation, R36/37/38 Irritating to eyes, skin and respiratory system, R43 May cause sensitisation by skin contact, R50/53 Very toxic to aquatic organisms, may cause long term adverse effects in the aquatic environment.

Because of chloropicrin's stability, protection requires highly effective absorbents, such as activated charcoal.^[3] Chloropicrin, unlike its relative compound phosgene, is absorbed readily at any temperature, which may pose a threat in low or high temperature climates.^[5]

The use of the substance has been restricted by the US government, although such restriction is outdated now ^[7]

See also

• Use of poison gas in World War I.

References