Chloropicrin

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Chloropicrin
Chloropicrin.png Chloropicrin-3D-balls.png
Identifiers
CAS number 76-06-2 YesY
ChemSpider 13861343 YesY
UNII I4JTX7Z7U2 YesY
KEGG C18445 YesY
ChEBI CHEBI:39285 YesY
Jmol-3D images Image 1
Properties
Molecular formula CCl3NO2
Molar mass 164.375
Appearance colorless liquid
Density 1.692 g/ml[1]
Melting point -69 °C
Boiling point 112 °C (dec)
Hazards
GHS pictograms The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
EU classification Very Toxic T+
R-phrases R22, R26, R36/37/38, R43, R50/53
S-phrases S36/37, S38, S45
Main hazards Extremely toxic and irritating to skin, eyes, and lungs.
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 4: Very short exposure could cause death or major residual injury. E.g., VX gas Reactivity code 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g., fluorine Special hazards (white): no codeNFPA 704 four-colored diamond
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Chloropicrin, also known as PS, is a chemical compound currently used as a broad-spectrum antimicrobial, fungicide, herbicide, insecticide, and nematicide.[2] Its chemical structural formula is Cl3CNO2.

Discovery[edit]

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 + 11 NaOCl → 3 Cl3CNO2 + 3 Na2CO3 + 3 NaOH + 2 NaCl

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

Properties[edit]

Chloropicrin’s chemical formula is CCl3NO2 and its molecular weight is 164.38 grams/mole.[3] Pure chloropicrin is a colorless liquid, with a boiling point of 112 °C.[3] Chloropicrin is highly soluble in water with solubility of 2,000 milligrams per liter at 25 °C.[3] It is volatile, with a vapor pressure of 23.2 millimeters of mercury (mm Hg) at 25 °C; the corresponding Henry’s Law Constant is 0.00251 atmosphere-cubic meter per mole.[3] The octanol-water partition coefficient (Kow) of chloropicrin is estimated to be 269.[3] Its soil adsorption coefficient (Koc; normalized to soil organic matter content) is 25 cm3/g.[3]

Use[edit]

In agriculture, chloropicrin is injected into soil prior to planting a crop in order to clean the soil of a broad spectrum of fungi, microbes, insects, and other harmful pests.[4][5] It is commonly used as a stand alone treatment or in combination / co-formulation with methyl bromide and 1,3-Dichloropropene.[5][6]

Safety[edit]

At the national level, chloropicrin is regulated by the United States Environmental Protection Agency as a restricted use pesticide.[4][7] The EPA has approved chloropicrin as safe for use by farmers nationwide. The distribution and use of chloropicrin is available only to licensed professionals and specially certified growers who are trained in its proper and safe use.[4][7] In the US, occupational exposure limits have been set at 0.1 ppm over an eight-hour time-weighted average.[8]

Agriculture[edit]

In 2008 the US EPA re-approved chloropicrin as safe for use in agricultural settings, stating that treatments "can provide benefits to both food consumers and growers. For consumers, it means more fresh fruits and vegetables can be cheaply produced domestically year-round because several severe pest problems can be efficiently controlled."[9][10][11] To ensure chloropicrin is used safely, the EPA requires a strict set of protections for handlers, workers, and persons living and working in and around farmland during treatments.[4][10] EPA protections were increased in both 2011 and 2012, reducing fumigant exposures and significantly improving safety.[12] Protections include the training of certified applicators supervising pesticide application, the use of buffer zones, posting before and during pesticide application, fumigant management plans, and compliance assistance and assurance measures.[11][13][14]

High Concentrations[edit]

Unlike its use in agriculture, in unregulated settings chloropicrin can be harmful to humans. Chloropicrin can be absorbed systemically through inhalation, ingestion, and the skin. At high concentrations it is severely irritating to the lungs, eyes, and skin.[15] In World War I German forces used concentrated chloropicrin against Allied forces as a tear gas. While not as lethal as other chemical weapons, it caused vomiting and forced Allied soldiers to remove their masks to vomit, exposing them to other, more toxic chemical gases used as weapons during the war.[6]

Preparation[edit]

Chloropicrin is manufactured by the reaction of nitromethane with sodium hypochlorite:[16]

H3CNO2 + 3 NaOCl → Cl3CNO2 + 3 NaOH

References[edit]

  1. ^ http://msds.chem.ox.ac.uk/CH/chloropicrin.html
  2. ^ "RED Fact Sheet: Chloropicrin". US Environmental Protection Agency. 10 July 2008. p. 2. Retrieved 20 September 2013. 
  3. ^ a b c d e f "Executive Summary - Evaluation of Chloropicrin As A Toxic Air Contaminant" (PDF). Department of Pesticide Regulation - California Environmental Protection Agency. February 2010. p. iv. Retrieved 20 September 2013. 
  4. ^ a b c d "Chloropicrin - Background". Retrieved 20 September 2013. 
  5. ^ a b http://www.workcover.nsw.gov.au/Documents/Publications/AlertsGuidesHazards/DangerousGoodsExplosivesFireworksPyrotechnics/chloropicrin_fact_sheet_1371.pdf[dead link]
  6. ^ a b Amos Alfred Fries; Clarence Jay West (1921). Chemical warfare. McGraw-Hill book company, inc. p. 144. 
  7. ^ a b "Chloropicrin Mitigation Proposal" (PDF). Department of Pesticide Regulation - California Environmental Protection Agency. 15 May 2013. p. 1. Retrieved 20 September 2013. 
  8. ^ "NIOSH Pocket Guide to Chemical Hazards". Centers for Disease Control and Prevention. Retrieved 7 November 2013. 
  9. ^ "Amended Reregistration Eligibility Decision (RED) for Chloropicrin" (PDF). United States Environmental Protection Agency. May 2009. Retrieved 20 September 2013. 
  10. ^ a b "Chloropicrin Mitigation Proposal" (PDF). Department of Pesticide Regulation - California Environmental Protection Agency. 15 May 2013. p. 2. Retrieved 20 September 2013. 
  11. ^ a b "Environmental Protection Agency (EPA) Re-Registers Chloropicrin As Safe For Use Nationwide". Retrieved 22 October 2013. 
  12. ^ "Chloropicrin Mitigation Proposal" (PDF). Department of Pesticide Regulation - California Environmental Protection Agency. 15 May 2013. p. 2. Retrieved 20 September 2013. "The Amended RED incorporated final new safety measures to increase protections for agricultural workers and bystanders. These measures establish a baseline for safe use of the soil fumigants throughout the United States, reducing fumigant exposures and significantly improving safety." 
  13. ^ "Chloropicrin Mitigation Proposal" (PDF). Department of Pesticide Regulation - California Environmental Protection Agency. 15 May 2013. p. 2. Retrieved 20 September 2013. "The new measures appearing on soil fumigant Phase 2 labels include buffer zones and posting, emergency preparedness and response measures, training for certified applicators supervising applications, Fumigant Management Plans, and notice to State Lead Agencies who wish to be informed of applications in their states." 
  14. ^ "Chloropicrin - Frequently Asked Questions". Retrieved 21 October 2013. 
  15. ^ Chloropicrin (PS): Lung Damaging Agent. National Institute for Occupational Safety and Health. Emergency Response Safety and Health Database, August 22, 2008. Retrieved December 23, 2008.
  16. ^ Sheldon B. Markofsky "Nitro Compounds, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.