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Metam sodium

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Metam sodium is an organosulfur compound with the formula CH3NHCS2Na. The compound is a sodium salt of a dithiocarbamate. The compound exists as a colorless dihydrate, but most commonly it is encountered as an aqueous solution.[2] It is used as a soil fumigant, pesticide, herbicide, and fungicide. It is one of the most widely used pesticides in the United States, with approximately 60 million pounds used in 2001.[3]

Metam-sodium belongs to two HRAC groups, so it is designated Group A/C (Aus), Group A/C1 (global) and Group 1/5 (numeric).[4]

Preparation and properties

Metam sodium is prepared by combining methylamine, carbon disulfide, and sodium hydroxide:[2]

CH3NH2 + CS2 + NaOH → CH3NHCS2Na + H2O

It also arises from the reaction of methyl isothiocyanate and sodium thiolate.[1]

Upon exposure to the environment, metam sodium decomposes to methyl isothiocyanate and other sulfur compounds.[5]

Safety and environmental considerations

Metam sodium is nonpersistent in the environment since it decomposes rather quickly to toxic methyl isothiocyanate and carbon disulfide.[5] In 1991 a tank car with 19,000 gallons of a metam sodium based pesticide spilled into Sacramento River above Lake Shasta. This killed all fish in a 41-mile stretch of the river. 20 years later the rainbow trout population had recovered.[6]

See also

References

  1. 12Merck Index, 11th Edition, 5860.
  2. 12Hartwig, Jürgen; Sommer, Herbert; Müller, Franz (2008). "Nematicides". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a17_125.pub2. ISBN 978-3527306732.
  3. ↑2000-2001 Pesticide Market EstimatesArchived 2009-02-07 at the Wayback Machine, U.S. Environmental Protection Agency
  4. ↑Hertfordshire, University of. "Metam-sodium (Ref: N 869)". sitem.herts.ac.uk.
  5. 12Bretaudeau Deguigne M, Lagarce L, Boels D, Harry P (2011). "Metam sodium intoxication: the specific role of degradation products--methyl isothiocyanate and carbon disulphide--as a function of exposure". Clin Toxicol (Phila). 49 (5): 416–22. doi:10.3109/15563650.2011.585472. PMID 21740140. Archived from the original on May 23, 2024.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ↑"Largest chemical spill in California history". dtsc.ca.gov. Retrieved 2017-12-11.
  • Metam sodium in the Pesticide Properties DataBase (PPDB)