Metaldehyde

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Metaldehyde
Skeletal formula
Ball-and-stick model
IUPAC name

r-2, c-4, c-6, c-8-tetramethyl-
1,3,5,7-tetroxocane

Other names

2,4,6,8-tetramethyl-1,3,5,7-
tetraoxocanemetacetaldehyde

Identifiers
CAS number 108-62-3 YesY
PubChem 61021
ChemSpider 54981 N
KEGG C18744 N
Jmol-3D images Image 1
Properties
Molecular formula C8H16O4
Molar mass 176.212 g/mol
Density 1.27 g/cm³
Melting point 246 °C
Boiling point sublimes at 110-120 °C
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Metaldehyde is an organic compound with the formula (CH3CHO)4. It is commonly used as a pesticide against slugs, snails, and other gastropods. It is the cyclic tetramer of acetaldehyde.[1]

Production and properties

Metaldehyde is obtained in moderate yields by treatment of acetaldehyde with various acid catalysts, such as hydrogen bromide. The reaction is reversible, upon heating to about 80 °C, metaldehyde reverts to acetaldehyde. Metaldehyde exists as a mixture of stereoisomers, molecules that differ with respect to the relative orientation of the methyl groups on the 8-membered ring.

Granules of metaldehyde (trade name Limacide)

Uses

As a pesticide

It is sold under various trade names as a molluscicide, including Antimilice, Ariotox, Blitzem (in Australia), Cekumeta, Deadline, Defender (in Australia), Halizan, Limatox, Limeol, Meta, Metason, Mifaslug, Namekil, Slug Fest Colloidel 25, and Slugit. Typically it is applied in the form of slug pellets, which normally include a wheat bait. Metaldehyde acts on the pest by contact or ingestion, and the aqueous environment inside the pest's cells readily hydrolyzes metaldehyde into acetaldehyde, the molecule associated with an alcohol hangover.

Other uses

Metaldehyde is also used as a camping fuel. It may be purchased in a tablet form to be used in small stoves, and for preheating of Primus type stoves. It is sold under the trade name of "META" by Lonza Group of Switzerland.

Safety

Metaldehyde has a toxicity profile identical to that for acetaldehyde, being mildly toxic[2] and a respiratory irritant at the 50 ppm level.

Metaldehyde-containing slug baits should be used with caution as they are toxic to dogs and cats.[3] If ingested by dogs or cats tremors, drooling, and restlessness will proceed to seizures and death within hours to days if treatment is not started quickly. Due to this toxicity, pet owners may want to investigate non pet toxic alternatives.[4] The tablets resemble sweetmeats and do not taste bad, making accidental ingestion possible by children or even by adults unaware of their true nature. Their use was popular during the inter-war period and several cases of poisoning resulted.[5] Baits may contain a bittering agent to prevent accidental consumption by pets or children.

In popular culture

In chapter 5 of Missee Lee from Arthur Ransome's Swallows and Amazons series, Susan of the Swallows is shown using meta fuel to preheat a Primus stove. The substance is branded "Meta Fuel" but its properties as described in the book - a jelly-like substance which melts when lit and burns with a blue flame leaving no residue - are more suggestive of gelled alcohol in tablet form; genuine metaldehyde fuel tablets are brittle, sublime rather than melting, burn with a yellow flame and leave a powdery residue.[6]

References

  1. ↑ Marc Eckert, Gerald Fleischmann, Reinhard Jira, Hermann M. Bolt, Klaus Golka "Acetaldehyde" in Ullmann's Encyclopedia of Industrial Chemistry, 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a01_031.pub2.
  2. ↑ Toxicology of metaldehyde
  3. ↑ "Pests in Gardens and Landscapes". University of California, Davis. Retrieved 2010-08-03. 
  4. ↑ "Slugging Out Spring". Dr. Heidi Houchen, DVM. 
  5. ↑ Miller, Reginald (December 1928). "Poisoning by "Meta Fuel" Tablets (Metacetaldehyde)". Archive of Diseases in Childhood. 3(18): 292–295. Retrieved 2013-08-04. 
  6. ↑ "Meta Fuel - Classic Camp Stoves". Retrieved 2013-08-04. 

External links

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