Snail poison, metaldehyde

Ethanal (acetaldehyde) polymerizes under the influence of acids to the cyclic trimer, paraldehyde, and a cyclic tetramer, metaldehyde. Paraldehyde has been used as a relatively nontoxic sleep-producing drug (hypnotic). Metaldehyde is used as a poison for snails and slugs, Snarol. Ketones do not appear to form stable polymers like those of aldehydes. 

Acetaldehyde boils near room temperature, and it can be handled as a liquid. Acetaldehyde is also used as a trimer (paraldehyde) and a tetramer (metaldehyde), formed from acetaldehyde under acid catalysis. Heating either of these compounds provides dry acetaldehyde. Paraldehyde is used in medicines as a sedative, and metaldehyde is used as a bait and poison for snails and slugs. 

Metaldehyde is widely used in the United States as a snail and slug poison. In Europe, it is also used as a solid fuel for small heaters. The pellets are often mistaken for cereal or candy. Common commercial products containing metaldehyde (2-4%) include Cory s Slug and Snail Death, Deadline for Slugs and Snails, and Bug-Geta Snail and Slug Pellets. 

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