Metaldehyde

• 2,4,6,8- tetramethyl-1 ,3,5,7 - tetroxocane
• Metacetaldehyd

Colorless, tasteless, highly flammable solid with a weak characteristic odor

Fixed

1.27 g · cm -3

45.5 ° C

0.3 hPa ( 20 ° C)

• Very poor in water ( 190 mg · l-1 at 22 ° C)
• Slightly soluble in ether and ethanol
• Soluble in benzene and chloroform >

Risk

227-690 mg · kg -1 ( LD50, rat, oral)

Template: Infobox chemical / molecular formula search available

Metaldehyde is a cyclic ether. It is the cyclic tetramer of acetaldehyde. The trimer is called paraldehyde. Under the name of metaldehyde also polymeric acetaldehyde ( CH3CHO ) n is distributed. It is used as a solid fuel and a molluscicide, but must not be used in the manufacture or treatment of cosmetic products, according to German Cosmetics Ordinance. Metaldehyde is contained for example in slug pellets.

Production and representation

Metaldehyde is formed by cyclization of four molecules of acetaldehyde in the presence of sulfuric acid at low temperature. The product formation is dependent on temperature of the cyclization reaction. At room temperature the formation of the trimer, paraldehyde is preferred. At lower temperatures around -10 ° C rather the tetramer metaldehyde arises.

Properties

Metaldehyde is a colorless, tasteless, highly flammable solid with a weak characteristic odor, a melting point at 45.5 ° C. The values ​​given in the literature melting and sublimation temperatures between 100 ° C and 250 ° C refer to polymeric acetaldehyde and result rather from depolymerization.

As paraldehyde more stereoisomers may also be formulated for the molecular structure of metaldehyde. The methylene groups may each be axially or equatorially on the ring.