Paraldehyde

• 2,4,6 -trimethyl-1 ,3,5- trioxane
• Paracetaldehyde

N05CC05

Colorless liquid with a sweet odor

Sedative, hypnotic

0.99 g · cm -3 ( 20 ° C)

12 ° C

124 ° C.

10 hPa ( 20 ° C)

• Slightly soluble in water: 120 g · l-1 (20 ° C)
• Miscible with ethanol, chloroform, ether,

1.405 at 20 ° C.

Attention

2711 mg · kg -1 ( LD50, rat, oral)

Template: Infobox chemical / molecular formula search available

Paraldehyde is a chemical compound. It is the trimer of acetaldehyde. Is a cyclic acetal. Accordingly, the molecule is unstable, even to diluted acids.

Production and representation

Paraldehyde is formed by cyclization of three molecules of acetaldehyde in the presence of sulfuric acid. The product formation is dependent on temperature of the cyclization reaction. At room temperature the formation of the trimer is preferable. At lower temperatures around -10 ° C rather the tetramer metaldehyde arises.

Properties

Paraldehyde is a clear and colorless liquid that is soluble with typical organic solvents miscible in water as well. The solubility in water decreases while the temperature increases.

For the molecular structure theoretically four stereoisomers can be formulated. In fact there are only the two structures (1) and (2), known as cis -and trans- paraldehyde. The structures (3) and (4) are unlikely for steric reasons, since the methyl groups would interfere with each other here.

Safety

The mounting is difficult because of the instability. It puts to an antioxidant and stored away from light and heat or in amber glass bottles. The fractured quantities should be kept as small as possible and quickly consumed.

Proof

• The aldehyde reacts in the Tollensprobe with a Silberdiamminkomplex and forms a silver mirror of elemental silver.
• In the Iodoformreaktion the CH3 - CO group can be detected.

For both reactions, an acid hydrolysis of the Paraldehyds to acetaldehyde is required.

Paraldehyde is monographed in pharmacopoeias.