Paraldehyde

Paraldehyde is the cyclic trimer of acetaldehyde molecules. Formally, it is a derivative of 1,3,5-trioxane, with a methyl group substituted for a hydrogen atom at each carbon. The corresponding tetramer is metaldehyde. A colourless liquid, it is sparingly soluble in water and highly soluble in ethanol. Paraldehyde slowly oxidizes in air, turning brown and producing an odour of acetic acid. It attacks most plastics and rubbers and should be kept in glass bottles.

Not to be confused with Paraformaldehyde.
Paraldehyde
Names
IUPAC name
2,4,6-Trimethyl-1,3,5-trioxane
Systematic IUPAC name
2,4,6-Trimethyl-1,3,5-trioxane
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.004.219
EC Number
  • 204-639-8
KEGG
MeSH Paraldehyde
UNII
  • InChI=1S/C6H12O3/c1-4-7-5(2)9-6(3)8-4/h4-6H,1-3H3 Y
    Key: SQYNKIJPMDEDEG-UHFFFAOYSA-N Y
  • InChI=1/C6H12O3/c1-4-7-5(2)9-6(3)8-4/h4-6H,1-3H3
    Key: SQYNKIJPMDEDEG-UHFFFAOYAO
  • CC1OC(C)OC(C)O1
Properties
C6H12O3
Molar mass 132.159 g·mol−1
Appearance Colourless liquid
Odor Sweet
Density 0.996 g/cm3
Melting point 12 °C (54 °F; 285 K)
Boiling point 124 °C (255 °F; 397 K)
soluble 10% vv at 25 Deg.
Vapor pressure 13 hPa at 20 °C
-86.2·10−6 cm3/mol
Pharmacology
N05CC05 (WHO)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Flammable
GHS labelling:
Warning
H226
P210, P233, P303+P361+P353, P370+P378, P403+P235, P501
Flash point 24°C - closed cup
Explosive limits Upper limit: 17 %(V)
Lower limit: 1.3 %(V)
Lethal dose or concentration (LD, LC):
Oral - Rat - 1,530 mg/kg
Dermal - Rabbit - 14,015 mg/kg
Safety data sheet (SDS)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Paraldehyde was first observed in 1835 by the German chemist Justus Liebig; its empirical formula was determined in 1838 by Liebig's student Hermann Fehling. The German chemist Valentin Hermann Weidenbusch (1821–1893), another of Liebig's students, synthesized paraldehyde in 1848 by treating acetaldehyde with acid (either sulfuric or nitric acid) and cooling to 0°C. He found it quite remarkable that when paraldehyde was heated with a trace of the same acid, the reaction went the other way, recreating acetaldehyde.

Paraldehyde has uses in industry and medicine.

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