Chloral

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Chloral
Chloral
Chloral
Names
Preferred IUPAC name
Trichloroacetaldehyde
Other names
Trichloroethanal
Identifiers
  • 75-87-6 ☑Y
3D model (JSmol)
  • Interactive image
ChemSpider
  • 6167 ☑Y
ECHA InfoCard 100.000.829
EC Number 200-911-5
KEGG
  • C14866 ☑Y
PubChem CID
  • 6407
UNII
  • FLI06WS32H ☑Y
Properties
C2HCl3O
Molar mass 147.38 g·mol−1
Appearance Colorless, mobile, oily liquid
Odor Pungent and irritating
Density 1.404 g/cm3
Melting point −57.5 °C (−71.5 °F; 215.7 K)
Boiling point 97.8 °C (208.0 °F; 370.9 K)
Forms soluble hydrate
Solubility in ethanol Miscible
Solubility in diethyl ether Miscible
Solubility in chloroform Miscible
Acidity (pKa) 9.66
−6.77×10−5 cm3/mol
1.45572
Hazards
Lethal dose or concentration (LD, LC):
LD50 (median dose)
480 mg/kg (rat, oral)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
‹See TfM›☒N verify (what is ☑Y‹See TfM›☒N ?)
Infobox references

Chloral, also known as trichloroacetaldehyde or trichloroethanal, is the organic compound with the formula Cl3CCHO. This aldehyde is a colourless oily liquid that is soluble in a wide range of solvents. It reacts with water to form chloral hydrate, a once widely used sedative and hypnotic substance.

Production

Chloral is produced commercially by the chlorination of acetaldehyde in the presence of hydrochloric acid, producing chloral hydrate. Ethanol can also be used as a feedstock. This reaction is catalyzed by antimony trichloride:

H3CCHO + 3 Cl2 + H2O → Cl3CCH(OH)2 + 3 HCl

The chloral hydrate is distilled from the reaction mixture. The distillate is then dehydrated with concentrated sulfuric acid, after which the heavier acid layer (containing the water) is drawn off:

Cl3CCH(OH)2 → Cl3CCHO + H2O

The resulting product is purified by fractional distillation.[1] Small amounts of chloral hydrate occur in some chlorinated water.

Key reactions

Chloral tends to form adducts with water (to give chloral hydrate) and alcohols.

Aside from its tendency to hydrate, chloral is notable as a building block in the synthesis of DDT. For this purpose, chloral is treated with chlorobenzene in the presence of a catalytic amount of sulfuric acid:

Cl3CCHO + 2 C6H5Cl → Cl3CCH(C6H4Cl)2 + H2O

This reaction was described by Othmar Zeidler in 1874.[2] The related herbicide methoxychlor is also produced from chloral.

Treating chloral with sodium hydroxide gives chloroform Cl3CH and sodium formate HCOONa

Cl3CCHO + NaOH → Cl3CH + HCOONa

Chloral is easily reduced to trichloroethanol, which is produced in the body from chloral.[1]

Safety

Chloral and chloral hydrate have the same properties biologically since the former hydrates rapidly. Chloral hydrate was routinely administered to patients on the gram scale with no lasting effects. Prolonged exposure to the vapors is unhealthy however, with a LC50 for 4-hour exposure of 440 mg/m3.[1]

See also

References

  1. ^ a b c Jira, Reinhard; Kopp, Erwin; McKusick, Blaine C.; Röderer, Gerhard; Bosch, Axel; Fleischmann, Gerald, "Chloroacetaldehydes", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a06_527.pub2
  2. ^ Zeidler, Othmar (1874). "Verbindungen von Chloral mit Brom- und Chlorbenzol" [Compounds of chloral with bromo- and chlorobenzene]. Berichte der deutschen chemischen Gesellschaft. 7 (2): 1180–1181. doi:10.1002/cber.18740070278.
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