Chloral

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Chloral
Chloral Chloral-2D-skeletal.png
Chloral
Chloral Chloral-3D-vdW.png
Chloral
Names
Preferred IUPAC name
Trichloroacetaldehyde
Other names
Trichloroethanal
Identifiers
3D model (JSmol)
506422
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.829 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 200-911-5
KEGG
PubChem CID
UNII
  • InChI=1S/C2HCl3O/c3-2(4,5)1-6/h1H
    Key: HFFLGKNGCAIQMO-UHFFFAOYSA-N
  • ClC(Cl)(Cl)C=O
Properties
C2HCl3O
Molar mass 147.38 g·mol−1
AppearanceColorless 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
9.48846
Hazards
GHS labelling:
GHS-pictogram-skull.svg GHS-pictogram-exclam.svg
Danger
H301, H302, H315, H319, H335
P261, P264, P270, P271, P280, P301+P310, P301+P312, P302+P352, P304+P340, P305+P351+P338, P312, P321, P330, P332+P313, P337+P313, P362, P403+P233, P405, P501
Lethal dose or concentration (LD, LC):
480 mg/kg (rat, oral)
Related compounds
Related compounds
Trifluoroacetaldehyde, Bromal, Iodal
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Chloral, also known as trichloroacetaldehyde or trichloroethanal, is the organic compound with the formula Cl3CCHO. This aldehyde is a colourless 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. [1]

Contents

Production

Chloral was first prepared, and named, by the German chemist Justus von Liebig in 1832. [2] Liebig treated anhydrous ethanol with dry chlorine gas. [3]

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. [4] 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. [5] 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. [4]

Toxicity

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 toxic with a LC50 for 4-hour exposure of 440 mg/m3. [4]

See also

Related Research Articles

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Ethanol is an organic compound with the chemical formula CH3CH2OH. It is an alcohol, with its formula also written as C2H5OH, C2H6O or EtOH, where Et stands for ethyl. Ethanol is a volatile, flammable, colorless liquid with a characteristic wine-like odor and pungent taste. It is a psychoactive recreational drug, and the active ingredient in alcoholic drinks.

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<span class="mw-page-title-main">Dichloromethane</span> Chemical compound

Dichloromethane is an organochlorine compound with the formula CH2Cl2. This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with water, it is slightly polar, and miscible with many organic solvents.

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<span class="mw-page-title-main">Ethanethiol</span> Chemical compound

Ethanethiol, commonly known as ethyl mercaptan, is an organosulfur compound with the formula CH3CH2SH. is a colorless liquid with a distinct odor. Abbreviated EtSH, it consists of an ethyl group (Et), CH3CH2, attached to a thiol group, SH. Its structure parallels that of ethanol, but with sulfur in place of oxygen. The odor of EtSH is infamous. Ethanethiol is more volatile than ethanol due to a diminished ability to engage in hydrogen bonding. Ethanethiol is toxic in high concentrations. It occurs naturally as a minor component of petroleum, and may be added to otherwise odorless gaseous products such as liquefied petroleum gas (LPG) to help warn of gas leaks. At these concentrations, ethanethiol is not harmful.

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References

  1. Luknitskii, F. I. (1975). "Chemistry of Chloral". Chemical Reviews. 75 (3): 259–289. doi:10.1021/cr60295a001.
  2. See:
    • Liebig, Justus (1832). "Ueber die Verbindungen, welche durch die Einwirkung des Chlors auf Alkohol, Aether, ölbildendes Gas und Essiggeist entstehen" [On the compounds which arise by the reaction of chlorine with alcohol [ethanol], ether [diethyl ether], oil-forming gas [ethylene], and spirit of vinegar [acetone]]. Annalen der Pharmacie (in German). 1 (2): 182–230. doi:10.1002/jlac.18320010203. pp. 189–191 "Wirkung des Chlors auf Alkohol" [Reaction of Chlorine with alcohol [i.e., ethanol]] ; pp. 191–194 "Darstellung des Chloral[s]" [Preparation of chloral] ; pp. 195–198 "Eigenschaften des Chlorals" [Properties of chloral].
      Liebig named chloral on p. 191. From p. 191: "Ich werde in dem Folgenden zeigen, dass bei einer vollkommnen Zersetzung des Alkohols das Chlor den Wasserstoff desselben abscheidet und diesen Wasserstoff ersetzt; es entsteht eine neue eigenthümliche Verbindung von Chlor, Kohlenstoff und Sauerstoff, welche ich, indem ich keinen zweckmässigeren Namen weiss, vorläufig Chloral nenne. Dieser Name ist dem Worte Aethal nachgebildet." (In the following, I will show that during a complete breakdown of ethanol, chlorine removes its [i.e., ethanol's] hydrogen and replaces this hydrogen; there arises a strange new compound of chlorine, carbon, and oxygen, which I — as I know no more appropriate name — provisionally name "chloral". This name is patterned after the word Aethal [i.e., ethyl].)
    • Reprinted in: Liebig, Justus (1832). "Ueber die Verbindungen, welche durch die Einwirkung des Chlors auf Alkohol, Aether, ölbildendes Gas und Essiggeist entstehen" [On the compounds which arise by the reaction of chlorine with alcohol [ethanol], ether [diethyl ether], oil-forming gas [ethylene], and spirit of vinegar [acetone]]. Annalen der Physik und Chemie. 2nd series (in German). 24 (2): 243–295. Bibcode:1832AnP...100..243L. doi:10.1002/andp.18321000206. pp. 250-252 "Wirkung des Chlors auf Alkohol" [Reaction of Chlorine with alcohol [i.e., ethanol]] ; pp. 252–255 "Darstellung des Chloral[s]" [Preparation of chloral] ; pp. 255–259 "Eigenschaften des Chlorals" [Properties of chloral].
    • Gmelin, Leopold, ed. (1848). Handbuch der Chemie (in German). Vol. 4 (4th ed.). Heidelberg, [Germany]: Karl Winter. pp. 893–897.
  3. Liebig passed dry chlorine gas through anhydrous ethanol for 11–13 days, until hydrogen chloride ceased to form. The product was dried by shaking with concentrated sulfuric acid, decanted over chalk, and then distilled. (Liebig, 1832), pp. 191–194.
  4. 1 2 3 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.
  5. 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.