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Chloral hydrate chemical structure
Chloral hydrate

IUPAC chemical name
CAS number
ATC code
Chemical formula C2HCl3O · H2O
Molecular weight 165.5gmol-1
Bioavailability ?
Metabolism ?
Elimination half-life ?
Excretion ?
Pregnancy category ?
Legal status Schedule IV
Routes of administration Oral capsule/syrup, Rectal suppository
Template:Chembox OtherNamesTemplate:Chembox InChITemplate:Chembox AppearanceTemplate:Chembox DensityTemplate:Chembox BoilingPtTemplate:Chembox BioavailTemplate:Chembox AdminRoutesTemplate:Chembox MetabolismTemplate:Chembox HalfLifeTemplate:Chembox ExcretionTemplate:Chembox Legal statusTemplate:Chembox PregCatTemplate:Chembox ExternalMSDSTemplate:Chembox EUClassTemplate:Chembox RPhrasesTemplate:Chembox Other
style="background: #F8EABA; text-align: center;" colspan="2" Chloral hydrate
CAS number 302-17-0
PubChem 2707
Molecular formula C2H3Cl3O2
Molar mass 165.403 g/mol
Melting point

57 °C, 330 K, 135 °F

style="background: #F8EABA; text-align: center;" colspan="2" Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Chloral hydrate is a sedative and hypnotic drug as well as a chemical reagent and precursor. The name chloral hydrate indicates that it is formed from chloral (trichloroacetaldehyde) by the addition of one molecule of water. Its chemical formula is C2H3Cl3O2.

It was discovered through the chlorination of ethanol in 1832 by Justus von Liebig in Gießen.[1][2] The sedative properties where first published in 1869 and subsequently because of its easy synthesis it had a wide spread use.[3] It was widely abused and misprescribed in the late 19th century. Chloral hydrate is soluble in both water and alcohol, readily forming concentrated solutions. A solution of chloral hydrate in alcohol called "knockout drops" was used to prepare a Mickey Finn.

It is, together with chloroform, a minor side-product of the chlorination of water, if organic resudues are present in the water, concentrations rarely exceeding 5 micrograms per litre (µg/l).


Chloral hydrate is produced from chlorine and ethanol in acidic solution. In basic conditions the haloform reaction takes place and chloroform is produced.

4 Cl2 + C2H5OH + H2O → Cl3CCH(OH)2 + 5 HCl



Chloral hydrate is a cheaply available building block chemical. It is the starting material for the production of chloral, which is produced by the distillation of a mixture of chloral hydrate and sulfuric acid, which serves as the desiccant.

Notably, it is used to synthesize isatin. In this synthesis, chloral hydrate reacts with aniline and hydroxylamine to give a condensation product which cyclicizes in sulfuric acid to give the target compound:[4]

File:Synthesis of isatin.png


Chloral hydrate is used for the short-term treatment of insomnia and as a sedative before minor medical or dental treatment. It was largely displaced by the mid-20th century by barbiturates[5] and subsequently by benzodiazepines. It was also formerly used in veterinary medicine as a general anesthetic. Today, it is commonly used as an ingredient in the veterinary anesthetic Equithesin.

In therapeutic doses for insomnia chloral hydrate is effective within sixty minutes, it is metabolized within 4 minutes into trichloroethanol by erythrocytes and plasma esterases and many hours later into trichloroacetic acid. Higher doses can depress respiration and blood pressure. An overdose is marked by confusion, convulsions, nausea and vomiting, severe drowsiness, slow and irregular breathing, cardiac arrhythmia and weakness. It may also cause liver damage and is moderately addictive, as chronic use is known to cause dependency and withdrawal symptoms. The chemical can potentiate various anticoagulants and is weakly mutagenic in vitro and in vivo [How to reference and link to summary or text].

Chloral hydrate is now illegal in the United States without a valid prescription. Chloral hydrate is a schedule IV controlled substance in the United States. Its properties have sometimes led to its use as a date rape drug.

See also


  1. Justus Liebig (1832). Ueber die Zersetzung des Alkohols durch Chlor. Annalen der Pharmacie 1 (1): 31-32.
  2. Justus Liebig (1832). Ueber die Verbindungen, welche durch die Einwirkung des Chlors auf Alkohol, Aether, ölbildendes Gas und Essiggeist entstehen. Annalen der Pharmacie 1 (2): 182-230.
  3. Liebreich, Oskar (1869). Das Chloralhydrat : ein neues Hypnoticum und Anaestheticum und dessen Anwendung in der Medicin ; eine Arzneimittel-Untersuchung, Müller.
  4. Template:OrgSynth
  5. Tariq, Syed H. and Shailaja Pulisetty; “Pharmacotherapy for Insomnia”, Clinics in Geriatric Medicine (24), 2008 p. 93-105 PMID: 18035234
  • Baumgardner, D. J., & Dewsbury, D. A. (1979). Surgical anesthesia of seven rodent species with chloral hydrate: Physiology & Behavior Vol 23(3) Sep 1979, 609-610.
  • Corner, M., Scholte, R., Korf, J., & Mirmiran, M. (1984). Electrocortical activity patterns during chloral hydrate induced sleep in developing rats: Brain Research Bulletin Vol 12(1) Jan 1984, 77-81.
  • Devarajan, S. (1992). Interaction of fluoxetine and chloral hydrate: The Canadian Journal of Psychiatry / La Revue canadienne de psychiatrie Vol 37(8) Oct 1992, 590-591.
  • Dickson, R. A., Williams, R., & Dalby, J. T. (1994). The use of chloral hydrate and sodium amytal during clozapine initiation: The Canadian Journal of Psychiatry / La Revue canadienne de psychiatrie Vol 39(3) Apr 1994, 132-134.
  • Frankland, A., & Robinson, M. J. (2001). Fatal chloral hydrate overdoses: Unnecessary tragedies: The Canadian Journal of Psychiatry / La Revue canadienne de psychiatrie Vol 46(8) Oct 2001, 763-764.
  • Gessner, P. K., & Shakarjian, M. P. (1985). Interactions of paraldehyde with ethanol and chloral hydrate: Journal of Pharmacology and Experimental Therapeutics Vol 235(1) Oct 1985, 32-36.
  • Goldstein, S. E., Birnbom, F., Lancee, W. J., & Darke, A. C. (1978). Comparison of oxazepam, flurazepam and chloral hydrate as hypnotic sedatives in geriatric patients: Journal of the American Geriatrics Society Vol 26(8) Aug 1978, 366-371.
  • Hartmann, E., & Cravens, J. (1973). The effects of long term administration of psychotropic drugs on human sleep: V. The effects of chloral hydrate: Psychopharmacologia Vol 33(3) 1973, 219-232.
  • Hutto, B., Fairchild, A., & Bright, R. (2000). gamma -Hydroxybutyrate withdrawal and chloral hydrate: American Journal of Psychiatry Vol 157(10) Oct 2000, 1706.
  • Kallman, M. J., Kaempf, G. L., & Balster, R. L. (1984). Behavioral toxicity of chloral in mice: An approach to evaluation: Neurobehavioral Toxicology & Teratology Vol 6(2) Mar 1984, 137-146.
  • Krugman, A. D., Ross, S., & Lyerly, S. B. (1964). Drugs and placebos: Effects of instructions upon performance and mood under amphetamine sulphate and chloral hydrate wyith younger subjects: Psychological Reports 15(3) 1964, 925-926.
  • Loewy, J., Hallan, C., Friedman, E., & Martinez, C. (2006). Sleep/Sedation in Children Undergoing EEG Testing: A Comparison of Chloral Hydrate and Music Therapy: American Journal of Electroneurodiagnostic Technology Vol 46(4) Dec 2006, 343-355.
  • Mercer, L. F., & Remley, N. R. (1978). Combined solution of ketamine and chloral hydrate as an anesthetic: Physiology & Behavior Vol 20(4) Apr 1978, 495-496.
  • Napier, T. C., Pirch, J. H., & Peterson, S. L. (1983). Spontaneous unit activity in the globus pallidus following cumulative injections of morphine in phenobarbital- or chloral hydrate-anesthetized rats: Neuropharmacology Vol 22(2) Feb 1983, 165-171.
  • Stone, C. B., & Okun, R. (1978). Chloral hydrate dependence: Report of a case: Clinical Toxicology Vol 12(3) 1978, 377-380.
  • Tabakoff, B., Vugrincic, C., Anderson, R., & Alivisatos, S. G. (1974). Reduction of chloral hydrate to trichlorethanol in brain extracts: Biochemical Pharmacology Vol 23(2) Jan 1974, 455-460.
  • Trulson, M. E., & Trulson, V. M. (1983). Chloral hydrate anesthesia blocks the excitatory response of dorsal raphe neurons to phasic auditory and visual stimuli in cats: Brain Research Vol 265(1) Apr 1983, 129-133.
  • Udall, J. A. (1975). Warfarin interactions with chloral hydrate and glutethimide: Current Therapeutic Research Vol 17(1) Jan 1975, 67-74.

Sedatives edit

(Methaqualone) (Ethchlorvynol) (Chloral Hydrate) (Meprobamate) (Glutethimide) (Methyprylon) (Gamma-hydroxybutyrate) (Gamma-butyrolactone) (Propofol)

Barbiturates edit

{Amobarbital) {Aprobarbital) {Butabarbital) {Butalbital) {Hexobarbital) {Mephobarbital) {Pentobarbital) {Phenobarbital) {Secobarbital) {Sodium thiopental) {Talbutal) {Thiobarbital)

Antihistamines edit

(Acrivastine) (Astemizole) (Azelastine) (Brompheniramine) (Carbinoxamine) (Cetirizine) (Chlorphenamine) (Clemastine) (Desloratadine) (Dimenhydrinate) (Diphenhydramine) (Doxylamine) (Loratadine) (Fexofenadine) (Meclizine) (Promethazine) (Triprolidine)

Herbal Sedatives edit

(Valerian plant) (Salvia) (Cannabis) (Datura) (Kava) (Mandrake)

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