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chloral hydrate (n.)
1.a colorless crystalline drug used as a sedative; irritates the stomach and can be addictive
Chloral Hydrate (n.)
1.(MeSH)A hypnotic and sedative used in the treatment of INSOMNIA.
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Chloral hydrate | |
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2,2,2-trichloroethane-1,1-diol |
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Other names
Trichloroacetaldehyde monohydrate |
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Identifiers | |
CAS number | 302-17-0 |
PubChem | 2707 |
ChemSpider | 2606 |
UNII | 418M5916WG |
DrugBank | DB01563 |
KEGG | D00265 |
ChEBI | CHEBI:28142 |
ChEMBL | CHEMBL455917 |
Jmol-3D images | Image 1 |
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Properties | |
Molecular formula | C2H3Cl3O2 |
Molar mass | 165.40 g/mol |
Appearance | Colorless solid |
Density | 1.91 g/cm3 |
Melting point |
57 °C, 330 K, 135 °F |
Boiling point |
98 °C, 371 K, 208 °F |
Acidity (pKa) | 9.66, 11.0[1] |
Pharmacology | |
Bioavailability | well absorbed |
Routes of administration |
Oral codeine/syrup, rectal suppository |
Metabolism | converted to trichloroethanol, hepatic and renal |
Elimination half-life |
8–10 hours in plasma |
Excretion | bile, feces, urine (various metabolites not unchanged) |
Legal status | |
Pregnancy category |
C(US) |
Hazards | |
MSDS | External MSDS |
EU classification | Harmful (Xn) |
R-phrases | R22 R36 R37 R38 |
Related compounds | |
Related compounds | Chloral, chlorobutanol |
(verify) (what is: / ?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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Infobox 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.[2][3] Its sedative properties were first published in 1869 and subsequently, because of its easy synthesis, its use was widespread.[4] It was widely used recreationally 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[citation needed]. More reputable uses of chloral hydrate include its use as a clearing agent for chitin and fibers and as a key ingredient in Hoyer's mounting medium, which is used to prepare permanent or semipermanent microscope slides of small organisms, histological sections, and chromosome squashes.
It is, together with chloroform, a minor side-product of the chlorination of water when organic residues are present in the water, though concentrations rarely exceed 5 micrograms per litre (µg/L).[citation needed]
Contents |
Chloral hydrate is produced from chlorine and ethanol in acidic solution. In basic conditions the haloform reaction takes place and chloroform is produced.
Chloral hydrate is a starting point for the synthesis of more complex chemicals. 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:[5]
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 in the mid-20th century by barbiturates[6] 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[citation needed]. It is also still used as a sedative prior to EEG procedures, as it is one of the few available sedatives that does not suppress epileptiform discharges.[7]
In therapeutic doses for insomnia chloral hydrate is effective within 60 minutes, it is metabolized within four minutes into trichloroethanol by erythrocytes and plasma esterases and many hours later into trichloroacetic acid. It has a very narrow therapeutic window making this drug difficult to use. Higher doses can depress respiration and blood pressure.
Long-term use of chloral hydrate is associated with a rapid development of tolerance to its effects and possible addiction as well as adverse effects including rashes, gastric discomfort and severe renal, cardiac and hepatic failure.[8]
Acute overdosage is often characterized by nausea, vomiting, confusion, convulsions, slow and irregular breathing, cardiac arrhythmia, and coma. The plasma, serum or blood concentrations of chloral hydrate and/or trichloroethanol, its major active metabolite, may be measured to confirm a diagnosis of poisoning in hospitalized patients or to aid in the medicolegal investigation of fatalities. Accidental overdosage of young children undergoing simple dental or surgical procedures has occurred. Hemodialysis has been used successfully to accelerate clearance of the drug in poisoning victims.[9]
Chloral hydrate exerts its pharmacological properties via enhancing the GABA receptor complex.[10] It 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.[citation needed]
Chloral hydrate is a prescription-only-medicin (POM) in the Netherlands, but possession without a valid prescription will result only in seizure of the drug but not in prosecution. Production, sale and distribution are however punishable by law. It is not listed under the Opium Law, but when the intent is human consumption, it is covered by the Geneesmiddelenwet (Medicin Act).
Chloral hydrate is illegal in the United States without a 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.[11][unreliable source?]
Chloral hydrate is also controlled substance in Canada under Schedule F of the Food and Drug Regulations.[12]
Chloral hydrate is not a controlled substance in the United Kingdom.
Chloral hydrate is also an ingredient used for Hoyer's solution, a mounting medium for microscopic observation of diverse organisms such as bryophytes, ferns, seeds, and small arthropods (especially mites). One recipe for making Hoyer's is dissolving gum arabic (30.0 g) in water (50.0 mL), then adding chloral hydrate (200.0 g), and then finally adding glycerol (16.0 mL). An advantage of this medium include an excellent refraction index and clearing (macerating) properties of the small specimens (especially advantageous if specimens require observation with differential interference contrast microscopy). The major disadvantage of Hoyer's is its susceptibility to the effects of rehydration, which causes the mountant to crystallize and threatening the slide to become unusable. It is therefore absolutely necessary, after drying a mounted specimen, to thoroughly ring (2 layers are best) cover slips with a protective coating (e.g., insulating Glyptol), which prevents rehydration and mountant deterioration. Chloral hydrate reportedly does not effectively clear larger specimens, or arthropods that are more heavily sclerotized (e.g., larger insects). These should first be cleared with another product (e.g., 10% KOH or NaOH), and then mounted in Hoyer's. Other disadvantages of Hoyer's (principally due to chloral hydrate) include toxicity (see above), and procurement problems due to chloral hydrate being a controlled substance.
Media related to Chloral hydrate at Wikimedia Commons
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