Title: Cyclopentobarbital
CAS Registry Number: 76-68-6
CAS Name: 5-(2-Cyclopenten-1-yl)-5-(2-propenyl)-2,4,6(1H,3H,5H)-pyrimidinetrione
Additional Names: 5-allyl-5-(2-cyclopenten-1-yl)barbituric acid
Trademarks: Cyclopal (Kytta-Siegfried)
Molecular Formula: C12H14N2O3
Molecular Weight: 234.25
Percent Composition: C 61.53%, H 6.02%, N 11.96%, O 20.49%
Literature References: Prepd by condensing the ethyl ester of cyclopentenylmalonic acid with urea: Compagnie de Bethune: DE 589947 (1930), Frdl. 19, 1198; GB 349455; FR 38680.
Properties: Crystals, mp 139-140°. Bitter taste. Slightly sol in cold water; moderately sol in hot water. Freely sol in alcohol, organic solvents.
Melting point: mp 139-140°
NOTE: This is a controlled substance (depressant): 21 CFR, 1308.13.
Therap-Cat: Sedative, hypnotic.
Keywords: Sedative/Hypnotic; Barbituric Acid Derivatives.
Status: This monograph has been retired and is no longer subject to revision or update.
Cyclopentolate Cyclophosphamide Cyclopropane Cyclopropyl Methyl Ether Cyclorphan

Systematic (IUPAC) name
Clinical data
Legal status  ?
CAS number 76-68-6
302-34-1 (sodium)
ATC code None
PubChem CID 6454
ChemSpider 6212 YesY
Synonyms Allylpental, Cyclopental, 5-Allyl-5-Δ2-Cyclopentenyl Barbituric Acid
Chemical data
Formula C12H14N2O3 
Mol. mass 234.251 g/mol
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Cyclopentobarbital sodium (Cyclopal, Dormisan) is a barbiturate derivative invented in the 1940s.[1] It has sedative and anticonvulsant properties, and was used primarily as an anaesthetic in veterinary medicine.[2] Cyclopal is considered similar in effects to phenobarbital but lasts almost three times as long, and is considered a long-acting barbiturate with a fairly slow onset of action.