Structural Formula Vector Image
Title: Phenobarbital
CAS Registry Number: 50-06-6
CAS Name: 5-Ethyl-5-phenyl-2,4,6(1H,3H,5H)-pyrimidinetrione
Additional Names: 5-ethyl-5-phenylbarbituric acid; phenylethylmalonylurea; phenobarbitone
Trademarks: Agrypnal (Eggochemia); Barbiphenyl (L×kefarmos); Barbipil (Conal); Gardenal (Specia); Luminal (Desitin); Phenobal (Fujinaga)
Molecular Formula: C12H12N2O3
Molecular Weight: 232.24
Percent Composition: C 62.06%, H 5.21%, N 12.06%, O 20.67%
Literature References: Prepn: DE 247952 (1911 to Bayer); Hoerlein, US 1025872 (1912), Frdl. 11, 926; Chem. Zentralbl. 1912, II, 212; Chamberlain et al., J. Am. Chem. Soc. 57, 352 (1935); Inman, Bitler, US 2358072 (1944 to Kay-Fries Chem.); J. T. Pinhey, B. A. Rowe, Tetrahedron Lett. 21, 965 (1980). Toxicity data: Schaffarzick, Brown, Science 116, 663 (1952); E. I. Goldenthal, Toxicol. Appl. Pharmacol. 18, 185 (1971). Series of articles on pharmacology and mechanism of antiepileptic action: Adv. Neurol. 27, 473-562 (1980). Clinical evaluation in febrile convulsions: R. W. Newton, Arch. Dis. Child. 63, 1189 (1988). Comprehensive description: M. K. C. Chao et al., Anal. Profiles Drug Subs. 7, 359-399 (1978).
Properties: Crystals (3 different phases), mp 174-178°. uv max (pH 10 buffer): 240 nm (A1%1cm 431); (0.1N NaOH): 256 nm (A1%1cm 314). Slightly bitter taste. One gram dissolves in about one liter of water, 8 ml alc, 40 ml chloroform, 13 ml ether, about 700 ml benzene. Soluble in alkali hydroxides and carbonates. A satd aq soln is acid to litmus. pK1 7.3, pK2 11.8. LD50 orally in rats: 162 ±14 mg/kg (Goldenthal).
Melting point: mp 174-178°
pKa: pK1 7.3, pK2 11.8
Absorption maximum: uv max (pH 10 buffer): 240 nm (A1%1cm 431); (0.1N NaOH): 256 nm (A1%1cm 314)
Toxicity data: LD50 orally in rats: 162 ±14 mg/kg (Goldenthal)
Derivative Type: Sodium salt
CAS Registry Number: 57-30-7
Additional Names: Sol phenobarbital; sol phenobarbitone
Molecular Formula: C12H11N2NaO3
Molecular Weight: 254.22
Percent Composition: C 56.69%, H 4.36%, N 11.02%, Na 9.04%, O 18.88%
Properties: Bitter, slightly hygroscopic crystals or white powder. One gram dissolves in about 1 ml water, about 10 ml alcohol. Insol in ether or chloroform. Aq solns are alkaline to litmus and phenolphthalein, pH ~9.3. LD50 orally in rats: 660 mg/kg (Schaffarzick, Brown).
Toxicity data: LD50 orally in rats: 660 mg/kg (Schaffarzick, Brown)
NOTE: This is a controlled substance (depressant): 21 CFR, 1308.14.
Therap-Cat: Anticonvulsant; sedative; hypnotic.
Therap-Cat-Vet: Anticonvulsant; sedative.
Keywords: Anticonvulsant; Sedative/Hypnotic; Barbituric Acid Derivatives.

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