Synthesis of Phenobarbital

IUPAC Name of Phenobarbital

5-Ethyl-5-phenyl-1,3-diazinane-2,4,6-trione
Phenobarbital, also known as phenobarbitone or phenobarb and its trade name Luminal.

Synthesis of Phenobarbital

Phenobarbital can be synthesized in number of steps from benzyl chloride. Benzyl chloride reatcts with cyanide ion to give benzyl cyanide which on hydrolysis gives phenylacetic acid which on subsquent esterification with ethanol forms ethyl phenyl acetate. Ethyl phenyl acetate on reaction with diethyloxalate in the presence of absolute ethanol and sodium metal gives diethyl phenyl oxalato acetate which on distillation at 180^oC results into Phenyl malonic ester. Phenyl malonic ester on treatment with ethyl bromide and sodium ethoxide gives ethyl phenyl malonic ester and in the last step, ethyl phenyl malonic ester condense with urea yield the official product Phenobarbital.

Therapeutic Uses of Phenobarbital

Phenobarbital slows the activity of brain and nervous system and is used for the treatment of seizures (i.e. sudden, uncontrolled electrical disturbance in the brain) and also for producing sedation during the time of anxiety.

Dose of Phenobarbital

Seizures: Adult: 1-3 mg/kg/day orally
Sedation: Adult: 30-120 mg/day orally
Hypnotic: Adult: 100-320 mg/day orally
Insomnia: 100-200 mg orally at bedtime