top of page
Search
1 min read

Barbital: Chemical Structure, Mechanism of Action, Structure-Activity Relationship, Synthesis, Uses & Side Effects

Chemical Structure:

  • C8H12N2O3

Chemical Structure
Chemical Structure

Mechanism of Action:

  • Barbital is a barbiturate that works by enhancing the action of GABA, a neurotransmitter that inhibits brain activity.

  • This results in sedative and hypnotic effects.

Structure-Activity Relationship (SAR) of Barbital:

1.Barbituric Acid Core:

  • Barbital, like all barbiturates, is derived from barbituric acid, which consists of a urea and malonic acid derivative forming a pyrimidine-dione ring system.

  • This core is crucial for the biological activity of barbiturates.

2.Substitutions at C5:

  • The presence of alkyl or aryl groups at the C5 position of the barbituric acid ring enhances the lipid solubility and, consequently, the potency and duration of action.

  • Barbital has ethyl groups at this position.

3.Hydrogen Bonding:

  • The ability of barbiturates to engage in hydrogen bonding through the NH groups in the barbituric acid ring influences their interaction with the GABA-A receptor and their potency.

4.Lipophilicity:

  • The overall lipophilicity of the molecule affects its onset and duration of action.

  • For Barbital, the ethyl groups provide moderate lipophilicity, contributing to its sedative effect.

SAR of Barbital
SAR of Barbital

Synthesis of Barbital (Chemical Reaction):

The synthesis of Barbital is a classic example of barbiturate synthesis, involving the condensation of urea with diethyl malonate:

1.Condensation Reaction:

  • Diethyl malonate + Urea → (acidic conditions) Barbital

  • In this reaction, diethyl malonate and urea are combined under acidic conditions.

  • The malonate provides the carbon skeleton for the barbituric acid core, while urea provides the nitrogen atoms.

  • The reaction typically involves heating the reactants with an acid catalyst to facilitate the condensation and cyclization into the barbiturate ring system.

Uses:

  • It was formerly used as a sedative and hypnotic.

  • However, it's seldom used today due to the risk of abuse and the availability of safer alternatives.

Side Effects:

  • Potential side effects include drowsiness, dizziness, nausea, and in severe cases, respiratory depression, dependence, and withdrawal symptoms.

bottom of page