SECOBARBITAL Synthesis, SAR, MCQ,Structure,Chemical Properties and Therapeutic Uses

SECOBARBITAL Synthesis, SAR, MCQ,Structure,Chemical Properties and Therapeutic Uses


IUPAC nomenclature



Secobarbital is a barbiturate sedative-hypnotic.

Physiochemical Properties

1 Molecular weight 238.28g/mol
2 Physical appearance White amorphous or crystalline powder
3 Melting point 100°C
4 Octanol/water partition coefficient 1.97
5 Solubility Very soluble in water
6 Presence of ring Pyrimidine
7 Number of chiral centers 2


Mechanism of Action

i. Drug binds with different binding sites associated with chloride ionopore at the GABAA

ii. This results in increase in the duration of time for the opening of the chloride ionopore.

iii. As a result, the post synaptic inhibitory effect of GABA in the thalamus is prolonged.


Structure Activity Relationship

  • Tri-keto form is most stable in aqueous solution.
  • 4,6-dialcoholic tautomeric forms are least stable in aqueous solution.
  • 5,5-disubstituted barbituric acid is the prime requirement for the barbiturates to be sedative hypnotics.
  • Esterification of either of the 1,3-diazine nitrogens decreases hypnotic activity.
  • Substitution of either of the 1,3-diazine nitrogens with aliphatic carbons retains the anticonvulsive properties.
  • Esterification of the 5th-position substituents yields agents with analgesic activity but with weak hypnotic properties.
  • Introduction of the polar functional group at the 5th– position yields compounds which are fully devoid of sedative-hypnotic or anticonvulsive activity.
  • As the number of carbons at R2 carbon increases, the lipophillicity of the drug increases.
  • Modification of the 2nd-position oxygen of the barbiturate backbone with sulfur atom yields thiobarbiturate derivatives with increased lipophillicity, shorter duration of action, faster time of onset compared to oxy-derivative. [1]


Method of synthesis

Secobarbital can be synthesized by reaction of α-allyl-α-(1-methylbutyl)-malonic ester with urea.[2]

Therapeutic Uses

Secobarbital is used for:

  • Treatment of seizures
  • For producing sedation during the time of anxiety.


Side Effects

Side effects of Secobarbital are:

  • Insomnia
  • Dizziness
  • Drowsiness
  • Loss of coordination
  • Nausea
  • Vomiting
  • Constipation
  • Restlessness
  • Headache
  • Loss of appetite
  • Pale skin
  • Shallow breathing



 Q.1 Choose the correct statements related to the physicochemical properties of drug secobarbital-

I. Molecular weight is 238.28 gm/mol

II. White amorphous crystalline powder

III. It is very soluble in water

IV. Melting point is 325K 

a) I, II

b) I, II, III

c) III, IV

d) I, III, IV

Q.2 Match the following of the drugs with their correct Trade names.

i. Secobarbital A. Mustine
ii. Mechlorethamine B. Ipamide
iii. Cyclophosphamide C. Saconal
iv. Ifosfamide D. Cycloxan

 a) i-B, ii-C, iii-D, iv-A

b) i-B, ii-C, iii-A, iv-D

c) i-C, ii-A, iii-D, iv-B

d) i-A, ii-D, iii-B, iv-C

Q.3 Effect produced due to binding of secobarbital with GABAA receptor??

a) Increase in GABA affinity for GABA receptor

b) Decrease in GABA affinity for GABA receptor

c) Blocking of GABA receptor for GABA

d) None of the above

Q.4 Correct sequence for True/false for the classification of the drug can be?

  • Secobarbital: Neuraminidase inhibitor analogue
  • Phenobarbital: Non-nucleoside reverse transcriptase inhibitor
  • Ribavirin: Conventional nucleoside analogue
  • Tipranavir: HIV protease inhibitor





Q.5 Esterification of either of the 1,3-diazine nitrogens of secobarbital results in?

a) Decrease in hypnotic activity

b) Increase in hypnotic activity

c) Bioavailability increases

d) Bioavailability decreases

Q.6 Type/s of ring present in the structure of secobarbital?

I. Pyrimidine

II. Indole

III. Benzene

a) II, III

b) I, II

c) I

d) I, II, III 

Q.7 Side effect of drug Secobarbital?

a) Insomnia

b) Dizziness

c) Loss of coordination

d) All of the above


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[1] Lemke TL, Zito SW, Roche VF, Williams DA. Essentials of Foye’s principles of medicinal chemistry. Wolters Kluwer; 2017, 490-91

[2] Vardanyan R, Hruby V. Synthesis of essential drugs. Elsevier; 2006 Mar 10.

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