Medicinal Chemistry MCQs SAR Related Pharmacy License and Loksewa Exam

Medicinal Chemistry SAR related MCQs for Pharmacy License and Pharmacy Loksewa Exam.

1. Which feature is essential for the activity of local anesthetics?
A) Ester or amide linkage
B) Phenol ring
C) Halogen substitution
D) Carboxylic acid group
Correct Answer: A)

2. The aromatic ring in local anesthetics is important for which property?
A) Solubility
B) Lipophilicity
C) Metabolism
D) Ionization
Correct Answer: B)

3. Which modification enhances the potency and duration of action in local anesthetics?
A) Addition of a bulky group to the amine
B) Introduction of an ester group
C) Substitution on the para position of the aromatic ring
D) Reduction of the aromatic ring
Correct Answer: C)

4. The primary difference between ester and amide local anesthetics is related to their:
A) Lipid solubility
B) Duration of action
C) Mechanism of action
D) Stability in plasma
Correct Answer: D)

5. In the SAR of local anesthetics, the terminal amine group primarily influences:
A) Potency
B) Duration of action
C) Ionization and interaction with the receptor
D) Lipophilicity
Correct Answer: C)

6. Which property of local anesthetics allows them to penetrate neuronal membranes?
A) Hydrophilicity
B) High ionization
C) Lipophilicity
D) Protein binding
Correct Answer: C)

7. Amide-linked local anesthetics typically have longer durations of action because they are:
A) Less lipophilic
B) More resistant to hydrolysis
C) Poorly bound to plasma proteins
D) Rapidly excreted by the kidneys
Correct Answer: B)

8. Increasing the alkyl substitution on the nitrogen atom in local anesthetics generally:
A) Decreases lipid solubility
B) Increases potency
C) Reduces toxicity
D) Shortens the duration of action
Correct Answer: B)

9. The presence of an electron-donating group on the aromatic ring of a local anesthetic generally:
A) Decreases the anesthetic potency
B) Increases the stability of the molecule
C) Increases the ionization of the drug
D) Enhances the lipophilicity and potency
Correct Answer: D)

10. Which modification in the SAR of local anesthetics typically increases the metabolic rate by plasma esterases?
A) Introduction of a bulky group
B) Incorporation of an ester linkage
C) Halogenation of the aromatic ring
D) Methylation of the amine group
Correct Answer: B)

11. Which structural feature is most crucial for the direct-acting activity of sympathomimetic amines?
A) Catechol ring
B) Ester linkage
C) Amide group
D) Carboxylic acid group
Correct Answer: A)

12. The presence of a hydroxyl group on the β-carbon of a sympathomimetic amine typically:
A) Reduces receptor affinity
B) Enhances α-adrenergic activity
C) Increases β-adrenergic selectivity
D) Decreases oral bioavailability
Correct Answer: C)

13. Which modification increases the selectivity of sympathomimetic agents for β2-receptors?
A) N-substitution with a large alkyl group
B) Removal of the hydroxyl groups on the aromatic ring
C) Introduction of a methyl group at the α-carbon
D) Adding a carboxyl group
Correct Answer: A)

14. In sympathomimetic drugs, increasing the size of the alkyl group on the nitrogen atom usually:
A) Increases α-adrenergic activity
B) Increases β-adrenergic selectivity
C) Decreases potency
D) Increases duration of action
Correct Answer: B)

15. Substitution of the hydroxyl groups on the catechol ring of sympathomimetic agents generally results in:
A) Increased affinity for α-receptors
B) Decreased susceptibility to COMT metabolism
C) Enhanced lipophilicity
D) Decreased potency
Correct Answer: B)

16. Which structural change in sympathomimetic agents enhances CNS penetration?
A) Reduction of hydroxyl groups
B) Increase in molecular size
C) Addition of an amide group
D) Hydroxylation of the aromatic ring
Correct Answer: A)

17. The presence of a methyl group on the α-carbon of sympathomimetic amines primarily affects:
A) β1-adrenergic selectivity
B) Duration of action
C) Resistance to MAO degradation
D) Lipophilicity
Correct Answer: C)

18. Which modification in the SAR of sympathomimetics increases resistance to COMT?
A) Removal of the catechol hydroxyl groups
B) Addition of a hydroxyl group to the aromatic ring
C) Introduction of an ester group
D) Addition of a bulky alkyl group on nitrogen
Correct Answer: A)

19. In the SAR of sympathomimetic agents, a bulky N-substitution typically:
A) Reduces oral bioavailability
B) Increases β-adrenergic selectivity
C) Enhances α-adrenergic activity
D) Decreases CNS penetration
Correct Answer: B)

20. The presence of two hydroxyl groups on the aromatic ring of a sympathomimetic amine is crucial for:
A) Lipophilicity
B) CNS penetration
C) High potency at β-receptors
D) Rapid metabolism by COMT
Correct Answer: D)

21. Which structural feature is critical for β-blocker activity?
A) Aromatic ring attached to an amine group
B) Catechol ring
C) Ester linkage
D) Carbonyl group
Correct Answer: A)

22. Selective β1-blockers typically have which structural characteristic?
A) Bulky alkyl group on the nitrogen
B) Ether linkage between the aromatic ring and amine
C) Substitution on the para position of the aromatic ring
D) Methyl group at the α-carbon
Correct Answer: C)

23. The introduction of an isopropyl group on the nitrogen of a β-blocker primarily affects:
A) Selectivity for β2-receptors
B) Oral bioavailability
C) Duration of action
D) β1-selectivity
Correct Answer: D)

24. In non-selective β-blockers, the presence of which group enhances lipophilicity and CNS penetration?
A) Ester group
B) Aromatic ring
C) Hydroxyl group
D) Ether linkage
Correct Answer: B)

25. Which modification is likely to increase the β1-selectivity of a β-blocker?
A) Bulky N-substitution
B) Para substitution on the aromatic ring
C) Introduction of an ether linkage
D) Addition of a catechol ring
Correct Answer: B)

26. The presence of a hydroxyl group on the side chain of a β-blocker generally increases:
A) β2-selectivity
B) Lipophilicity
C) β1-selectivity
D) Water solubility
Correct Answer: D)

27. Which structural characteristic of β-blockers enhances their duration of action?
A) Presence of a large alkyl group
B) Introduction of a methylene bridge
C) Addition of a carbonyl group
D) Aromatic substitution with a polar group
Correct Answer: B)

28. The presence of an ether linkage in β-blockers generally contributes to:
A) Selectivity for β2-receptors
B) Increased lipid solubility
C) Enhanced β1-receptor selectivity
D) Increased hydrophilicity
Correct Answer: C)

29. Which feature in the SAR of β-blockers is important for selective β1-blockade?
A) Substitution at the para position
B) Isopropyl group on nitrogen
C) Presence of a carbonyl group
D) Catechol ring
Correct Answer: A)

30. The substitution of a phenyl group in the β-blocker structure generally affects:
A) β1-selectivity
B) Lipophilicity and CNS penetration
C) Oral bioavailability
D) Resistance to metabolism
Correct Answer: B)

31. Which structural feature is essential for muscarinic receptor activity in parasympathomimetic agents?
A) Ester group
B) Tertiary amine
C) Quaternary ammonium group
D) Hydroxyl group
Correct Answer: C)

32. The presence of a carbamate group in parasympathomimetic agents typically:
A) Increases muscarinic receptor selectivity
B) Decreases susceptibility to hydrolysis
C) Enhances CNS penetration
D) Reduces oral bioavailability
Correct Answer: B)

33. In the SAR of parasympathomimetic agents, a quaternary ammonium group is crucial for:
A) CNS activity
B) Binding to nicotinic receptors
C) Muscarinic receptor selectivity
D) Resistance to cholinesterase degradation
Correct Answer: C)

34. Which modification in the structure of parasympathomimetic agents enhances oral bioavailability?
A) Reduction of molecular weight
B) Esterification of the hydroxyl group
C) Introduction of a bulky alkyl group
D) Conversion to a tertiary amine
Correct Answer: D)

35. The introduction of a methyl group on the nitrogen atom of a parasympathomimetic agent typically affects:
A) Muscarinic receptor selectivity
B) Nicotinic receptor binding
C) Duration of action
D) CNS penetration
Correct Answer: A)

36. Which structural change increases the resistance of parasympathomimetic agents to cholinesterase degradation?
A) Introduction of a carbamate group
B) Substitution of a hydroxyl group
C) Addition of an amide linkage
D) Quaternary ammonium substitution
Correct Answer: A)

37. The presence of a quaternary ammonium group in parasympathomimetic agents generally results in:
A) Poor CNS penetration
B) High oral bioavailability
C) Prolonged duration of action
D) Selective nicotinic receptor activity
Correct Answer: A)

38. Which modification enhances the selectivity of parasympathomimetic agents for muscarinic receptors?
A) Tertiary amine formation
B) Introduction of a bulky substituent
C) Presence of a quaternary ammonium group
D) Carbamate linkage
Correct Answer: C)

39. In the SAR of parasympathomimetic agents, the introduction of an ether group typically:
A) Increases selectivity for nicotinic receptors
B) Reduces muscarinic activity
C) Enhances stability against hydrolysis
D) Decreases potency
Correct Answer: C)

40. Which structural feature is common in parasympathomimetic agents to enhance muscarinic activity?
A) Quaternary ammonium group
B) Ester linkage
C) Tertiary amine
D) Catechol ring
Correct Answer: A)

41. Which structural feature is crucial for the sedative-hypnotic activity of barbiturates?
A) Urea linkage
B) Thiobarbiturate ring
C) Carbonyl group at C-2
D) Alkyl substitution at C-5
Correct Answer: D)

42. The introduction of a sulfur atom at position 2 of the barbiturate ring generally:
A) Increases lipid solubility
B) Decreases sedative potency
C) Enhances water solubility
D) Reduces CNS penetration
Correct Answer: A)

43. The alkyl substitution at C-5 in barbiturates primarily affects:
A) Oral bioavailability
B) Duration of action
C) Lipid solubility and potency
D) CNS penetration
Correct Answer: C)

44. Which modification in barbiturates increases the hypnotic potency?
A) Replacement of oxygen with sulfur at C-2
B) Introduction of a phenyl group at C-5
C) Methylation at N-1
D) Addition of a hydroxyl group
Correct Answer: A)

45. The replacement of oxygen with sulfur at the C-2 position in barbiturates forms:
A) Phenobarbital
B) Secobarbital
C) Thiopental
D) Methohexital
Correct Answer: C)

46. The presence of a nitro group at the 7-position in benzodiazepines typically:
A) Increases potency
B) Decreases CNS penetration
C) Enhances metabolism
D) Reduces sedative effects
Correct Answer: A)

47. Which structural feature is essential for the activity of benzodiazepines?
A) Halogen substitution at the 7-position
B) Methyl group at the 3-position
C) Ketone group at the 4-position
D) Ester linkage
Correct Answer: A)

48. The introduction of a halogen atom at the 7-position of the benzodiazepine ring typically:
A) Decreases lipophilicity
B) Increases potency and CNS penetration
C) Enhances water solubility
D) Reduces receptor affinity
Correct Answer: B)

49. In benzodiazepines, the substitution of a hydroxyl group at the 3-position generally:
A) Increases water solubility
B) Decreases potency
C) Reduces metabolism
D) Enhances lipophilicity
Correct Answer: A)

50. Which modification in morphine analogues increases the analgesic potency?
A) Introduction of a methyl group on the nitrogen atom
B) Hydroxylation at position 3
C) Removal of the 6-hydroxyl group
D) Addition of a methoxy group at position 3
Correct Answer: C)

51. Which structural feature is essential for the opioid activity of morphine?
A) 3-hydroxyl group
B) 6-methyl group
C) Ester linkage
D) Halogen substitution
Correct Answer: A)

52. Which modification in the morphine structure increases its analgesic potency?
A) N-demethylation
B) Hydrogenation of the 7,8 double bond
C) Addition of a methoxy group at position 3
D) Removal of the 6-hydroxyl group
Correct Answer: D)

53. The presence of which functional group at position 17 of morphine reduces its opioid activity?
A) Methyl group
B) Hydroxyl group
C) Ethyl group
D) Allyl group
Correct Answer: D)

54. Conversion of the 3-hydroxyl group in morphine to a methoxy group results in which compound?
A) Codeine
B) Heroin
C) Hydromorphone
D) Oxycodone
Correct Answer: A)

55. Which modification in the morphine structure results in the formation of heroin?
A) N-methylation
B) O-methylation at position 3
C) Acetylation at positions 3 and 6
D) Reduction of the 6-hydroxyl group
Correct Answer: C)

56. The reduction of the 7,8 double bond and oxidation of the 6-hydroxyl group in morphine leads to the formation of:
A) Morphine-6-glucuronide
B) Codeine
C) Oxymorphone
D) Hydromorphone
Correct Answer: D)

57. Which modification increases the lipophilicity and CNS penetration of morphine?
A) O-acetylation
B) N-demethylation
C) 6-hydroxyl group removal
D) 3-hydroxyl group removal
Correct Answer: A)

58. Which structural feature of morphine is crucial for binding to the mu-opioid receptor?
A) 4,5-epoxide ring
B) 3-hydroxyl group
C) 6-hydroxyl group
D) Ether bridge
Correct Answer: B)

59. Replacing the N-methyl group in morphine with a cyclopropylmethyl group typically results in:
A) Increased potency
B) Antagonistic activity
C) Decreased analgesic activity
D) Enhanced lipophilicity
Correct Answer: B)

60. The conversion of morphine to naloxone involves which structural change?
A) N-demethylation
B) Addition of an allyl group at the nitrogen
C) Acetylation of the hydroxyl groups
D) Methylation of the phenolic hydroxyl group
Correct Answer: B)