B.Pharm. Bachelor of Pharmacy Bachelor of Pharmacy (B.Pharm.) Pharmaceutical Chemistry 2 — Questions and Answers
Question 1: Which functional group is responsible for the acidic character of aspirin?
- Ester group
- Carboxylic acid group (Correct answer)
- Hydroxyl group
- Amide group
Correct answer: Carboxylic acid group
Aspirin contains a carboxylic acid (-COOH) group that donates a proton, conferring its acidic character.
Question 2: What is the mechanism of action of sulfonamide antibacterial drugs?
- Inhibition of DNA gyrase
- Competitive inhibition of dihydropteroate synthase (Correct answer)
- Disruption of cell membrane integrity
- Inhibition of transpeptidase
Correct answer: Competitive inhibition of dihydropteroate synthase
Sulfonamides competitively inhibit dihydropteroate synthase, blocking bacterial folate synthesis.
Question 3: Which stereochemical descriptor system is used to assign absolute configuration to chiral centers in drug molecules?
- D/L system
- R/S (Cahn-Ingold-Prelog) system (Correct answer)
- E/Z system
- α/β system
Correct answer: R/S (Cahn-Ingold-Prelog) system
The R/S system (Cahn-Ingold-Prelog rules) assigns absolute configuration based on priority of substituents around a chiral center.
Question 4: What is the role of the ester bond in prodrug design?
- To increase molecular weight
- To improve aqueous solubility permanently
- To allow hydrolysis in vivo releasing the active drug (Correct answer)
- To prevent hepatic metabolism
Correct answer: To allow hydrolysis in vivo releasing the active drug
Ester prodrugs are hydrolyzed by esterases in vivo to release the pharmacologically active parent drug.
Question 5: Which reagent is commonly used in the Folin-Ciocalteu method to quantify phenolic compounds?
- Ninhydrin
- Folin-Ciocalteu reagent (phosphomolybdotungstic acid) (Correct answer)
- Biuret reagent
- Benedict's reagent
Correct answer: Folin-Ciocalteu reagent (phosphomolybdotungstic acid)
The Folin-Ciocalteu reagent (phosphomolybdotungstic acid) is reduced by phenols to produce a blue color measured spectrophotometrically.
Question 6: What is the pKa significance in drug absorption across biological membranes?
- It determines molecular weight
- It determines the fraction of drug in unionized form at a given pH (Correct answer)
- It predicts protein binding affinity
- It defines drug solubility in lipids directly
Correct answer: It determines the fraction of drug in unionized form at a given pH
The Henderson-Hasselbalch equation uses pKa and pH to calculate the ionized/unionized ratio, which governs membrane permeability.
Question 7: In organic pharmaceutical chemistry, which reaction converts a primary amine to a diazonium salt?
- Acylation
- Nitration
- Diazotization with NaNO2/HCl (Correct answer)
- Hofmann rearrangement
Correct answer: Diazotization with NaNO2/HCl
Treatment of primary aromatic amines with sodium nitrite and hydrochloric acid at 0–5°C produces diazonium salts.
