Medicinal uses of thiazole MCQs With Answer

The thiazole ring is a five‑membered aromatic heterocycle containing both sulfur and nitrogen, widely used as a privileged scaffold in medicinal chemistry. For B. Pharm students, understanding the medicinal uses of thiazole and thiazole derivatives is essential: these scaffolds contribute to antibacterial, antifungal, antiviral, anti‑inflammatory and anticancer activities, influence ADME/Tox and serve as bioisosteres in drug design. Key concepts include structure, SAR, synthetic routes (e.g., α‑haloketone + thioamide condensation), metabolic pathways and analytical characterization. This focused overview will help you apply thiazole chemistry to pharmacology, formulation and safety assessment. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the thiazole ring?

• A six‑membered aromatic ring containing nitrogen and oxygen
• A five‑membered aromatic heterocycle containing sulfur and nitrogen
• A five‑membered aliphatic ring containing sulfur and oxygen
• A bicyclic heterocycle derived from pyridine

Correct Answer: A five‑membered aromatic heterocycle containing sulfur and nitrogen

Q2. Which statement best describes the aromaticity of thiazole?

• It is non‑aromatic because of sp3 hybridization
• It is aromatic with a 6 π‑electron system across the ring
• It is antiaromatic with 4 π electrons
• It is aromatic only when substituted at position 2

Correct Answer: It is aromatic with a 6 π‑electron system across the ring

Q3. Which well‑known natural molecule contains a thiazole moiety?

• Vitamin C (ascorbic acid)
• Thiamine (vitamin B1)
• Pyridoxine (vitamin B6)
• Folic acid

Correct Answer: Thiamine (vitamin B1)

Q4. A classical laboratory method to form a thiazole ring commonly involves condensation between which two types of reagents?

• α‑Haloketones and thioamides
• Aldehydes and hydrazines
• Grignard reagents and esters
• Nitriles and organolithiums

Correct Answer: α‑Haloketones and thioamides

Q5. Which of the following biological activities are commonly associated with thiazole derivatives?

• Antibacterial, antifungal and anticancer activities
• Only antihypertensive activity
• Only vitamin supplementation
• Exclusive use as anesthetics

Correct Answer: Antibacterial, antifungal and anticancer activities

Q6. Which heteroatom in thiazole is more polarizable and often contributes to soft‑metal coordination and increased lipophilicity?

• Nitrogen
• Oxygen
• Sulfur
• Fluorine

Correct Answer: Sulfur

Q7. What is a major medicinal chemistry reason to incorporate a thiazole ring into a lead molecule?

• To increase molecular flexibility and reduce planarity
• To introduce a rigid, aromatic scaffold that can enhance binding and lipophilicity
• To guarantee high aqueous solubility without modification
• To always make the compound acidic

Correct Answer: To introduce a rigid, aromatic scaffold that can enhance binding and lipophilicity

Q8. Which analytical techniques are most informative to confirm formation of a thiazole ring during synthesis?

• Thin‑layer chromatography (TLC) only
• 1H/13C NMR spectroscopy and mass spectrometry
• Paper chromatography and melting point alone
• Colorimetric tests only

Correct Answer: 1H/13C NMR spectroscopy and mass spectrometry

Q9. In typical aromatic substitution chemistry of thiazole, electrophilic substitution most readily occurs at which ring position?

• Position 4 exclusively
• Position 5 (adjacent to carbon next to sulfur)
• Position 2 exclusively
• At the nitrogen atom by protonation

Correct Answer: Position 5 (adjacent to carbon next to sulfur)

Q10. Sulfathiazole is an example of a thiazole‑containing drug historically used as which class of antimicrobial?

• Macrolide antibiotic
• Sulfonamide (antibacterial) that inhibits folate synthesis
• Beta‑lactamase inhibitor
• Aminoglycoside antibiotic

Correct Answer: Sulfonamide (antibacterial) that inhibits folate synthesis

Q11. Which functional role does the nitrogen of the thiazole ring most commonly serve in drug‑target interactions?

• Strong hydrogen bond donor
• Hydrogen bond acceptor and aromatic electron contributor
• Permanent positive charge to bind anionic pockets
• Metal chelator stronger than carboxylates

Correct Answer: Hydrogen bond acceptor and aromatic electron contributor

Q12. Thiazole rings are generally ionization state at physiological pH:

• Highly basic and fully protonated at pH 7.4
• Weakly basic and largely unprotonated (neutral) at pH 7.4
• Strongly acidic and deprotonated at pH 7.4
• Always zwitterionic at physiological pH

Correct Answer: Weakly basic and largely unprotonated (neutral) at pH 7.4

Q13. Which metabolic transformation is commonly observed for sulfur‑containing heterocycles like thiazoles?

• Conjugation to form persistent radicals only
• S‑oxidation to sulfoxides or sulfones increasing polarity
• Dehalogenation at the nitrogen atom
• No metabolism due to extreme stability

Correct Answer: S‑oxidation to sulfoxides or sulfones increasing polarity

Q14. In medicinal chemistry, thiazole is often used as a bioisostere for which other heterocycle?

• Oxazole (oxygen replacing sulfur)
• Alkane chain
• Carboxylic acid
• Epoxide

Correct Answer: Oxazole (oxygen replacing sulfur)

Q15. Thiazole orange is an example of a thiazole derivative used primarily as:

• An anti‑hypertensive agent
• A fluorescent dye/probe for nucleic acids
• A peptide that inhibits proteases
• A radiolabeled tracer for PET imaging

Correct Answer: A fluorescent dye/probe for nucleic acids

Q16. For a neutral thiazole‑containing drug with poor aqueous solubility, which formulation strategy is often most appropriate?

• Salt formation with mineral acids
• Prodrug design or cyclodextrin complexation
• Adding excess sodium chloride to the tablet
• Avoid formulation changes since solubility cannot be improved

Correct Answer: Prodrug design or cyclodextrin complexation

Q17. Which spectroscopic region is useful to monitor the C=N stretching vibration of thiazole rings?

• Far‑IR region below 400 cm‑1
• Mid‑IR around 1600 cm‑1
• Microwave region only
• Visible region around 500–700 nm

Correct Answer: Mid‑IR around 1600 cm‑1

Q18. Thiazole derivatives as kinase inhibitors is an example of which drug discovery application?

• Targeting membrane lipids exclusively
• Modulating intracellular signaling enzymes in cancer and inflammation
• Replacing antibiotics in all treatments
• Serving only as dietary supplements

Correct Answer: Modulating intracellular signaling enzymes in cancer and inflammation

Q19. Which statement about the electron density distribution of thiazole is correct?

• Nitrogen is the only electron‑rich atom and sulfur has no lone pairs
• Both nitrogen and sulfur contribute lone pairs, with sulfur being more polarizable
• Thiazole has no heteroatom lone pairs and behaves like benzene
• Only carbon atoms contribute electrons for aromaticity

Correct Answer: Both nitrogen and sulfur contribute lone pairs, with sulfur being more polarizable

Q20. Which experimental method would you choose to evaluate potential CYP‑mediated metabolism of a thiazole drug candidate?

• Cellulose electrophoresis
• Human liver microsome assay with metabolite identification by LC‑MS
• Paper chromatography only
• Acid‑base titration

Correct Answer: Human liver microsome assay with metabolite identification by LC‑MS

Q21. Which structural change often increases metabolic stability of a thiazole derivative against oxidative metabolism?

• Adding metabolically labile benzylic hydrogens
• Introducing fluorine at labile positions
• Removing steric hindrance around vulnerable carbons
• Replacing aromatic rings with aliphatic chains

Correct Answer: Introducing fluorine at labile positions

Q22. In drug design, replacing a phenyl ring with a thiazole is often done to achieve which effect?

• Increase molecular flexibility dramatically
• Reduce aromaticity to zero
• Introduce heteroatom interactions and modulate lipophilicity
• Guarantee oral bioavailability without further changes

Correct Answer: Introduce heteroatom interactions and modulate lipophilicity

Q23. Which position on the thiazole ring is most commonly substituted to modulate target binding and steric fit in medicinal chemistry?

• Position 1 (sulfur) directly
• Position 2 (alpha to nitrogen)
• The ring cannot be substituted at any position
• Only the nitrogen atom can be alkylated

Correct Answer: Position 2 (alpha to nitrogen)

Q24. Which of the following safety assays is particularly relevant for preclinical evaluation of thiazole drug candidates due to possible off‑target effects?

• Bacterial fermentation test only
• hERG (cardiac) liability and genotoxicity assays
• Color stability under sunlight only
• pH titration curve alone

Correct Answer: hERG (cardiac) liability and genotoxicity assays

Q25. Compared to pyridine, the basicity of thiazole’s nitrogen is generally:

• Stronger (higher pKa of conjugate acid)
• Similar in all cases
• Weaker (lower pKa of conjugate acid)
• Completely non‑ionizable under any pH

Correct Answer: Weaker (lower pKa of conjugate acid)

Q26. Which synthetic transformation would you use to selectively oxidize a thiazole sulfur to a sulfone during lead optimization?

• Hydrogenation with Pd/C
• Oxidation with m‑CPBA or peracids
• Reduction with LiAlH4
• Grignard addition at the nitrogen

Correct Answer: Oxidation with m‑CPBA or peracids

Q27. Which of the following is a common ADME concern specific to many thiazole derivatives?

• Excessive rapid renal clearance due to high polarity
• CYP‑mediated bioactivation to reactive metabolites causing idiosyncratic toxicity
• Absolute incapacity to cross biological membranes
• No absorption in any mammalian species

Correct Answer: CYP‑mediated bioactivation to reactive metabolites causing idiosyncratic toxicity

Q28. Which of the following is a chemical isomer of thiazole with adjacent N and S atoms?

• Pyridine
• Isothiazole
• Oxazole
• Imidazole

Correct Answer: Isothiazole

Q29. Which property of thiazole often leads medicinal chemists to use it when designing CNS‑penetrant drugs?

• Very high aqueous solubility
• Neutral aromaticity and increased lipophilicity that can aid BBB penetration
• Permanent positive charge that prevents BBB passage
• Large molecular weight that blocks distribution

Correct Answer: Neutral aromaticity and increased lipophilicity that can aid BBB penetration

Q30. For thiazole derivatives used as antimicrobials, one common mechanism (as with thiazole‑containing sulfonamides) is:

• Inhibition of dihydropteroate synthase (folate pathway)
• Blocking of microtubule polymerization exclusively
• Direct DNA alkylation only
• Chelation of calcium in the cell wall

Correct Answer: Inhibition of dihydropteroate synthase (folate pathway)

Q31. Which molecular property is most likely to change when a phenyl ring is replaced by a thiazole ring in a lead molecule?

• Molecular weight decreases dramatically to zero
• Polarity, heteroatom distribution and H‑bonding potential change
• All chiral centers are lost automatically
• The compound becomes a gas at room temperature

Correct Answer: Polarity, heteroatom distribution and H‑bonding potential change

Q32. Which formulation approach can mitigate photodegradation of UV‑absorbing thiazole dyes or drugs?

• Expose formulations to strong sunlight to pre‑stabilize them
• Use light‑protective packaging and antioxidants in the formulation
• Add peroxides to accelerate degradation
• Eliminate all excipients to reduce interactions

Correct Answer: Use light‑protective packaging and antioxidants in the formulation

Q33. In medicinal chemistry SAR, installing an electron‑withdrawing group at which thiazole position commonly affects electronic distribution and target affinity?

• Position 3 only
• Position 2 (adjacent to nitrogen), affecting electronics and binding
• Substitution never affects target affinity
• Only substituents on external alkyl chains matter

Correct Answer: Position 2 (adjacent to nitrogen), affecting electronics and binding

Q34. Which in vitro assay is useful to detect potential idiosyncratic toxicity caused by reactive metabolites of thiazole drugs?

• Ames test for mutagenicity and glutathione trapping with LC‑MS
• Simple pH measurement
• Optical rotation measurement
• Paper chromatography under UV

Correct Answer: Ames test for mutagenicity and glutathione trapping with LC‑MS

Q35. Which of the following best describes the use of thiazole as a scaffold in kinase inhibitor design?

• Thiazole cannot interact with ATP‑binding pockets
• Thiazole ring provides a planar heterocycle that can engage hinge region interactions
• Thiazole always destabilizes kinase binding
• Kinase inhibitors never contain heterocycles

Correct Answer: Thiazole ring provides a planar heterocycle that can engage hinge region interactions

Q36. During lead optimization you observe rapid clearance of a thiazole derivative in rodents. Which structural modification is most rational to reduce clearance?

• Introduce polar groups to make it extremely hydrophilic
• Block metabolically vulnerable sites with small electron‑withdrawing groups like fluorine
• Replace the thiazole with a linear alkane chain
• Completely remove heteroatoms to avoid metabolism

Correct Answer: Block metabolically vulnerable sites with small electron‑withdrawing groups like fluorine

Q37. Which statement about thiazole proton chemical shifts in 1H NMR is generally true?

• Thiazole ring protons typically appear in the high‑field aliphatic region (0–2 ppm)
• Thiazole ring protons resonate in the aromatic region (approx. 6.5–9 ppm) depending on substitution
• Thiazole has no protons so NMR is uninformative
• Thiazole protons always appear exactly at 10 ppm

Correct Answer: Thiazole ring protons resonate in the aromatic region (approx. 6.5–9 ppm) depending on substitution

Q38. Which safety precaution is important when handling thiazole intermediates and some derivatives in the organic chemistry lab?

• Work in a fume hood and use appropriate PPE due to potential toxicity and odor
• They are completely inert; no special precautions needed
• Only wear sandals and short sleeves to improve dexterity
• Store all thiazoles under direct sunlight to stabilize them

Correct Answer: Work in a fume hood and use appropriate PPE due to potential toxicity and odor

Q39. Which drug‑drug interaction risk is a concern for some thiazole derivatives based on their metabolic profile?

• Induction or inhibition of CYP enzymes leading to altered exposure of co‑medications
• Complete prevention of renal excretion of all drugs
• Instant neutralization of vaccines
• No possibility of interacting with other drugs

Correct Answer: Induction or inhibition of CYP enzymes leading to altered exposure of co‑medications

Q40. Which physicochemical property of a thiazole fragment is most tunable to optimize oral absorption?

• Molecular chirality only
• Lipophilicity (log P) and topological polar surface area (TPSA)
• The number of sulfur atoms cannot be changed
• Only the melting point can be tuned

Correct Answer: Lipophilicity (log P) and topological polar surface area (TPSA)

Q41. Which tool is particularly useful in early design to predict binding modes of thiazole‑containing ligands to protein targets?

• Computational molecular docking and structure‑based design
• Microscopy alone without structural data
• Paper chromatography
• Only human intuition without any models

Correct Answer: Computational molecular docking and structure‑based design

Q42. Which is an appropriate preformulation concern for a thiazole drug candidate intended for oral solid dosage forms?

• Assessing low aqueous solubility and potential need for solubilization strategies
• Ignoring chemical stability since heterocycles never degrade
• Assuming it will always form a stable hydrate
• Skipping dissolution testing entirely

Correct Answer: Assessing low aqueous solubility and potential need for solubilization strategies

Q43. Which of the following is a rational route to modify a thiazole lead to reduce potential reactive metabolite formation?

• Introduce electron‑withdrawing groups to reduce metabolic activation
• Increase easily oxidizable sites to encourage metabolism
• Remove all heteroatoms to make the molecule more reactive
• Convert the ring to a peroxide

Correct Answer: Introduce electron‑withdrawing groups to reduce metabolic activation

Q44. Which experimental approach helps determine whether a thiazole derivative binds covalently to a target protein?

• Incubation with the protein followed by LC‑MS analysis for adduct formation
• Measuring only UV absorbance at 260 nm
• Performing only a melting point determination
• Color change on paper strip

Correct Answer: Incubation with the protein followed by LC‑MS analysis for adduct formation

Q45. Which of the following is a documented medicinal use class where thiazole scaffolds are explored extensively?

• Antimicrobial and anticancer drug design
• Only as food preservatives
• Exclusive use in textile dyes with no biological activity
• None — thiazoles are not used in medicine

Correct Answer: Antimicrobial and anticancer drug design

Q46. Which modification is a common medicinal chemistry tactic to improve target selectivity of thiazole derivatives?

• Randomly increasing molecular weight without rationale
• Systematic SAR exploration around key substituents at positions 2, 4 and 5
• Never changing substituents once a lead is found
• Replacing the thiazole with elemental sulfur

Correct Answer: Systematic SAR exploration around key substituents at positions 2, 4 and 5

Q47. Which property commonly measured during lead profiling provides early insight into a thiazole candidate’s permeability?

• Caco‑2 cell permeability assay
• Flame photometry only
• Simple taste test
• Paper solubility index

Correct Answer: Caco‑2 cell permeability assay

Q48. Which class of analytical method is most appropriate for quantifying thiazole derivatives in plasma samples during PK studies?

• LC‑MS/MS bioanalytical methods
• Thin‑layer chromatography only
• Simple visual inspection
• pH paper strips

Correct Answer: LC‑MS/MS bioanalytical methods

Q49. In medicinal chemistry, exchanging a thiazole for an oxazole changes which key feature?

• Replacement of sulfur with oxygen changes polarity, hydrogen‑bonding and electronic distribution
• No chemical or biological property is affected
• It makes the compound metallic
• It converts the molecule into a peptide

Correct Answer: Replacement of sulfur with oxygen changes polarity, hydrogen‑bonding and electronic distribution

Q50. Which preclinical assay is essential to rule out major cardiac liability for a thiazole drug candidate before first‑in‑human studies?

• hERG channel inhibition assay (electrophysiology) and in vitro cardiac safety battery
• Only a taste and smell panel
• Paper chromatography for purity only
• Measuring optical rotation only

Correct Answer: hERG channel inhibition assay (electrophysiology) and in vitro cardiac safety battery

Download