Reactions of acridine MCQs With Answer

Reactions of acridine MCQs With Answer

Understanding reactions of acridine is essential for B. Pharm students studying pharmaceutical chemistry and drug design. Acridine and its derivatives undergo characteristic electrophilic substitution at the 9-position, N‑alkylation to form acridinium salts, reductions to leucoacridines, and nucleophilic addition reactions; these transformations influence biological activity and photophysical behavior. Mastery of mechanisms, regiochemistry, common reagents, and spectral features helps predict synthetic routes and anticipate drug interactions. This targeted practice emphasizes reagent selection, mechanism understanding, regioselectivity, and pharmaceutical implications to prepare for university exams and competitive assessments. Each MCQ includes answers and brief explanation cues to aid revision. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which position on the acridine nucleus is most susceptible to electrophilic substitution?

• 1-position (peripheral ring)
• 2-position (peripheral ring)
• 9-position (central carbon)
• N-position (nitrogen atom)

Correct Answer: 9-position (central carbon)

Q2. N‑alkylation of acridine typically yields which class of compounds important in photochemistry?

• Acridones
• Acridinium salts
• Acridanes
• Acridinesulfonates

Correct Answer: Acridinium salts

Q3. Reduction of acridine often gives which hydrogenated product?

• Acridinium ion
• 9,10-Dihydroacridine (leucoacridine)
• Acridone
• Acridine N-oxide

Correct Answer: 9,10-Dihydroacridine (leucoacridine)

Q4. Which reagent is commonly used for quaternization (N‑alkylation) of acridine?

• Alkyl bromide (e.g., methyl bromide)
• Sodium borohydride
• Chromic acid
• Nitric acid

Correct Answer: Alkyl bromide (e.g., methyl bromide)

Q5. Acridinium salts are widely used as which type of catalysts in modern organic synthesis?

• Lewis acid catalysts
• Photoredox catalysts
• Base catalysts
• Metal hydride catalysts

Correct Answer: Photoredox catalysts

Q6. Which transformation converts acridine into an electrically positive species useful in electron-transfer reactions?

• Nitration
• Oxidation to acridinium cation
• Reduction to leucoacridine
• Sulfonation

Correct Answer: Oxidation to acridinium cation

Q7. The planar polyaromatic structure of acridine enables which biologically relevant interaction?

• Alkylation of proteins
• DNA intercalation
• Covalent binding to receptors
• Metal chelation

Correct Answer: DNA intercalation

Q8. Electrophilic aromatic substitution of acridine proceeds most readily on which ring type?

• Peripheral benzene rings similar to benzene
• Central ring carbons (9-position)
• Nitrogen-containing ring positions
• Exocyclic double bonds

Correct Answer: Central ring carbons (9-position)

Q9. Nucleophilic addition to acridine under acidic conditions typically targets which site?

• Nitrogen lone pair
• 9-position (carbon electrophile)
• Peripheral aromatic carbons
• Hydrogen atoms

Correct Answer: 9-position (carbon electrophile)

Q10. The leucoacridine form is best described as:

• A fully aromatic acridinium ion
• A reduced, non-aromatic or partially saturated derivative
• An oxidized radical cation
• A sulfonated derivative

Correct Answer: A reduced, non-aromatic or partially saturated derivative

Q11. Which analytical technique is most informative for identifying substitution at the 9-position of acridine?

• Infrared spectroscopy only
• 1H NMR and 13C NMR
• Thin layer chromatography only
• Melting point analysis only

Correct Answer: 1H NMR and 13C NMR

Q12. Sulfonation of acridine typically introduces which functional group?

• –NO2 (nitro)
• –SO3H (sulfonic acid)
• –OH (hydroxyl)
• –Cl (chloro)

Correct Answer: –SO3H (sulfonic acid)

Q13. Which one of the following is a common use of acridine derivatives in pharmaceuticals?

• Antibacterial DNA-intercalating agents
• Enzyme prosthetic groups
• Protein structural components
• Dietary supplements

Correct Answer: Antibacterial DNA-intercalating agents

Q14. Formation of acridine N‑oxide is usually achieved by reaction with which reagent?

• Sodium borohydride
• Peracid (e.g., mCPBA)
• Alkyl halide
• Hydrochloric acid

Correct Answer: Peracid (e.g., mCPBA)

Q15. Oxidation of leucoacridine regenerates which species?

• Acridine
• Acridinium salt
• Acridone
• Acridine hydride

Correct Answer: Acridine

Q16. In synthesis, electrophilic halogenation of acridine commonly yields substitution at:

• N-position
• 9-position or adjacent activated positions
• Unactivated peripheral carbons randomly
• Only the 3-position

Correct Answer: 9-position or adjacent activated positions

Q17. Which property of acridinium salts makes them useful as fluorescent probes?

• High melting point
• Strong visible absorption and emissive excited states
• Insolubility in organic solvents
• Rigid nonplanar geometry

Correct Answer: Strong visible absorption and emissive excited states

Q18. Which reaction type is least characteristic for acridine chemistry?

• Electrophilic aromatic substitution
• N‑alkylation to give acridinium salts
• Simple nucleophilic aromatic substitution on unsubstituted peripheral rings
• Reduction to dihydro derivatives

Correct Answer: Simple nucleophilic aromatic substitution on unsubstituted peripheral rings

Q19. Photochemical reactions of acridines often involve:

• Photoinduced electron transfer
• Formation of stable carbocations without light
• Spontaneous polymerization in the dark
• Metal insertion

Correct Answer: Photoinduced electron transfer

Q20. Mannich-type reactions on acridine usually require which functional group present on the substrate?

• Activated hydrogen at the 9-position
• Strong electron-withdrawing nitro group only
• Carboxylic acid at N-position
• Metal-binding thiol

Correct Answer: Activated hydrogen at the 9-position

Q21. Which statement about acridine basicity is correct?

• Acridine nitrogen is as basic as aliphatic amines
• Acridine nitrogen is weakly basic due to aromatic delocalization
• Acridine is a strong base with pKa > 12
• Acridine cannot be protonated

Correct Answer: Acridine nitrogen is weakly basic due to aromatic delocalization

Q22. Which derivative results from oxidative cleavage of acridine under severe conditions?

• Acridinium ion
• Ring-opened carbonyl compounds
• Leucoacridine
• N‑alkylacridine

Correct Answer: Ring-opened carbonyl compounds

Q23. The term “leuco” in leucoacridine refers to:

• Oxidized colored form
• Reduced colorless or pale form
• Highly fluorescent derivative
• Sulfonated derivative

Correct Answer: Reduced colorless or pale form

Q24. Electrophilic nitration of acridine preferentially gives nitro substitution at:

• Random peripheral positions
• Positions activated by resonance, often near the 9-position
• N‑atom
• Only the 3-position exclusively

Correct Answer: Positions activated by resonance, often near the 9-position

Q25. Which synthetic route is commonly used to prepare acridines from diarylamines?

• Friedel–Crafts acylation followed by cyclization
• Buchwald–Hartwig amination only
• Diels–Alder reaction exclusively
• Hydrolysis of esters

Correct Answer: Friedel–Crafts acylation followed by cyclization

Q26. Which of the following is a typical reagent for reducing acridine to leucoacridine in the lab?

• Chromium trioxide
• Sodium borohydride or catalytic hydrogenation
• Nitric acid
• Peracetic acid

Correct Answer: Sodium borohydride or catalytic hydrogenation

Q27. Acridinium salts are stabilized by which feature?

• Delocalization of the positive charge over the aromatic system
• Localized charge at nitrogen only
• Strong hydrogen bonding to water
• Coordination to transition metals

Correct Answer: Delocalization of the positive charge over the aromatic system

Q28. Which spectroscopic change indicates conversion of acridine to its acridinium form?

• Loss of all UV-visible absorption
• Appearance of new strong visible absorption bands and often enhanced fluorescence
• Only infrared bands change
• No change in spectra

Correct Answer: Appearance of new strong visible absorption bands and often enhanced fluorescence

Q29. Which substituent strongly directs electrophiles to the 9-position of acridine?

• Strong electron-withdrawing nitro group at remote position
• Electron-donating alkyl or amino substitution that increases electron density at 9-position
• Bulky tertiary butyl at the N-position
• Perfluoroalkyl substituent

Correct Answer: Electron-donating alkyl or amino substitution that increases electron density at 9-position

Q30. Which reaction can convert acridine into acridone (a carbonyl-containing derivative)?

• N‑alkylation with alkyl halides
• Oxidation followed by rearrangement to introduce a carbonyl
• Simple dehydrogenation only
• Photoreduction

Correct Answer: Oxidation followed by rearrangement to introduce a carbonyl

Q31. In medicinal chemistry, incorporation of an acridine moiety often increases:

• Hydrophilicity dramatically
• Planarity and potential for DNA intercalation
• Covalent irreversible enzyme inhibition only
• Non-specific protein aggregation exclusively

Correct Answer: Planarity and potential for DNA intercalation

Q32. Which of the following is a common side reaction during electrophilic substitution of acridine?

• Uncontrolled oxidation of the aromatic system
• Immediate polymerization to insoluble polymers
• Cleavage of the nitrogen atom
• Formation of stable metal complexes

Correct Answer: Uncontrolled oxidation of the aromatic system

Q33. Which reagent pair would best effect electrophilic bromination of the acridine ring?

• HBr and H2O
• Br2 with a Lewis acid or FeBr3
• NaBr in water only
• Sodium azide and heat

Correct Answer: Br2 with a Lewis acid or FeBr3

Q34. Acridine derivatives showing reversible redox behavior in cyclic voltammetry are often useful in:

• Hydrogen storage
• Electron-transfer studies and photoredox catalysis
• Protein folding assays
• Bulk explosives

Correct Answer: Electron-transfer studies and photoredox catalysis

Q35. Which of the following best explains why acridine intercalates DNA?

• Strong ionic charge only
• Planar aromatic surface that stacks with base pairs
• Specific covalent bond formation with sugar moiety
• Hydrophobic pocket formation in aqueous buffer

Correct Answer: Planar aromatic surface that stacks with base pairs

Q36. When comparing acridine and acridinium cations, acridinium salts are generally:

• Less electrophilic than acridine
• More electrophilic and better photooxidants
• Completely inert
• Impossible to synthesize

Correct Answer: More electrophilic and better photooxidants

Q37. Which substituent would most decrease the nucleophilicity of the acridine nitrogen?

• Methyl group at nitrogen
• N-oxide formation
• Electron-withdrawing substituent on ring
• Hydrogen at nitrogen

Correct Answer: Electron-withdrawing substituent on ring

Q38. In synthetic schemes, protecting acridine nitrogen from alkylation might involve:

• Temporary protonation to block nucleophilicity
• Using excess alkyl halide
• Oxidation to acridinium first
• Adding strong base to deprotonate

Correct Answer: Temporary protonation to block nucleophilicity

Q39. Which structural change typically increases water solubility of acridine derivatives for pharmaceutical use?

• Introduction of lipophilic alkyl chains
• Quaternization of nitrogen or introduction of polar groups
• Removal of heteroatoms
• Increasing planarity only

Correct Answer: Quaternization of nitrogen or introduction of polar groups

Q40. Which mechanism best describes nucleophilic addition to the 9-position of acridine?

• Electrophilic aromatic substitution
• Conjugate (1,4) addition only
• Nucleophilic addition to an electron-deficient carbon followed by proton transfer
• Free radical substitution exclusively

Correct Answer: Nucleophilic addition to an electron-deficient carbon followed by proton transfer

Q41. Which functionalization method is commonly used to introduce amino groups on acridine rings?

• Nitration followed by reduction
• Direct amination without activation in all cases
• Hydrogenation only
• Saponification

Correct Answer: Nitration followed by reduction

Q42. Which of these is a risk when designing acridine-based drugs?

• Excessive water solubility
• Potential genotoxicity due to DNA intercalation
• Inability to cross membranes because of extreme reactivity
• Complete metabolic stability with no clearance

Correct Answer: Potential genotoxicity due to DNA intercalation

Q43. Which reaction can convert acridine into a more polar, excretable metabolite in the body?

• Phase II conjugation such as glucuronidation of hydroxylated derivatives
• Spontaneous polymerization
• Formation of stable acridinium salts only
• Complete conversion to elemental carbon

Correct Answer: Phase II conjugation such as glucuronidation of hydroxylated derivatives

Q44. Which modification often reduces DNA intercalation while retaining other pharmacophores?

• Increasing planarity further
• Adding bulky substituents that disrupt planar stacking
• Quaternization to make a strong intercalator
• Removing polar groups

Correct Answer: Adding bulky substituents that disrupt planar stacking

Q45. Which oxidation state change is involved when acridine is converted to an acridinium radical cation under photochemical conditions?

• Reduction by one electron
• Oxidation by one electron (loss of electron)
• No change in electron count
• Complete cleavage of the aromatic system

Correct Answer: Oxidation by one electron (loss of electron)

Q46. Which heteroatom modification is commonly explored to tune acridine electronic properties?

• Replacing carbon atoms with silicon only
• Introduction of substituents (electron-donating or withdrawing) on rings or N-alkylation
• Removing the nitrogen entirely without replacement
• Adding heavy metals into the ring

Correct Answer: Introduction of substituents (electron-donating or withdrawing) on rings or N-alkylation

Q47. Which type of catalysts can facilitate cross-coupling to functionalize acridine rings?

• Acid catalysts only
• Palladium or copper catalysts (e.g., Suzuki, Buchwald conditions)
• Photocatalysts only
• Enzymes only

Correct Answer: Palladium or copper catalysts (e.g., Suzuki, Buchwald conditions)

Q48. In the context of B. Pharm exams, mastering acridine reactions helps primarily in understanding:

• Formulation rheology
• Drug–DNA interactions, synthetic modifications, and photochemical behavior
• Opthalmic device design
• Tablet coating mechanics only

Correct Answer: Drug–DNA interactions, synthetic modifications, and photochemical behavior

Q49. Which reaction condition favors formation of 9-substituted acridine derivatives?

• Strongly basic nucleophilic conditions only
• Electrophilic reagents or activated intermediates targeting the 9-position
• High dilution with no reagents
• Photolysis without sensitizer always

Correct Answer: Electrophilic reagents or activated intermediates targeting the 9-position

Q50. For safe laboratory handling, which precaution is especially relevant for acridine derivatives?

• No precautions needed; they are non-toxic
• Use of gloves and fume hood because of potential mutagenicity and dust inhalation
• Storage in open containers at high temperature
• Direct disposal down the sink without neutralization

Correct Answer: Use of gloves and fume hood because of potential mutagenicity and dust inhalation

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