Structure and uses of anthracene MCQs With Answer

Structure and uses of anthracene MCQs With Answer

Anthracene is a polycyclic aromatic hydrocarbon with three linearly fused benzene rings; understanding its structure, reactivity, spectroscopy, and pharmaceutical relevance is essential for B. Pharm students studying pharmaceutical chemistry and drug design. This topic covers aromaticity, resonance stabilization, preferred reaction sites (9,10-positions), photochemical behavior, oxidation to anthraquinone, and analytical methods like UV-Vis and NMR. Applications include fluorescent probes, organic electronics, intermediates in synthesis, and environmental/toxicological considerations. Mastery of these concepts helps with formulation, analysis, and safety assessment of anthracene derivatives in drug research. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which description best defines the molecular structure of anthracene?

• Three benzene rings fused linearly
• Three benzene rings fused angularly
• A single benzene ring with three substituents
• Two benzene rings connected by an aliphatic chain

Correct Answer: Three benzene rings fused linearly

Q2. Anthracene is classified as which type of organic compound?

• Alkane
• Polycyclic aromatic hydrocarbon (PAH)
• Aromatic heterocycle
• Alkene

Correct Answer: Polycyclic aromatic hydrocarbon (PAH)

Q3. In anthracene, which ring is most reactive toward electrophilic addition and Diels–Alder reactions?

• Terminal rings (outer rings)
• Central ring (9,10 positions)
• All rings are equally reactive
• None; anthracene is unreactive

Correct Answer: Central ring (9,10 positions)

Q4. Which resonance description explains anthracene’s aromatic stabilization?

• Delocalization across all three rings with dominant resonance in terminal rings
• Localized single benzene ring with two non-aromatic rings
• No resonance; structure is purely localized double bonds
• Resonance only in the central ring

Correct Answer: Delocalization across all three rings with dominant resonance in terminal rings

Q5. Compared to benzene, the resonance energy per ring in anthracene is:

• Higher per ring
• Lower per ring
• Equal per ring
• Undefined

Correct Answer: Lower per ring

Q6. Anthracene undergoes photodimerization upon UV irradiation to form which product?

• Dianthracene (cyclobutane-linked dimer)
• Anthraquinone directly
• Polymeric carbon soot
• Anthracene oxide

Correct Answer: Dianthracene (cyclobutane-linked dimer)

Q7. Oxidation of anthracene commonly yields which compound at the 9,10-positions?

• Anthraquinone
• Phenanthrene
• Naphthalene
• Benzoic acid

Correct Answer: Anthraquinone

Q8. Which spectroscopic method is most useful for identifying the conjugated pi system of anthracene?

• Infrared (IR) spectroscopy
• UV-Visible (UV-Vis) spectroscopy
• Polarimetry
• Flame photometry

Correct Answer: UV-Visible (UV-Vis) spectroscopy

Q9. Anthracene displays which photophysical property relevant for fluorescent probes?

• Strong blue fluorescence
• Weak non-radiative decay only
• Strong phosphorescence at room temperature
• No emission; only absorption

Correct Answer: Strong blue fluorescence

Q10. Which solvent property best describes anthracene solubility?

• Highly soluble in water
• Soluble mainly in nonpolar organic solvents
• Soluble in polar protic solvents only
• Soluble in concentrated acids only

Correct Answer: Soluble mainly in nonpolar organic solvents

Q11. In NMR spectroscopy, which protons of anthracene are typically most downfield (deshielded)?

• Protons on terminal rings at 1-position
• Protons at 9,10 positions (if present)
• All protons resonate at identical chemical shifts
• Protons on aliphatic substituents

Correct Answer: Protons at 9,10 positions (if present)

Q12. Which reaction type is especially favored at the 9,10-positions of anthracene?

• Nucleophilic aromatic substitution
• Diels–Alder cycloaddition
• Free radical halogenation at aliphatic positions
• Ozonolysis of isolated double bonds

Correct Answer: Diels–Alder cycloaddition

Q13. Which molecular orbital feature explains anthracene’s photochemistry?

• Large HOMO–LUMO gap with no π→π* transitions
• Accessible π→π* transitions enabling excited-state reactions
• Only σ→σ* transitions are possible
• No accessible excited states under UV light

Correct Answer: Accessible π→π* transitions enabling excited-state reactions

Q14. Which analytical technique is most appropriate for confirming anthracene’s molecular weight and fragmentation pattern?

• GC with thermal conductivity detector
• Mass spectrometry (MS)
• Infrared reflection spectroscopy
• Refractometry

Correct Answer: Mass spectrometry (MS)

Q15. Comparing anthracene and phenanthrene, which statement is true about their aromatic stabilization?

• Anthracene is more stabilized overall than phenanthrene
• Phenanthrene has greater resonance stabilization than anthracene
• Both have identical stabilization energies
• Neither exhibits resonance stabilization

Correct Answer: Phenanthrene has greater resonance stabilization than anthracene

Q16. Which is a common industrial use of anthracene or its derivatives?

• Fuel additive to increase octane number
• Intermediate in dye and pigment synthesis
• Primary solvent for injectable drugs
• Active pharmaceutical ingredient without modification

Correct Answer: Intermediate in dye and pigment synthesis

Q17. Anthracene’s environmental concern is mainly due to which property?

• High aqueous solubility leading to water contamination
• Being a polycyclic aromatic hydrocarbon with potential toxicity and persistence
• Volatility causing immediate air dissolution only
• Rapid biodegradation producing toxic metabolites

Correct Answer: Being a polycyclic aromatic hydrocarbon with potential toxicity and persistence

Q18. Which functionalization strategy is commonly used to increase anthracene’s water solubility for biological applications?

• Introduction of long alkyl chains
• Attachment of charged or polar groups (e.g., sulfonate, carboxylate)
• Hydrogenation to form alkanes
• Conversion to elemental carbon

Correct Answer: Attachment of charged or polar groups (e.g., sulfonate, carboxylate)

Q19. In pharmaceutical analysis, fluorescent anthracene derivatives are often used as:

• Non-fluorescent impurities
• Fluorescent probes or labels for bioassays
• Primary preservatives in formulations
• Buffering agents in tablets

Correct Answer: Fluorescent probes or labels for bioassays

Q20. Which safety precaution is most relevant when handling anthracene in the lab?

• No precautions needed; it is completely non-toxic
• Use of gloves and fume hood due to possible irritation and PAH concerns
• Store under strong reducing agents only
• Handle exclusively at cryogenic temperatures

Correct Answer: Use of gloves and fume hood due to possible irritation and PAH concerns

Q21. A key difference between electrophilic substitution on benzene vs. anthracene is:

• Anthracene only undergoes nucleophilic substitution
• Electrophiles preferentially attack the 9,10-positions in anthracene over terminal positions
• Benzene reacts at multiple positions while anthracene does not react
• Both react identically with no regioselectivity

Correct Answer: Electrophiles preferentially attack the 9,10-positions in anthracene over terminal positions

Q22. Anthracene derivatives used in organic electronics exploit which property?

• High ionic conductivity
• Conjugated pi system enabling charge transport
• Strong acidity
• Ability to chelate metal ions

Correct Answer: Conjugated pi system enabling charge transport

Q23. Which reaction converts anthracene to 9,10-dihydroanthracene?

• Hydrogenation of the central ring
• Oxidation with chromic acid
• Nitration under strong acid
• Photodimerization

Correct Answer: Hydrogenation of the central ring

Q24. In mass spectrometry, anthracene fragmentation often produces which stable fragment?

• CH4 radical
• Loss of C2H2 or formation of phenyl cations
• Complete molecular ion only with no fragments
• Pure oxygen-containing ions

Correct Answer: Loss of C2H2 or formation of phenyl cations

Q25. Which IR absorption would you expect to be weak or absent in pure anthracene?

• Strong O–H stretching bands
• Aromatic C–H stretching
• C=C aromatic stretches
• Out-of-plane C–H bending modes

Correct Answer: Strong O–H stretching bands

Q26. Anthracene’s central ring behaves like a diene in which type of reaction?

• Friedel–Crafts alkylation
• Diels–Alder reaction with suitable dienophiles
• Nucleophilic addition under basic conditions
• Radical polymerization with peroxides

Correct Answer: Diels–Alder reaction with suitable dienophiles

Q27. Which derivative of anthracene is common as a dye intermediate and oxidized product?

• Anisole
• Anthraquinone
• Chlorobenzene
• Benzylic alcohol

Correct Answer: Anthraquinone

Q28. Which statement about anthracene’s aromaticity in the ground state is correct?

• All three rings are equally aromatic like separate benzenes
• The molecule displays overall aromatic stabilization but resonance is concentrated in terminal rings in some forms
• Anthracene is antiaromatic
• It lacks any aromatic character

Correct Answer: The molecule displays overall aromatic stabilization but resonance is concentrated in terminal rings in some forms

Q29. Which laboratory method can separate anthracene from mixtures based on polarity?

• Reversed-phase HPLC tuned for nonpolar molecules
• Distillation using high polarity solvents only
• Ion-exchange chromatography
• Gel electrophoresis

Correct Answer: Reversed-phase HPLC tuned for nonpolar molecules

Q30. Photochemical excitation of anthracene typically leads to which excited-state species important in photochemistry?

• Only ground-state radicals
• Singlet and triplet excited states (S1 and T1)
• Excited ionic salts in solution
• Only vibrationally excited ground state

Correct Answer: Singlet and triplet excited states (S1 and T1)

Q31. In designing anthracene-based fluorescent probes for biological systems, a major concern is:

• Excessive water solubility causing rapid clearance
• Photostability and potential phototoxicity
• Inability to fluoresce in organic solvents
• Lack of any conjugated system

Correct Answer: Photostability and potential phototoxicity

Q32. Which substitution pattern on anthracene tends to block photodimerization?

• Bulky substituents at 9,10 positions
• Small hydrogen atoms at all positions
• Substitution at para positions only
• Complete hydrogenation of all rings

Correct Answer: Bulky substituents at 9,10 positions

Q33. Anthracene derivatives can serve as molecular scaffolds in drug discovery because of:

• High water solubility and ionic character
• Rigid planar aromatic framework amenable to functionalization
• Complete metabolic inertness in vivo
• Intrinsic enzyme inhibitory activity without modification

Correct Answer: Rigid planar aromatic framework amenable to functionalization

Q34. Which reagent is commonly used for electrophilic nitration of anthracene under controlled conditions?

• Nitric acid with sulfuric acid (mixed acid)
• Sodium borohydride
• Hydrogen peroxide alone
• Organolithium reagents at room temperature

Correct Answer: Nitric acid with sulfuric acid (mixed acid)

Q35. In UV-Vis spectra, anthracene’s prominent absorption is due to which transition?

• n→σ* transition
• π→π* transition of the conjugated system
• σ→σ* transition only
• Metal-to-ligand charge transfer

Correct Answer: π→π* transition of the conjugated system

Q36. Which biodegradation pathway is relevant for anthracene in the environment?

• Rapid hydrolysis to simple sugars
• Microbial dioxygenation leading to ring cleavage
• Spontaneous conversion to benzene under sunlight
• Conversion to elemental sulfur

Correct Answer: Microbial dioxygenation leading to ring cleavage

Q37. Which modification of anthracene can increase its suitability as an organic semiconductor?

• Adding polar ionic groups to increase solubility in water
• Introducing electron-donating or -withdrawing substituents to tune HOMO/LUMO
• Converting to a saturated hydrocarbon
• Adding heavy metals directly to the aromatic core

Correct Answer: Introducing electron-donating or -withdrawing substituents to tune HOMO/LUMO

Q38. Which property of anthracene is exploited in thin-film organic electronic devices?

• High thermal instability
• Planar conjugated structure facilitating π–π stacking
• Strong acidity for proton conduction
• High electrical conductivity as a metal

Correct Answer: Planar conjugated structure facilitating π–π stacking

Q39. Which safety classification commonly applies to polycyclic aromatic hydrocarbons like anthracene?

• Non-hazardous food additive
• Potential carcinogens or toxic environmental pollutants
• Explosive compounds
• Strong oxidizing agents

Correct Answer: Potential carcinogens or toxic environmental pollutants

Q40. In a synthesis route, converting anthracene to 9,10-epoxyanthracene involves which type of reagent?

• Peracid (e.g., mCPBA) for epoxidation
• Strong base for elimination reactions
• Hydrogen gas with palladium catalyst only
• Dry HCl gas

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

Q41. When analyzing anthracene derivatives by HPLC, detection by fluorescence is advantageous because:

• Anthracene derivatives are generally non-fluorescent
• Fluorescence offers high sensitivity and selectivity for conjugated aromatics
• Fluorescence detectors are insensitive to PAHs
• Anthracene quenches all fluorescence detectors

Correct Answer: Fluorescence offers high sensitivity and selectivity for conjugated aromatics

Q42. Which molecular change reduces anthracene’s aromatic character significantly?

• Attachment of small methyl groups at peripheral positions
• Hydrogenation of the central ring to form dihydro derivatives
• Substitution with nitro groups at remote positions only
• Formation of salts with strong bases

Correct Answer: Hydrogenation of the central ring to form dihydro derivatives

Q43. Anthracene’s ability to form charge-transfer complexes is due to:

• Its saturated aliphatic backbone
• Electron-rich conjugated pi system
• Presence of metal centers
• High ionic charge in the neutral molecule

Correct Answer: Electron-rich conjugated pi system

Q44. Which pharmaceutical formulation challenge is associated with anthracene-based compounds?

• Excessive hydrophilicity causing gelation
• Poor aqueous solubility requiring suitable solubilizers or delivery systems
• Inability to be formulated into solid dosage forms
• Extreme volatility at room temperature

Correct Answer: Poor aqueous solubility requiring suitable solubilizers or delivery systems

Q45. Which reaction can convert anthracene into a more polar, water-soluble product suitable for biological assays?

• Alkylation with long nonpolar chains
• Sulfonation or carboxylation to introduce polar groups
• Hydrogenation to produce saturated hydrocarbons
• Metal deposition onto the aromatic surface

Correct Answer: Sulfonation or carboxylation to introduce polar groups

Q46. In electronic spectroscopy, an increase in conjugation in anthracene derivatives typically causes:

• Hypsochromic (blue) shift in absorption
• Bathochromic (red) shift in absorption
• No change in absorption wavelength
• Disappearance of all absorption bands

Correct Answer: Bathochromic (red) shift in absorption

Q47. Which method is effective to prevent photodimerization of anthracene during storage?

• Store under strong UV light
• Keep in the dark or add stabilizers and store at low temperature
• Expose to ozone periodically
• Store in concentrated acid

Correct Answer: Keep in the dark or add stabilizers and store at low temperature

Q48. Anthracene’s central 9,10-positions are often targeted in synthesis because:

• They are sterically inaccessible and inert
• They offer higher reactivity due to resonance stabilization of intermediates
• They cannot form covalent bonds
• They are the only positions that are aromatic

Correct Answer: They offer higher reactivity due to resonance stabilization of intermediates

Q49. Which biological concern is associated with exposure to anthracene and related PAHs?

• Complete nutritional benefits at low doses
• Potential mutagenic and carcinogenic effects with chronic exposure
• Guaranteed antimicrobial action in humans
• No biological interaction due to inertness

Correct Answer: Potential mutagenic and carcinogenic effects with chronic exposure

Q50. For a B. Pharm student, mastering anthracene chemistry helps primarily in understanding:

• Only clinical trial design unrelated to chemistry
• Structure–reactivity relationships, photochemistry, analysis, and implications for drug design and safety
• How to manufacture inorganic salts
• Only pharmacy law and regulations

Correct Answer: Structure–reactivity relationships, photochemistry, analysis, and implications for drug design and safety

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com