Synthesis of furan MCQs With Answer

Synthesis of furan MCQs With Answer — This concise, SEO-friendly introduction covers key routes, reagents and mechanisms involved in the synthesis of furan rings relevant to B.Pharm students. Topics include Paal–Knorr and Feist–Bénary approaches, biomass-derived routes via furfural and hydroxymethylfurfural (HMF), catalytic methods, regioselectivity in electrophilic substitution, aromaticity and spectroscopic identification. Emphasis is on reaction conditions, common intermediates, safety and pharmaceutical relevance of furan-containing compounds. These MCQs will help you master synthetic strategies, reaction mechanisms and practical considerations for heterocyclic furan chemistry important in drug design and process chemistry. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the classical Paal–Knorr synthesis precursor for preparing substituted furans?

• 1,3-diketone
• 1,4-diketone
• α,β‑unsaturated carbonyl
• 1,2-diol

Correct Answer: 1,4-diketone

Q2. Which condition most commonly promotes Paal–Knorr furan formation from 1,4-diketones?

• Strong base and low temperature
• Acid catalysis or heat
• Radical initiator with peroxide
• Neutral aqueous conditions

Correct Answer: Acid catalysis or heat

Q3. The Feist–Bénary furan synthesis typically involves which pair of reactants?

• α-haloketone and β-dicarbonyl compound
• Alkyne and diazo compound
• Vinyl halide and Grignard reagent
• Primary alcohol and aldehyde

Correct Answer: α-haloketone and β-dicarbonyl compound

Q4. Furfural is primarily obtained from which biomass feedstock?

• Lignin
• Cellulose directly
• Hemicellulose (pentosans)
• Triglycerides

Correct Answer: Hemicellulose (pentosans)

Q5. Hydroxymethylfurfural (HMF) is an important intermediate derived from:

• Amino acids by decarboxylation
• Dehydration of hexose sugars
• Oxidation of furfuryl alcohol
• Hydrogenation of furfural

Correct Answer: Dehydration of hexose sugars

Q6. Which statement correctly describes the aromaticity of furan?

• Furan is non-aromatic due to sp3 oxygen
• Furan is antiaromatic with 4π electrons
• Furan is aromatic with a 6π electron system including one lone pair
• Furan’s aromaticity is identical to benzene

Correct Answer: Furan is aromatic with a 6π electron system including one lone pair

Q7. In electrophilic aromatic substitution of furan, substitution preferentially occurs at which position?

• Position 3
• Position 2
• Position 4
• Position 5 only under radical conditions

Correct Answer: Position 2

Q8. Which reagent is commonly used to reduce furfural to furfuryl alcohol?

• Lithium diisobutylaluminum hydride (LDBA)
• Sodium borohydride (NaBH4)
• Chromic acid
• Ozone

Correct Answer: Sodium borohydride (NaBH4)

Q9. Oxidation of furan rings with strong oxidants often produces:

• Benzoic acid
• Maleic anhydride
• Furanone exclusively
• Phenol derivatives

Correct Answer: Maleic anhydride

Q10. Which transformation converts furfuryl alcohol into useful pyranone intermediates used in synthesis?

• Aldol condensation
• Achmatowicz rearrangement
• Sandmeyer reaction
• Buchwald–Hartwig amination

Correct Answer: Achmatowicz rearrangement

Q11. Furan behaves as a diene in Diels–Alder reactions; the adduct is typically:

• Very stable at high temperatures
• Reversible and can undergo retro-Diels–Alder on heating
• Unreactive due to aromatic stabilization
• Only formed under radical conditions

Correct Answer: Reversible and can undergo retro-Diels–Alder on heating

Q12. Which spectroscopic signal range is typical for furan proton resonances in 1H NMR?

• 0.5–1.5 ppm
• 2.0–3.0 ppm
• 6.0–7.5 ppm
• 9.0–10.5 ppm

Correct Answer: 6.0–7.5 ppm

Q13. Which statement about furan reactivity under acidic conditions is correct?

• Furan is completely inert to acids
• Acids can cause polymerization or ring opening
• Acidic conditions always give higher yields of furans
• Acids convert furan to benzofuran directly

Correct Answer: Acids can cause polymerization or ring opening

Q14. The Paal–Knorr reaction mechanism involves initial:

• Nucleophilic aromatic substitution
• Intramolecular cyclization via enolization
• Free radical addition to the diketone
• Pericyclic electrocyclization

Correct Answer: Intramolecular cyclization via enolization

Q15. In Feist–Bénary synthesis, the formation of furan often proceeds through which intermediate?

• Oxirane
• Enolate addition followed by elimination to form furan
• Carbene insertion into C–H bond
• Nitrone intermediate

Correct Answer: Enolate addition followed by elimination to form furan

Q16. Which catalyst class is frequently used to promote biomass-derived furfural conversion to value-added furans?

• Organometallic palladium catalysts only
• Acidic solid catalysts (e.g., sulfonated resins)
• Pure bases like sodium hydroxide
• Enzymes only

Correct Answer: Acidic solid catalysts (e.g., sulfonated resins)

Q17. Which reagent is commonly used to oxidize furfuryl alcohol to furfural in laboratory practice?

• PCC (pyridinium chlorochromate)
• NaBH4
• LiAlH4
• Hydrazine

Correct Answer: PCC (pyridinium chlorochromate)

Q18. What is a significant safety concern associated with furan as a solvent or reagent in pharmaceutical labs?

• Strongly basic and corrosive
• Highly allergenic but non-toxic
• Hepatotoxic and possibly carcinogenic
• Non-flammable and inert

Correct Answer: Hepatotoxic and possibly carcinogenic

Q19. Which of the following best describes the electronic character of furan compared with benzene?

• Furan is more electron-deficient than benzene
• Furan is more electron-rich due to oxygen lone pair donation
• Furan and benzene have identical electron densities
• Furan is completely non-aromatic

Correct Answer: Furan is more electron-rich due to oxygen lone pair donation

Q20. Which functional group transformation is most useful to introduce substituents at C-2 of furan selectively?

• Direct lithiation at C-2 followed by electrophile quench
• Oxidation of furan to benzofuran
• Nitration followed by reduction
• Hydrogenation then functionalization

Correct Answer: Direct lithiation at C-2 followed by electrophile quench

Q21. Which reagent combination is typical for halogenation of furan at the 2-position under mild conditions?

• NBS in the presence of a radical initiator
• Br2 in acetic acid under cold conditions
• SOCl2 with catalytic DMF
• NaBr in water

Correct Answer: Br2 in acetic acid under cold conditions

Q22. The conversion of 1,4-dicarbonyl compounds to furans is driven thermodynamically by:

• Formation of a strained four-membered ring
• Loss of aromaticity
• Gain of aromatic stabilization in the furan ring
• Formation of stable free radicals

Correct Answer: Gain of aromatic stabilization in the furan ring

Q23. In synthetic planning, furan rings are often used as:

• Inert spacers that never react further
• Electron-poor heterocycles for nucleophilic aromatic substitution
• Versatile electron-rich building blocks for further functionalization
• Metal-binding ligands exclusively

Correct Answer: Versatile electron-rich building blocks for further functionalization

Q24. Which protecting strategy is commonly used to prevent furan polymerization during storage or reaction?

• Convert to the corresponding furan oxide
• Store under inert atmosphere and low temperature with antioxidant
• Add strong acid stabilizer
• Expose to UV light to form stable photoproducts

Correct Answer: Store under inert atmosphere and low temperature with antioxidant

Q25. Which product results from the catalytic hydrogenation of furan under mild conditions?

• Tetrahydrofuran (THF)
• Furan oxide
• Furfural
• Maleic anhydride

Correct Answer: Tetrahydrofuran (THF)

Q26. Which spectroscopic feature helps distinguish furans from other five-membered heterocycles in IR?

• Strong carbonyl stretch at 1700 cm−1
• C–H stretching of aromatic ring at ~3100 cm−1 and C–O stretching around 1000–1300 cm−1
• N–H stretch at 3300 cm−1
• Absence of C–H stretches

Correct Answer: C–H stretching of aromatic ring at ~3100 cm−1 and C–O stretching around 1000–1300 cm−1

Q27. Which transformation is a common route to synthesize highly substituted furans in medicinal chemistry?

• Sequential cross-coupling on preformed furan core
• Direct electrophilic nitration only
• Thermal cracking of furan polymers
• Oxidative cleavage to form carboxylic acids

Correct Answer: Sequential cross-coupling on preformed furan core

Q28. In designing a synthesis to avoid over-oxidation of furan, which oxidant should be avoided?

• Mild TEMPO-based oxidants
• mCPBA under controlled conditions
• Strong permanganate or nitric acid
• PCC in dichloromethane at low temperature

Correct Answer: Strong permanganate or nitric acid

Q29. Which heterocycle is formed by annulation of furan with an additional aromatic ring under oxidative conditions?

• Thiophene
• Benzofuran
• Pyrrole
• Imidazole

Correct Answer: Benzofuran

Q30. Which factor often controls regioselectivity in electrophilic substitution of substituted furans?

• Steric hindrance and resonance stabilization of intermediates
• Only solvent polarity
• Magnetic field orientation
• Color of reaction mixture

Correct Answer: Steric hindrance and resonance stabilization of intermediates

Q31. Which step is essential when converting a carbohydrate to furfural on an industrial scale?

• Hydrogenation under high pressure
• Acid-catalyzed dehydration of pentoses
• Direct photolysis of cellulose
• Enzymatic decarboxylation

Correct Answer: Acid-catalyzed dehydration of pentoses

Q32. Which of the following is a common application of furan derivatives in pharmaceuticals?

• As inert fillers only
• Core scaffolds in antiviral and antibiotic agents
• Used exclusively as solvents
• Never used due to toxicity

Correct Answer: Core scaffolds in antiviral and antibiotic agents

Q33. A successful Paal–Knorr furan synthesis fails; likely cause could be:

• Using non-enolisable 1,4-diketone
• Excess base present in reaction mixture
• Absence of a radical initiator
• Presence of a strong oxidant

Correct Answer: Excess base present in reaction mixture

Q34. Which metal-catalyzed cross-coupling is widely used to functionalize halogenated furans?

• Wurtz coupling
• Pd-catalyzed Suzuki–Miyaura coupling
• Free-radical polymerization
• Michael addition only

Correct Answer: Pd-catalyzed Suzuki–Miyaura coupling

Q35. Which synthetic conversion converts furfural into useful furan-based monomers for polymer chemistry?

• Oxidation to CO2
• Reduction and subsequent functionalization to produce diols or vinyl derivatives
• Complete hydrogenolysis to methane
• Photocleavage to form benzene

Correct Answer: Reduction and subsequent functionalization to produce diols or vinyl derivatives

Q36. During furan synthesis, why is controlling moisture often important?

• Water increases aromaticity of furan
• Moisture can hydrolyze sensitive intermediates and reduce yields
• Water acts as a catalyst for Paal–Knorr always
• Moisture prevents catalyst poisoning always

Correct Answer: Moisture can hydrolyze sensitive intermediates and reduce yields

Q37. Which reagent is commonly used to transform a furan into a furanone via selective oxidation?

• Potassium permanganate under vigorous conditions
• DDQ or MnO2 under controlled conditions
• LiAlH4 reduction
• H2/Pd hydrogenation

Correct Answer: DDQ or MnO2 under controlled conditions

Q38. Which type of mechanism is typically involved when furans undergo electrophilic substitution?

• Free radical chain mechanism
• Formation of a resonance-stabilized carbocation (Wheland intermediate)
• Concerted pericyclic substitution
• Single electron transfer only

Correct Answer: Formation of a resonance-stabilized carbocation (Wheland intermediate)

Q39. In preparing substituted furans via enamine chemistry, the key step often is:

• Electrophilic addition to an olefin
• Condensation of an enamine with an acylating agent followed by cyclization
• SN2 displacement on saturated carbon
• Direct nitration of enamine

Correct Answer: Condensation of an enamine with an acylating agent followed by cyclization

Q40. Which property of furan explains its higher reactivity toward electrophiles compared to benzene?

• Higher bond dissociation energies
• Electron-donating oxygen lone pair increases electron density in the ring
• Lower HOMO energy
• Complete lack of resonance stabilization

Correct Answer: Electron-donating oxygen lone pair increases electron density in the ring

Q41. Which approach forms furans via intramolecular cyclization of 1,4-dicarbonyls under basic conditions?

• Paal–Knorr under strongly basic medium
• Knoevenagel condensation followed by cyclodehydration
• Birch reduction
• Fischer esterification

Correct Answer: Knoevenagel condensation followed by cyclodehydration

Q42. Which protecting group is compatible with furan chemistry during multi-step synthesis?

• Tert-butyldimethylsilyl (TBS) on adjacent alcohols to avoid acid sensitivity
• Acetal formation on furan ring itself
• Direct methylation of furan oxygen
• Forming epoxides on the ring

Correct Answer: Tert-butyldimethylsilyl (TBS) on adjacent alcohols to avoid acid sensitivity

Q43. Which reaction can convert a furan derivative to a carboxylic acid-substituted product?

• Oxidative ring opening with strong oxidants like KMnO4
• Hydrogenation to saturated ring only
• Reduction with NaBH4
• Friedel–Crafts acylation

Correct Answer: Oxidative ring opening with strong oxidants like KMnO4

Q44. Which synthetic strategy allows regioselective introduction of an aryl group at furan 5-position?

• Directed ortho metalation at 2-position only
• Palladium-catalyzed direct C–H arylation using appropriate directing effects
• Random halogenation followed by cross-coupling without selectivity
• Photochemical dimerization

Correct Answer: Palladium-catalyzed direct C–H arylation using appropriate directing effects

Q45. Which analytical technique is most definitive for confirming furan ring formation in a new compound?

• TLC alone
• Combination of 1H/13C NMR and mass spectrometry
• Only melting point measurement
• Color observation

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

Q46. During scale-up of furan synthesis, which concern is most critical to monitor?

• Color of final product only
• Thermal runaway due to exothermic steps and polymerization
• Noise levels in the plant
• Magnetic susceptibility

Correct Answer: Thermal runaway due to exothermic steps and polymerization

Q47. Which reagent set can be used to convert a 1,4-diketone to a furan via dehydrative cyclization under milder conditions?

• Strong base and peroxide
• Acidic catalysts like p-TsOH in toluene with Dean–Stark apparatus
• Radical initiator and UV light
• High pressure hydrogen without catalyst

Correct Answer: Acidic catalysts like p-TsOH in toluene with Dean–Stark apparatus

Q48. Which statement best reflects environmental considerations for furan production from biomass?

• Biomass routes are always non-green due to acid use
• Process optimization can minimize acid waste and use heterogeneous catalysts for greener conversion
• Furfural production cannot be improved technologically
• Only petrochemical routes are sustainable

Correct Answer: Process optimization can minimize acid waste and use heterogeneous catalysts for greener conversion

Q49. Which transformation converts furans into more stable aromatic benzene derivatives?

• Direct oxidation to benzene
• Diels–Alder with a dienophile followed by aromatization strategies to form substituted benzenes
• Simple aqueous hydrolysis
• Hydrogenolysis under mild conditions

Correct Answer: Diels–Alder with a dienophile followed by aromatization strategies to form substituted benzenes

Q50. For exam-focused synthesis questions, which concept is most important to demonstrate when proposing a furan synthesis route?

• Only list reagents without mechanism
• Show retrosynthetic thinking, key intermediates, reagents, conditions and brief mechanism rationale
• Provide unrelated literature references
• Focus solely on cost without chemistry

Correct Answer: Show retrosynthetic thinking, key intermediates, reagents, conditions and brief mechanism rationale

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.

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