Structure and uses of resorcinol MCQs With Answer

Introduction: Resorcinol, chemically known as 1,3-dihydroxybenzene, is a versatile phenolic compound with distinct structure and wide pharmaceutical relevance. B. Pharm students must understand its molecular structure, physicochemical properties, acidity (pKa), reactivity in electrophilic substitutions, and methods of synthesis and analysis. Resorcinol is used in topical antiseptics, keratolytic agents, and as a precursor for resorcinol-formaldehyde resins and dye intermediates. Knowledge of formulation compatibility, assay techniques (e.g., HPLC, ferric chloride test), and safety considerations is essential for safe handling and effective product design. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the IUPAC name of resorcinol?

• 1,2-dihydroxybenzene
• 1,3-dihydroxybenzene
• 1,4-dihydroxybenzene
• 3,4-dihydroxybenzene

Correct Answer: 1,3-dihydroxybenzene

Q2. What is the molecular formula of resorcinol?

• C6H6O2
• C7H8O2
• C6H4O2
• C6H5OH

Correct Answer: C6H6O2

Q3. Which functional groups are present in resorcinol?

• Two aldehyde groups
• Two hydroxyl groups attached to an aromatic ring
• One hydroxyl and one carboxyl group
• One amino and one hydroxyl group

Correct Answer: Two hydroxyl groups attached to an aromatic ring

Q4. Which positions do the two hydroxyl groups occupy on the benzene ring in resorcinol?

• Ortho (1,2-) positions
• Meta (1,3-) positions
• Para (1,4-) positions
• Geminal positions

Correct Answer: Meta (1,3-) positions

Q5. How is resorcinol usually described at room temperature?

• Colorless gas
• White crystalline solid
• Yellow oily liquid
• Colorless aqueous solution

Correct Answer: White crystalline solid

Q6. Which industrial route is commonly used to produce resorcinol?

• Oxidation of toluene directly to resorcinol
• Sulfonation of benzene followed by alkaline fusion
• Direct hydration of benzene to form dihydroxybenzene
• Reduction of phenol under high pressure

Correct Answer: Sulfonation of benzene followed by alkaline fusion

Q7. Resorcinol is classified as which type of aromatic compound?

• Phenol
• Aldehyde
• Carboxylic acid
• Amide

Correct Answer: Phenol

Q8. Which property of resorcinol explains its ability to form hydrogen bonds?

• Presence of aromatic ring
• Presence of hydroxyl groups
• High molecular weight
• Lack of heteroatoms

Correct Answer: Presence of hydroxyl groups

Q9. Relative to phenol, resorcinol’s acidity is:

• Much weaker
• Comparable to phenol
• Stronger due to electron-withdrawing groups
• Stronger due to intramolecular hydrogen bonding and resonance

Correct Answer: Comparable to phenol

Q10. The approximate pKa value often cited for resorcinol (first dissociation) is:

• ~4.2
• ~6.5
• ~9.3
• ~12.8

Correct Answer: ~9.3

Q11. Which color change is typically observed when resorcinol reacts with ferric chloride solution?

• No color change
• Green
• Violet
• Orange

Correct Answer: Violet

Q12. Resorcinol reacts with formaldehyde primarily to form:

• Polyurethane
• Resorcinol-formaldehyde resins (phenolic resins)
• Polyesters
• Stable ethers only

Correct Answer: Resorcinol-formaldehyde resins (phenolic resins)

Q13. In electrophilic aromatic substitution, the hydroxyl group in resorcinol is generally:

• A deactivating, meta-directing group
• An activating, ortho/para-directing group
• Electron-withdrawing by induction
• Unable to direct substitution

Correct Answer: An activating, ortho/para-directing group

Q14. Which analytical method is commonly used for quantitative assay of resorcinol in formulations?

• Thin layer chromatography only
• HPLC (High-Performance Liquid Chromatography)
• Flame photometry
• Polarimetry

Correct Answer: HPLC (High-Performance Liquid Chromatography)

Q15. Resorcinol’s solubility characteristics are best described as:

• Completely insoluble in organic solvents
• Highly soluble in water and many polar solvents
• Only soluble in nonpolar solvents
• Volatile and gas-phase soluble

Correct Answer: Highly soluble in water and many polar solvents

Q16. Which pharmaceutical use is resorcinol known for?

• Antihypertensive agent
• Topical antiseptic and keratolytic
• Oral antibiotic
• Systemic analgesic

Correct Answer: Topical antiseptic and keratolytic

Q17. What is a major industrial application of resorcinol outside pharmaceuticals?

• Fuel additive
• Precursor for dyes and resins (e.g., adhesives)
• Food preservative
• Explosive manufacture

Correct Answer: Precursor for dyes and resins (e.g., adhesives)

Q18. Which reaction is commonly used to detect phenolic OH groups including resorcinol qualitatively?

• Ninhydrin test
• Ferric chloride test
• Benedict’s test
• Salkowski test

Correct Answer: Ferric chloride test

Q19. Which safety precaution is important when handling resorcinol in the lab?

• No special precautions required
• Use of gloves and eye protection due to irritant properties
• Only avoid light exposure
• Store in open containers

Correct Answer: Use of gloves and eye protection due to irritant properties

Q20. Resorcinol in topical dermatologic formulations acts primarily by:

• Blocking melanogenesis enzyme directly
• Promoting desquamation of the stratum corneum (keratolytic effect)
• Systemic immunosuppression
• Hydrating deeper dermal layers

Correct Answer: Promoting desquamation of the stratum corneum (keratolytic effect)

Q21. Which derivative of resorcinol is commonly formed during electrophilic substitution at a free ring position?

• Resorcinol sulfate ester only
• Nitrated resorcinol (nitroresorcinol)
• Alkyl benzene exclusively
• Resorcinol chloride

Correct Answer: Nitrated resorcinol (nitroresorcinol)

Q22. Why is resorcinol more reactive than benzene toward electrophilic substitution?

• Because it is saturated
• Due to electron-donating hydroxyl groups increasing electron density
• Because it lacks aromaticity
• Because of a bulky substituent that activates the ring sterically

Correct Answer: Due to electron-donating hydroxyl groups increasing electron density

Q23. Resorcinol forms strong intermolecular hydrogen bonds which influence which physical property most directly?

• Optical rotation
• Melting point and solubility
• NMR chemical shift only
• Magnetic susceptibility

Correct Answer: Melting point and solubility

Q24. Which of the following statements about resorcinol-formaldehyde resins is true?

• They are produced by condensation polymerization of resorcinol with formaldehyde
• They decompose immediately in water
• They are produced by ionic polymerization without crosslinking
• They are identical to phenol-formaldehyde resins in properties

Correct Answer: They are produced by condensation polymerization of resorcinol with formaldehyde

Q25. In formulation chemistry, resorcinol is often incompatible with:

• Reducing agents only
• Oxidizing agents and strong bases that can oxidize phenols
• Neutral buffers exclusively
• Nonpolar solvents only

Correct Answer: Oxidizing agents and strong bases that can oxidize phenols

Q26. Which spectroscopic technique is useful to detect aromatic OH stretching in resorcinol?

• IR spectroscopy
• Flame emission spectroscopy
• Electron spin resonance
• Atomic absorption spectroscopy

Correct Answer: IR spectroscopy

Q27. For extracting resorcinol from aqueous solution into an organic solvent, which parameter is most important?

• pH of the aqueous phase
• Optical activity
• Magnetic stirring speed
• Atmospheric pressure only

Correct Answer: pH of the aqueous phase

Q28. Which is a common lab synthesis step used to prepare dihydroxybenzenes including resorcinol?

• Kolbe-Schmitt carboxylation exclusively
• Sulfonation followed by alkaline hydrolysis (fusion)
• Direct hydration of phenyl chloride
• Electrochemical methylation

Correct Answer: Sulfonation followed by alkaline hydrolysis (fusion)

Q29. Which property makes resorcinol useful in adhesives for wood and composite materials?

• Its volatility
• Ability to form cross-linked resins with formaldehyde
• Inertness to thermal curing
• High gas permeability

Correct Answer: Ability to form cross-linked resins with formaldehyde

Q30. Which biological effect is associated with topical resorcinol at therapeutic concentrations?

• Systemic anticoagulation
• Local antiseptic and keratolytic action
• Complete systemic absorption with CNS depression
• Photosensitization leading to UV protection

Correct Answer: Local antiseptic and keratolytic action

Q31. Which color is typically produced when resorcinol is treated with oxidizing agents (e.g., nitrous acid) in analytical tests?

• Colorless stable solution
• Complex color changes often producing colored products
• Bright green gas evolution
• Instant precipitation only

Correct Answer: Complex color changes often producing colored products

Q32. In HPLC analysis of resorcinol, which column type is commonly used?

• Size-exclusion column only
• Reversed-phase C18 column
• Ion-exchange column exclusively
• Gas chromatography column

Correct Answer: Reversed-phase C18 column

Q33. Which mobile phase modifier can improve peak shape for resorcinol in reversed-phase HPLC?

• Strong oxidizer
• Buffered aqueous-organic solvent (e.g., phosphate buffer with methanol)
• Pure hexane
• Neat acetonitrile without aqueous content for all assays

Correct Answer: Buffered aqueous-organic solvent (e.g., phosphate buffer with methanol)

Q34. Compared to hydroquinone (1,4-dihydroxybenzene), resorcinol’s hydroxyl arrangement is:

• Para arrangement
• Meta arrangement
• Ortho arrangement
• Non-aromatic

Correct Answer: Meta arrangement

Q35. Which formulation type commonly contains resorcinol as an active ingredient?

• Oral tablets for hypertension
• Topical creams and ointments for acne and eczema
• Injectable antibiotics
• Inhalation aerosols for asthma

Correct Answer: Topical creams and ointments for acne and eczema

Q36. Resorcinol’s ability to undergo electrophilic substitution is enhanced by which resonance effect?

• Negative hyperconjugation only
• Donating resonance of the phenolic OH into the aromatic ring
• Strong inductive electron withdrawal
• Sigma bonding to halogens

Correct Answer: Donating resonance of the phenolic OH into the aromatic ring

Q37. In a stability study, resorcinol-containing formulation exposed to light and air may:

• Remain completely unchanged indefinitely
• Undergo oxidation leading to discoloration and loss of potency
• Become more effective due to polymerization
• Turn into a volatile gas

Correct Answer: Undergo oxidation leading to discoloration and loss of potency

Q38. Which reagent is useful for selective derivatization of phenolic OH groups prior to chromatographic analysis?

• BSTFA (silylating agent)
• Sodium chloride only
• Hydrochloric acid gas
• Liquid nitrogen

Correct Answer: BSTFA (silylating agent)

Q39. Resorcinol’s antiseptic action is mainly due to:

• Specific inhibition of bacterial DNA polymerase only
• Protein denaturation and disruption of microbial cell membranes
• Selective fungal enzyme activation
• Acting as a surfactant without biocidal activity

Correct Answer: Protein denaturation and disruption of microbial cell membranes

Q40. When designing a topical formulation with resorcinol, which excipient class should be used cautiously?

• Nonreactive mineral oils only
• Strong oxidizing preservatives
• Simple emulsifiers like lecithin
• Water and glycerin blends

Correct Answer: Strong oxidizing preservatives

Q41. Which statement about resorcinol toxicity is correct?

• Resorcinol is non-toxic at any dose
• High exposure can cause systemic toxicity and skin irritation
• It acts as an immediate cardiac stimulant when applied topically
• It is an essential nutrient

Correct Answer: High exposure can cause systemic toxicity and skin irritation

Q42. In environmental terms, phenolic compounds like resorcinol are typically:

• Completely persistent and non-biodegradable
• Biodegradable under aerobic conditions but can be toxic at high concentrations
• Inert and non-toxic to aquatic life
• Volatile organochlorines

Correct Answer: Biodegradable under aerobic conditions but can be toxic at high concentrations

Q43. Which chromatographic detector is commonly paired with HPLC for sensitive detection of resorcinol?

• Flame ionization detector (FID)
• UV-Vis detector
• Conductivity detector only
• Beta counter

Correct Answer: UV-Vis detector

Q44. Which structural feature differentiates resorcinol from catechol?

• Number of carbon atoms
• Position of hydroxyl groups: resorcinol is 1,3-; catechol is 1,2-
• Presence of nitrogen in resorcinol
• Resorcinol is aliphatic while catechol is aromatic

Correct Answer: Position of hydroxyl groups: resorcinol is 1,3-; catechol is 1,2-

Q45. Which preservative strategy helps protect resorcinol-containing formulations from oxidative degradation?

• Including metal ion contaminants
• Adding antioxidants and chelating agents
• Storing at high temperature and light exposure
• Using strong oxidants as preservatives

Correct Answer: Adding antioxidants and chelating agents

Q46. What is a major reason resorcinol is used in hair dye chemistry?

• As a direct oxidizing dye itself
• As an intermediate that couples with other compounds after oxidation to form colored species
• As a bleaching agent that removes all pigments
• Because it permanently prevents hair growth

Correct Answer: As an intermediate that couples with other compounds after oxidation to form colored species

Q47. During formulation testing, you notice a declining assay of resorcinol over time. Which analytical check is most relevant?

• Measure pH and check for oxidative degradation products by HPLC
• Measure only viscosity
• Conduct a microbial challenge test only
• Check refractive index exclusively

Correct Answer: Measure pH and check for oxidative degradation products by HPLC

Q48. Resorcinol’s two hydroxyl groups influence its NMR spectrum primarily by:

• Eliminating all aromatic signals
• Shifting aromatic proton chemical shifts downfield due to deshielding and hydrogen bonding effects
• Causing radical signals at high field
• Producing only aliphatic signals

Correct Answer: Shifting aromatic proton chemical shifts downfield due to deshielding and hydrogen bonding effects

Q49. Which regulatory consideration is important when including resorcinol in an over-the-counter topical product?

• No labeling or safety data is required
• Appropriate concentration limits, safety data, and labeling for irritation risk are required
• It must be classified as a prescription-only systemic drug
• It is banned in all topical products

Correct Answer: Appropriate concentration limits, safety data, and labeling for irritation risk are required

Q50. In comparative reactivity, which statement is accurate?

• Resorcinol is less reactive than benzene due to deactivation
• Resorcinol is more reactive than benzene due to activating hydroxyl groups
• Resorcinol behaves identically to alkanes in substitution reactions
• Resorcinol cannot undergo electrophilic substitution

Correct Answer: Resorcinol is more reactive than benzene due to activating hydroxyl groups

Download