Structure and uses of cresols MCQs With Answer

Cresols are methyl-substituted phenols (o-, m-, p-cresol) important in pharmaceutical chemistry for their unique structure and uses. B.Pharm students must understand cresol isomerism, nomenclature, aromatic reactivity, acidity, spectroscopy, toxicity, and industrial applications such as antiseptics, creosotes, and cresol-formaldehyde resins. Knowledge of electrophilic substitution patterns (OH and CH3 are ortho/para directors), oxidation products, analytical identification (GC-MS, IR, NMR), and safe handling is essential for formulation and medicinal chemistry. This focused overview prepares you for exam-style questions and practical lab considerations. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the molecular formula of cresols?

• C6H6O
• C7H8O
• C8H8O2
• C7H6O2

Correct Answer: C7H8O

Q2. What are the IUPAC names of the three cresol isomers?

• 2-Methylphenol, 3-Methylphenol, 4-Methylphenol
• 2-Ethylphenol, 3-Ethylphenol, 4-Ethylphenol
• Methylphenol, Dimethylphenol, Trimethylphenol
• Phenol, Toluenol, Benzylalcohol

Correct Answer: 2-Methylphenol, 3-Methylphenol, 4-Methylphenol

Q3. How many structural isomers of cresol exist?

• 2
• 3
• 4
• 5

Correct Answer: 3

Q4. Which industrial source is historically major for obtaining cresols?

• Petroleum refining only
• Coal tar
• Vegetable oil extraction
• Synthetic polymer waste

Correct Answer: Coal tar

Q5. Which functional groups are present in cresols?

• Aldehyde and methyl
• Phenolic hydroxyl and methyl
• Carboxyl and methoxy
• Amine and nitro

Correct Answer: Phenolic hydroxyl and methyl

Q6. What is the approximate molar mass of cresols (C7H8O)?

• 94 g/mol
• 108 g/mol
• 122 g/mol
• 136 g/mol

Correct Answer: 108 g/mol

Q7. What is the physical state of cresols at room temperature?

• Colorless gases
• Solid crystalline salts
• Colorless to yellowish liquids
• Stable aqueous solutions

Correct Answer: Colorless to yellowish liquids

Q8. Among the cresol isomers, which one typically has the highest melting point due to molecular symmetry?

• o-Cresol (2-methylphenol)
• m-Cresol (3-methylphenol)
• p-Cresol (4-methylphenol)
• All have identical melting points

Correct Answer: p-Cresol (4-methylphenol)

Q9. How does the acidity of cresols compare to phenol?

• Cresols are significantly more acidic than phenol
• Cresols are slightly less acidic than phenol
• Cresols have identical acidity to phenol
• Cresols are non-acidic

Correct Answer: Cresols are slightly less acidic than phenol

Q10. Which cresol isomer is generally the least acidic due to steric hindrance reducing solvation of the phenoxide?

• p-Cresol
• m-Cresol
• o-Cresol
• All are equally acidic

Correct Answer: o-Cresol

Q11. In electrophilic aromatic substitution reactions on cresols, which directions are activated by -OH and -CH3 substituents?

• Meta only
• Ortho and para, with -OH being the stronger ortho/para director
• Para only
• Deactivating to all positions

Correct Answer: Ortho and para, with -OH being the stronger ortho/para director

Q12. Nitration of cresols typically introduces nitro groups at which positions relative to the hydroxyl group?

• Meta positions only
• Ortho and para positions to the hydroxyl group
• Only at the methyl carbon
• No nitration occurs on cresols

Correct Answer: Ortho and para positions to the hydroxyl group

Q13. Which reagent pair is commonly used for nitration of aromatic phenolic compounds like cresols?

• HCl and Zn
• HNO3 and H2SO4
• NaBH4 and EtOH
• KMnO4 and NaOH

Correct Answer: HNO3 and H2SO4

Q14. Strong oxidation of the methyl side chain in cresols (e.g., with KMnO4) typically yields which type of compound?

• Alkylbenzene
• Hydroxybenzoic acids (ring carboxylation of the methyl group)
• Alkane and CO2 only
• No reaction under oxidizing conditions

Correct Answer: Hydroxybenzoic acids (ring carboxylation of the methyl group)

Q15. Which major industrial application involves cresols reacting with formaldehyde?

• Polyethylene production
• Cresol-formaldehyde phenolic resins
• Polyvinyl chloride synthesis
• Polystyrene manufacture

Correct Answer: Cresol-formaldehyde phenolic resins

Q16. Historically and currently, cresols are widely used as:

• Sweetening agents in foods
• Antiseptics and disinfectants
• Primary components of hand sanitizers (alcohol-based)
• Direct oral medications

Correct Answer: Antiseptics and disinfectants

Q17. Which commercial mixture name refers to a blend of cresols and related phenolics used for disinfectants and preservatives?

• Creosote
• Cresylic acid
• Phenylalanine
• Coal oil

Correct Answer: Cresylic acid

Q18. How soluble are cresols in water at room temperature?

• Completely miscible
• Highly insoluble (zero solubility)
• Only slightly to moderately soluble due to the phenolic OH
• Soluble only when heated above 100°C

Correct Answer: Only slightly to moderately soluble due to the phenolic OH

Q19. Are cresols soluble in common organic solvents like ethanol and ether?

• No, they are insoluble in organic solvents
• Yes, they are soluble in many organic solvents
• Only soluble in water-miscible solvents above pH 12
• Only soluble in supercritical CO2

Correct Answer: Yes, they are soluble in many organic solvents

Q20. What is the molecular ion (M+) peak expected for cresols in mass spectrometry (m/z)?

• m/z 94
• m/z 108
• m/z 122
• m/z 140

Correct Answer: m/z 108

Q21. In IR spectroscopy, which band indicates the presence of the phenolic O–H in cresols?

• A sharp band near 1700 cm⁻¹
• A broad band around 3200–3600 cm⁻¹
• A single peak at 2100 cm⁻¹
• No characteristic O–H band is observed

Correct Answer: A broad band around 3200–3600 cm⁻¹

Q22. The 1H NMR spectrum of p-cresol typically shows how many distinct aromatic proton environments?

• One
• Two (an A2B2 pattern)
• Three
• Four all non-equivalent

Correct Answer: Two (an A2B2 pattern)

Q23. Treating cresol with sodium hydroxide produces a water-soluble species. What is formed?

• Alkoxide
• Phenoxide (sodium cresoxide) salt
• Carbanion of methyl group
• No reaction occurs

Correct Answer: Phenoxide (sodium cresoxide) salt

Q24. Which simple qualitative test can be used to indicate the presence of a phenolic OH like in cresols?

• Tollens’ test (silver mirror)
• Ferric chloride producing colored complex
• Benedict’s test
• Lucas reagent only

Correct Answer: Ferric chloride producing colored complex

Q25. The methyl group on the aromatic ring in cresols exerts which electronic effect?

• Strong electron-withdrawing by induction
• Electron-donating by hyperconjugation (activating)
• Resonance electron-withdrawing
• No electronic effect

Correct Answer: Electron-donating by hyperconjugation (activating)

Q26. Between -OH and -CH3 substituents on the aromatic ring, which predominately controls orientation for electrophilic substitution?

• -CH3 dominates and directs meta
• -OH dominates and directs ortho/para
• Both cancel out and yield no reaction
• Only steric factors control orientation

Correct Answer: -OH dominates and directs ortho/para

Q27. Which reagent is commonly used to protect the phenolic OH of cresols as an acetate in synthesis?

• Thionyl chloride (SOCl2)
• Acetic anhydride (Ac2O)
• Sodium borohydride (NaBH4)
• Ozone (O3)

Correct Answer: Acetic anhydride (Ac2O)

Q28. Methylation of the phenolic OH of cresol to form an ether can be achieved using which reagent?

• Diazomethane (CH2N2)
• Potassium permanganate (KMnO4)
• Hydrochloric acid (HCl)
• Sodium hydroxide (NaOH) alone

Correct Answer: Diazomethane (CH2N2)

Q29. Industrial synthesis of cresols can involve methylation of phenol. This statement is:

• True
• False
• True only for p-cresol
• False; cresols cannot be made from phenol

Correct Answer: True

Q30. Which analytical technique is most suitable to separate and identify cresol isomers in a complex mixture?

• Infrared spectroscopy alone
• Gas chromatography–mass spectrometry (GC-MS)
• Simple paper chromatography
• Polarimetry

Correct Answer: Gas chromatography–mass spectrometry (GC-MS)

Q31. Bromination of cresols in an aqueous medium often leads to which outcome?

• No reaction due to deactivation
• Rapid polybromination at activated ortho/para positions
• Substitution of the methyl group only
• Oxidative cleavage of the aromatic ring

Correct Answer: Rapid polybromination at activated ortho/para positions

Q32. Which cresol isomer is most symmetric and often gives simpler spectroscopic patterns?

• o-Cresol
• m-Cresol
• p-Cresol
• All are equally symmetric

Correct Answer: p-Cresol

Q33. Are cresols chiral compounds?

• Yes, all cresols are chiral
• Only o-cresol is chiral
• No, cresols are achiral
• Only p-cresol is chiral

Correct Answer: No, cresols are achiral

Q34. Human metabolism of cresols majorly proceeds by which conjugation pathways?

• Nitration and halogenation
• Glucuronidation and sulfation
• Polymerization in vivo
• Complete excretion unchanged only

Correct Answer: Glucuronidation and sulfation

Q35. What are primary health hazards associated with cresol exposure?

• Non-toxic and safe for ingestion
• Corrosive to skin, irritant to eyes and respiratory tract, systemic toxicity on absorption
• Only allergic rhinitis in sensitive individuals
• Beneficial nutritional supplement

Correct Answer: Corrosive to skin, irritant to eyes and respiratory tract, systemic toxicity on absorption

Q36. In case of skin contact with cresol, the immediate appropriate first aid is:

• Rinse with copious water and remove contaminated clothing
• Apply concentrated acid to neutralize
• Cover with oil and wait
• Do nothing and seek no treatment

Correct Answer: Rinse with copious water and remove contaminated clothing

Q37. Which environmental compartment are cresols commonly monitored in due to contamination risk?

• Deep space samples
• Surface water and soil
• Outer atmosphere at 80 km altitude
• Pure distilled water only

Correct Answer: Surface water and soil

Q38. Which polymer application benefits from cresol chemistry?

• Polyethylene terephthalate (PET) production
• Phenolic resins used in adhesives and molding compounds
• Polypropylene fiber spinning
• Polyacrylamide gel electrophoresis matrices

Correct Answer: Phenolic resins used in adhesives and molding compounds

Q39. Cresols are valuable intermediates in the synthesis of which types of products?

• Pharmaceuticals, agrochemicals, dyes and antioxidants
• Only water-soluble vitamins
• Exclusively food preservatives
• Radioactive tracers only

Correct Answer: Pharmaceuticals, agrochemicals, dyes and antioxidants

Q40. Which reaction converts a cresol methyl side chain into a carboxyl group under strong oxidative conditions?

• Hydrogenation
• Oxidation with potassium permanganate (KMnO4)
• Reduction with LiAlH4
• Friedel–Crafts alkylation

Correct Answer: Oxidation with potassium permanganate (KMnO4)

Q41. The Kolbe–Schmitt reaction applied to phenoxides introduces which functional group onto the ring?

• Nitro group
• Carboxyl group (via CO2 fixation at ortho position)
• Alkyl group only
• Sulfate ester

Correct Answer: Carboxyl group (via CO2 fixation at ortho position)

Q42. Which laboratory protection is commonly used when handling cresols due to dermal absorption risk?

• Disposable nitrile gloves and eye protection
• No protection required for small amounts
• Only a cloth mask
• Latex balloons

Correct Answer: Disposable nitrile gloves and eye protection

Q43. Which statement about cresol esters (cresyl esters) is correct?

• Cresols cannot form esters
• Cresols form esters upon reaction with acyl chlorides or anhydrides at the phenolic OH
• Cresyl esters are formed by hydrogenation only
• Formation of esters destroys the aromatic ring

Correct Answer: Cresols form esters upon reaction with acyl chlorides or anhydrides at the phenolic OH

Q44. Which reagent selectively converts the phenolic OH to an ether (O-methylation) in the lab?

• Potassium tert-butoxide alone
• Dimethyl sulfate or methyl iodide with base, or diazomethane
• Hydrochloric acid
• Chromic acid (H2CrO4)

Correct Answer: Dimethyl sulfate or methyl iodide with base, or diazomethane

Q45. Which aromatic position in cresols has the highest electron density and is most susceptible to electrophilic attack?

• Positions meta to the hydroxyl group
• Positions ortho and para to the hydroxyl group
• The methyl carbon only
• Positions para to the methyl group only

Correct Answer: Positions ortho and para to the hydroxyl group

Q46. Which industrial application of cresols involves wood protection?

• Wood preservatives in creosote formulations
• Natural varnish replacement
• Food-grade coating for wood
• None; cresols are not used in wood treatment

Correct Answer: Wood preservatives in creosote formulations

Q47. Environmental regulations often monitor cresols because they are:

• Non-volatile and permanently bound to soil
• Toxic, bioactive, and can contaminate water and soil
• Beneficial nutrients for aquatic life
• Completely inert and harmless

Correct Answer: Toxic, bioactive, and can contaminate water and soil

Q48. Which technique provides structural information about substitution pattern (o-, m-, p-) in cresols using splitting and chemical shift?

• Thin-layer chromatography (TLC)
• 1H NMR spectroscopy
• Simple boiling point comparison only
• Colorimetric pH strips

Correct Answer: 1H NMR spectroscopy

Q49. Which statement about cresol reactivity is true?

• Cresols are strongly deactivating and resist electrophilic substitution
• Cresols are activated aromatics and undergo electrophilic substitution more readily than benzene
• Cresols cannot undergo oxidation
• Cresols are inert under acidic conditions

Correct Answer: Cresols are activated aromatics and undergo electrophilic substitution more readily than benzene

Q50. Which metabolic or analytical observation is commonly used to assess occupational exposure to cresols?

• Measurement of urinary cresol conjugates (glucuronides/sulfates)
• Hair strand color change only
• Blood transfusion requirement
• Monitoring breath oxygen content exclusively

Correct Answer: Measurement of urinary cresol conjugates (glucuronides/sulfates)

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