Structure and uses of vanillin MCQs With Answer

Introduction

Understanding the structure and uses of vanillin is essential for B.Pharm students studying pharmaceutical excipients, flavoring agents and organic intermediates. Vanillin (4-hydroxy-3-methoxybenzaldehyde) features an aromatic ring with aldehyde, phenolic hydroxyl and methoxy functional groups that determine its reactivity, physical properties and analytical behavior. This topic covers chemical structure, biosynthesis and industrial production routes (lignin, guaiacol, ferulic acid), spectral identification (IR, NMR, UV), chemical transformations (oxidation, reduction, derivatization), pharmaceutical applications (flavoring, masking, antioxidants) and regulatory status. These focused, exam-oriented MCQs will reinforce key concepts, spectral interpretation and formulation roles relevant to pharmacognosy, pharmaceutics and medicinal chemistry. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the IUPAC name of vanillin?

• 3-hydroxy-4-methoxybenzaldehyde
• 4-hydroxy-3-methoxybenzaldehyde
• 3-methoxy-4-hydroxybenzaldehyde
• 4-methoxy-3-hydroxybenzaldehyde

Correct Answer: 4-hydroxy-3-methoxybenzaldehyde

Q2. What is the molecular formula of vanillin?

• C7H6O3
• C8H8O3
• C9H10O3
• C8H6O4

Correct Answer: C8H8O3

Q3. Which functional groups are present in vanillin?

• Carboxylic acid, nitro, methoxy
• Aldehyde, phenolic hydroxyl, methoxy
• Ketone, phenolic hydroxyl, ethoxy
• Aldehyde, amine, methoxy

Correct Answer: Aldehyde, phenolic hydroxyl, methoxy

Q4. Vanillin is commonly produced industrially from which of the following feedstocks?

• Guaiacol and glyoxylic acid
• Salicylic acid and methanol
• Toluene and chlorine
• Phenol and acetone

Correct Answer: Guaiacol and glyoxylic acid

Q5. Which natural polymer is an important source for vanillin through depolymerization?

• Cellulose
• Lignin
• Starch
• Chitin

Correct Answer: Lignin

Q6. The aldehyde proton in vanillin appears in proton NMR at approximately which chemical shift?

• 0.9–1.5 ppm
• 3.6–3.9 ppm
• 7.0–8.0 ppm
• 9.5–10.0 ppm

Correct Answer: 9.5–10.0 ppm

Q7. The methoxy group in vanillin gives a singlet in 1H NMR at around:

• 0.9 ppm
• 2.0 ppm
• 3.7–3.9 ppm
• 7.5 ppm

Correct Answer: 3.7–3.9 ppm

Q8. Which reaction converts vanillin to vanillic acid?

• Reduction with NaBH4
• Oxidation of the aldehyde
• Methylation of the phenol
• Nitration of the aromatic ring

Correct Answer: Oxidation of the aldehyde

Q9. Vanillin gives a positive Tollens’ test because it contains which functional group?

• Phenolic hydroxyl
• Aldehyde
• Methoxy
• Aromatic ring only

Correct Answer: Aldehyde

Q10. Which derivative is known as ethyl vanillin?

• 4-hydroxy-3-ethoxybenzaldehyde
• 3-hydroxy-4-ethoxybenzaldehyde
• 4-ethoxy-3-methoxybenzaldehyde
• 3-ethoxy-4-methoxybenzaldehyde

Correct Answer: 4-hydroxy-3-ethoxybenzaldehyde

Q11. Which spectroscopic technique is most useful for identifying the conjugated aldehyde carbonyl in vanillin?

• Mass spectrometry
• Infrared (IR) spectroscopy
• Polarimetry
• Elemental analysis

Correct Answer: Infrared (IR) spectroscopy

Q12. A strong IR absorption around 1670 cm−1 in vanillin corresponds to:

• Phenolic O–H stretch
• Aromatic C=C stretch
• Conjugated aldehyde C=O stretch
• C–O–C ether stretch

Correct Answer: Conjugated aldehyde C=O stretch

Q13. In pharmaceutical formulations, vanillin is mainly used as a:

• Active pharmaceutical ingredient (API)
• Flavoring and masking agent
• Preservative
• Primary binder

Correct Answer: Flavoring and masking agent

Q14. Which analytical method is commonly used for quantitative determination of vanillin in formulations?

• Thin layer chromatography only
• HPLC with UV detection
• Titration with NaOH
• Direct visual inspection

Correct Answer: HPLC with UV detection

Q15. Vanillin is classified by the FDA as which of the following for food and pharmaceutical uses?

• Prescription drug
• GRAS (Generally Recognized as Safe)
• Controlled substance
• Not permitted for use

Correct Answer: GRAS (Generally Recognized as Safe)

Q16. Which microbial precursor is commonly biotransformed to vanillin in biotechnological processes?

• Benzoic acid
• Ferulic acid
• Citric acid
• Acetic acid

Correct Answer: Ferulic acid

Q17. Reduction of the aldehyde group of vanillin yields which compound?

• Vanillic acid
• Vanillyl alcohol
• Vanillic aldehyde
• Vanillin acetate

Correct Answer: Vanillyl alcohol

Q18. Which property of vanillin contributes to its role as a masking agent in oral syrups?

• High melting point
• Distinct sweet aromatic flavor and odor
• Strong antiseptic activity
• High aqueous solubility

Correct Answer: Distinct sweet aromatic flavor and odor

Q19. Vanillin’s aromatic ring is activated towards electrophilic substitution primarily by which group?

• Methoxy group (–OCH3)
• Aldehyde group (–CHO)
• Nitro group (–NO2)
• Carboxyl group (–COOH)

Correct Answer: Methoxy group (–OCH3)

Q20. Which of the following is a common chemical test to derivatize the aldehyde of vanillin for analytical detection?

• Formation of dinitrophenylhydrazone (DNPH)
• Esterification with methanol
• Diazotization
• Peroxide formation

Correct Answer: Formation of dinitrophenylhydrazone (DNPH)

Q21. Which solvent pair is commonly used for HPLC analysis of vanillin?

• Water–acetonitrile
• Hexane–ethyl acetate
• Carbon tetrachloride–methanol
• Petroleum ether–chloroform

Correct Answer: Water–acetonitrile

Q22. Vanillin shows antioxidant activity primarily because of which feature?

• Aldehyde group donating electrons
• Phenolic hydroxyl capable of hydrogen donation
• Methoxy group forming radicals
• Aromatic ring only

Correct Answer: Phenolic hydroxyl capable of hydrogen donation

Q23. Which of the following best describes vanillin’s solubility?

• Highly soluble in water
• Insoluble in common organic solvents
• Soluble in ethanol and organic solvents but limited in water
• Only soluble in oils

Correct Answer: Soluble in ethanol and organic solvents but limited in water

Q24. The typical melting point range of pure vanillin is approximately:

• 20–25 °C
• 60–62 °C
• 81–83 °C
• 150–155 °C

Correct Answer: 81–83 °C

Q25. Which chromatography method coupled with mass spectrometry is useful for identifying vanillin in complex matrices?

• Gas chromatography–mass spectrometry (GC–MS)
• Paper chromatography
• Size exclusion chromatography
• Ion exchange chromatography

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

Q26. In medicinal chemistry, vanillin is often used as:

• A starting material for synthesis of more complex molecules
• A controlled drug substance
• A strong acid catalyst
• An isotonic agent

Correct Answer: A starting material for synthesis of more complex molecules

Q27. Which position on the benzene ring of vanillin bears the methoxy substituent?

• Position 1 (aldehyde carbon)
• Position 2 (ortho to aldehyde)
• Position 3 (meta to aldehyde)
• Position 4 (para to aldehyde)

Correct Answer: Position 3 (meta to aldehyde)

Q28. Which reagent selectively reduces the aldehyde group of vanillin to the corresponding alcohol under mild conditions?

• PCC (pyridinium chlorochromate)
• LiAlH4 in ether
• NaBH4 in ethanol
• Chromic acid

Correct Answer: NaBH4 in ethanol

Q29. Vanillin can be converted to Schiff bases by reaction with:

• Primary amines
• Carboxylic acids
• Alcohols
• Alkyl halides

Correct Answer: Primary amines

Q30. Which statement about vanillin’s role in topical pharmaceutical formulations is correct?

• Vanillin acts as a primary antimicrobial preservative
• Vanillin is used mainly as a fragrance or odor masker
• Vanillin is used as a gelling agent
• Vanillin is a common UV absorber in creams

Correct Answer: Vanillin is used mainly as a fragrance or odor masker

Q31. A student analyzing vanillin by UV–Vis spectroscopy would most likely monitor the absorbance near which region?

• 200–220 nm
• 250–300 nm
• 400–450 nm
• 600–700 nm

Correct Answer: 250–300 nm

Q32. Which oxidative biotransformation is industrially used to obtain vanillin from lignin?

• Hydrolytic decarboxylation
• Oxidative depolymerization
• Hydrogenation of aromatic rings
• Reduction of ketones

Correct Answer: Oxidative depolymerization

Q33. Which of the following is a common impurity in crude vanillin obtained from lignin?

• Vanillyl alcohol
• Glucose
• Sucrose
• Benzoic acid

Correct Answer: Vanillyl alcohol

Q34. Vanillin forms which type of protective derivative with 2,4-dinitrophenylhydrazine (DNPH)?

• Hydrazone
• Oxime
• Thioether
• Acetal

Correct Answer: Hydrazone

Q35. Which factor most strongly affects the odor perception of vanillin in formulations?

• pH of the formulation
• Particle size only
• Presence of water only
• Concentration and volatility

Correct Answer: Concentration and volatility

Q36. Which solvent would most likely dissolve vanillin readily for preparative chemistry?

• Diethyl ether
• Water at room temperature
• Ethanol
• n-Hexane

Correct Answer: Ethanol

Q37. Which chemical modification increases the lipophilicity of vanillin for formulation studies?

• Oxidation of the aldehyde to acid
• Acetylation of the phenolic OH
• Hydrogenation of the aromatic ring
• Conversion to the DNPH derivative

Correct Answer: Acetylation of the phenolic OH

Q38. Vanillin exhibits antimicrobial effects primarily due to:

• Its strong basicity
• Phenolic structure disrupting microbial membranes and enzyme systems
• High acidity killing bacteria
• Being a powerful oxidant

Correct Answer: Phenolic structure disrupting microbial membranes and enzyme systems

Q39. In TLC analysis of vanillin, what visualization reagent would reveal the phenolic compound?

• Dragendorff’s reagent
• ninhydrin
• Vanillin-sulfuric acid reagent
• Silver nitrate solution

Correct Answer: Vanillin-sulfuric acid reagent

Q40. Which of the following is NOT a common route to synthesize vanillin?

• From guaiacol
• From eugenol via oxidative cleavage
• Direct extraction from petroleum crude oil
• Bioconversion of ferulic acid

Correct Answer: Direct extraction from petroleum crude oil

Q41. What is a primary environmental advantage of biotechnological production of vanillin from ferulic acid?

• Higher energy consumption
• Lower selectivity
• Use of renewable feedstock and milder conditions
• Greater generation of toxic byproducts

Correct Answer: Use of renewable feedstock and milder conditions

Q42. Which atom count corresponds to vanillin’s number of oxygen atoms?

• One oxygen atom
• Two oxygen atoms
• Three oxygen atoms
• Four oxygen atoms

Correct Answer: Three oxygen atoms

Q43. In structure-activity studies, modification of vanillin’s phenolic OH often alters which property?

• Optical rotation only
• Flavor profile and antioxidant activity
• Atomic weight
• Number of carbons

Correct Answer: Flavor profile and antioxidant activity

Q44. Which laboratory reagent would selectively methylate the phenolic OH in vanillin to form methylated derivatives?

• Sodium borohydride (NaBH4)
• Diazomethane
• PCC (pyridinium chlorochromate)
• Sodium hydroxide only

Correct Answer: Diazomethane

Q45. Which safety statement about vanillin is most appropriate for pharmacists?

• Vanillin is non-toxic at any dose and requires no handling precautions
• Vanillin is an explosive compound and must be stored under inert atmosphere
• Vanillin is generally safe but may cause irritation or allergic reaction in sensitive individuals
• Vanillin is a Schedule I controlled drug

Correct Answer: Vanillin is generally safe but may cause irritation or allergic reaction in sensitive individuals

Q46. Which transformation converts vanillin into an ether derivative by replacing the phenolic hydrogen?

• Etherification (alkylation) of the phenolic OH
• Hydrogenation of aldehyde
• Oxidative cleavage of aromatic ring
• Formation of a hydrazone

Correct Answer: Etherification (alkylation) of the phenolic OH

Q47. Which solvent system is most appropriate for extracting vanillin from aqueous reaction mixtures?

• n-Hexane
• Ethyl acetate
• Water only
• Liquid ammonia

Correct Answer: Ethyl acetate

Q48. Which is a common pharmacological study area where vanillin is used as a model compound?

• Anticoagulant mechanism studies
• Permeation enhancement and drug delivery flavor masking
• Insulin replacement research
• Radioactive tracer synthesis

Correct Answer: Permeation enhancement and drug delivery flavor masking

Q49. Which of the following statements about vanillin stability is correct?

• Vanillin is highly stable to strong oxidizing agents
• Vanillin is stable under all pH conditions without degradation
• Vanillin is sensitive to strong oxidizing conditions and prolonged heating
• Vanillin cannot be oxidized under laboratory conditions

Correct Answer: Vanillin is sensitive to strong oxidizing conditions and prolonged heating

Q50. Which application area beyond flavor and fragrance increasingly explores vanillin derivatives?

• Semiconductor manufacturing
• Pharmaceutical intermediates and medicinal chemistry
• Asphalt production
• Explosive manufacturing

Correct Answer: Pharmaceutical intermediates and medicinal chemistry

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