Structure and uses of glycerol MCQs With Answer

Introduction: Glycerol, a tri-hydroxy alcohol with molecular formula C3H8O3, is a key excipient in pharmaceutical science. B.Pharm students must understand the structure of glycerol, its stereochemistry, physicochemical properties, pharmaceutical uses as a humectant, solvent, plasticizer and preservative, and its role in formulations like syrups, ointments and suppositories. Knowledge of glycerol pharmacopoeial standards, metabolic pathways and common reactions (esterification, oxidation) is essential for drug design and quality control. This set of focused, exam-oriented glycerol MCQs with answers will deepen your conceptual understanding and application skills. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the molecular formula of glycerol?

• C3H8O3
• C3H6O3
• C3H7O2
• C2H6O

Correct Answer: C3H8O3

Q2. Which functional groups are present in glycerol?

• Three hydroxyl groups
• One carboxyl and two hydroxyl groups
• Two hydroxyl and one aldehyde group
• One amino and two hydroxyl groups

Correct Answer: Three hydroxyl groups

Q3. Glycerol is best classified as which type of alcohol?

• Primary alcohol
• Secondary alcohol
• Tertiary alcohol
• Polyol (triol)

Correct Answer: Polyol (triol)

Q4. Which structural feature gives glycerol its hygroscopic property?

• Multiple hydroxyl groups capable of hydrogen bonding
• Presence of a long hydrocarbon chain
• Carbonyl functionality
• Aromatic ring structure

Correct Answer: Multiple hydroxyl groups capable of hydrogen bonding

Q5. Which pathway metabolizes glycerol in the liver?

• Glycerol → glycerol-3-phosphate → dihydroxyacetone phosphate (glycolytic pathway)
• Glycerol → acetyl-CoA directly
• Glycerol → lactic acid in mitochondria
• Glycerol is excreted unchanged

Correct Answer: Glycerol → glycerol-3-phosphate → dihydroxyacetone phosphate (glycolytic pathway)

Q6. Which of the following is a major pharmaceutical use of glycerol?

• Humectant in topical formulations
• Active antimicrobial agent
• Primary filtration medium
• Radiopaque contrast agent

Correct Answer: Humectant in topical formulations

Q7. In ointment formulations, glycerol is primarily used as a:

• Humectant and co-solvent
• Main emulsifier
• Surfactant for foaming
• Antioxidant

Correct Answer: Humectant and co-solvent

Q8. Which reaction converts glycerol into triglycerides?

• Esterification with fatty acids
• Hydrogenation
• Nitration
• Oxidative cleavage

Correct Answer: Esterification with fatty acids

Q9. Which glycerol derivative is used as an explosive in medicine history?

• Nitroglycerin
• Glycerol carbonate
• Propylene glycol

Correct Answer: Nitroglycerin

Q10. Which property of glycerol makes it suitable as a solvent for many drugs?

• High polarity and hydrogen-bonding capacity
• Strong basicity
• Low boiling point
• Hydrophobic character

Correct Answer: High polarity and hydrogen-bonding capacity

Q11. Glycerol passes most pharmacopoeial purity tests except when contaminated with:

• Mono- and diglycerides from incomplete purification
• Sodium chloride
• Cellulose
• Silicon dioxide

Correct Answer: Mono- and diglycerides from incomplete purification

Q12. Which analytical test is commonly used to quantify glycerol in formulations?

• HPLC with refractive index or evaporative light scattering detection
• UV-visible spectrophotometry at 280 nm
• Flame photometry
• Atomic absorption spectroscopy

Correct Answer: HPLC with refractive index or evaporative light scattering detection

Q13. During esterification of glycerol, which positions can be esterified?

• All three hydroxyl positions (sn-1, sn-2, sn-3)
• Only the central hydroxyl
• Only terminal hydroxyls
• No hydroxyls can be esterified

Correct Answer: All three hydroxyl positions (sn-1, sn-2, sn-3)

Q14. Glycerol’s boiling point is relatively high due to:

• Extensive hydrogen bonding between molecules
• Very low molecular weight
• Presence of aromatic rings
• Ionic bonding between molecules

Correct Answer: Extensive hydrogen bonding between molecules

Q15. In suppository bases, glycerol is used because it acts as a:

• Wetting agent and humectant to improve drug release
• Primary solidifying agent
• Permeation enhancer by lipid disruption
• Gelling agent forming crosslinked networks

Correct Answer: Wetting agent and humectant to improve drug release

Q16. Which statement about glycerol stereochemistry is correct?

• Glycerol is achiral because the central carbon is attached to two identical groups
• Glycerol has one chiral center making it optically active
• Glycerol exists as enantiomers in solution
• Glycerol is meso due to internal compensation

Correct Answer: Glycerol is achiral because the central carbon is attached to two identical groups

Q17. Which reaction is commonly used industrially to produce glycerol as a by-product?

• Transesterification of triglycerides during biodiesel production
• Direct oxidation of ethylene
• Polymerization of propylene oxide
• Fermentation of glucose to ethanol

Correct Answer: Transesterification of triglycerides during biodiesel production

Q18. In pharmaceutical syrups, glycerol helps primarily to:

• Increase sweetness and viscosity while acting as a preservative
• Act as the primary active ingredient
• Reduce syrup stability
• Precipitate suspended solids

Correct Answer: Increase sweetness and viscosity while acting as a preservative

Q19. Which safety concern is associated with glycerol in parenteral formulations?

• Osmolarity effects, causing hemolysis or renal burden at high concentrations
• Direct cardiotoxicity at low doses
• Strong immunogenicity
• Carcinogenicity

Correct Answer: Osmolarity effects, causing hemolysis or renal burden at high concentrations

Q20. Glycerol can act as a cryoprotectant by:

• Reducing ice crystal formation through hydrogen bonding with water
• Increasing freezing point of solutions drastically
• Reacting chemically with proteins to stabilize them
• Forming micelles around cells

Correct Answer: Reducing ice crystal formation through hydrogen bonding with water

Q21. Which test would identify glycerol adulteration with diethylene glycol?

• GC-MS analysis to separate and identify low molecular weight glycols
• pH measurement
• Visual color inspection only
• Simple density measurement without chromatography

Correct Answer: GC-MS analysis to separate and identify low molecular weight glycols

Q22. Which property of glycerol influences drug permeation through skin when used in formulations?

• Its hygroscopic nature altering stratum corneum hydration
• High volatility
• Strong surfactant activity
• Large hydrophobic domain

Correct Answer: Its hygroscopic nature altering stratum corneum hydration

Q23. Glycerol’s IUPAC name is:

• Propane-1,2,3-triol
• 2-Propanol
• Propane-2-one
• 1,3-Dihydroxypropane

Correct Answer: Propane-1,2,3-triol

Q24. Which of the following is a common pharmaceutical impurity test for glycerol?

• Determination of free acids and esters by saponification value or chromatographic assays
• Measurement of potassium permanganate reduction only
• Test for sulfated ash
• Test for particulate matter under electron microscopy

Correct Answer: Determination of free acids and esters by saponification value or chromatographic assays

Q25. Compared to propylene glycol, glycerol is:

• Less volatile and more viscous with higher hygroscopicity
• More volatile and less viscous
• Less hygroscopic and nonpolar
• Stronger oxidizing agent

Correct Answer: Less volatile and more viscous with higher hygroscopicity

Q26. Which enzyme catalyzes the phosphorylation of glycerol to glycerol-3-phosphate?

• Glycerol kinase
• Alcohol dehydrogenase
• Glyceraldehyde dehydrogenase
• Lipase

Correct Answer: Glycerol kinase

Q27. In topical formulations, excessive glycerol concentration may cause:

• Sticky feel and potential skin irritation due to hyperosmolarity
• Increased volatilization causing dryness
• Reduced solubility of actives by forming covalent bonds
• Spontaneous polymerization

Correct Answer: Sticky feel and potential skin irritation due to hyperosmolarity

Q28. Which chemical test can distinguish glycerol from other polyols?

• Periodate oxidation followed by analysis of cleavage products
• Simple Benedict’s test for reducing sugars
• Flame test for sodium content
• Biuret test for proteins

Correct Answer: Periodate oxidation followed by analysis of cleavage products

Q29. Glyceryl monooleate is primarily used in pharmaceuticals as a:

• Nonionic surfactant and emulsifier for controlled-release systems
• Systemic vasoconstrictor
• Preservative against fungi only
• Metal chelator

Correct Answer: Nonionic surfactant and emulsifier for controlled-release systems

Q30. Which statement about glycerol toxicity is true?

• Glycerol has low acute toxicity but high doses can cause osmotic disturbances
• Glycerol is highly toxic and lethal at microgram doses
• Glycerol causes irreversible DNA damage at therapeutic doses
• Glycerol is non-metabolizable and accumulates indefinitely

Correct Answer: Glycerol has low acute toxicity but high doses can cause osmotic disturbances

Q31. Which pharmaceutical test assesses glycerol’s water content?

• Karl Fischer titration
• TLC with ninhydrin
• Melting point determination
• Gel permeation chromatography

Correct Answer: Karl Fischer titration

Q32. In transdermal formulations, glycerol can influence drug permeation by:

• Hydrating the stratum corneum and modifying partitioning of the drug
• Acting as an irreversible enzyme inhibitor in skin
• Decreasing drug solubility in the vehicle only
• Increasing skin thickness permanently

Correct Answer: Hydrating the stratum corneum and modifying partitioning of the drug

Q33. Which pharmaceutical grade designation indicates glycerol meeting international compendial standards?

• Ph.Eur./USP grade glycerol
• Food grade only
• Industrial crude glycerol
• Technical solvent grade

Correct Answer: Ph.Eur./USP grade glycerol

Q34. Glycerol’s osmotic laxative effect when administered orally is due to:

• Drawing water into the intestinal lumen increasing peristalsis
• Direct stimulation of opioid receptors
• Neutralizing gastric acid
• Blocking chloride channels in enterocytes

Correct Answer: Drawing water into the intestinal lumen increasing peristalsis

Q35. Which derivative of glycerol is commonly used as a plasticizer in pharmaceutical films?

• Triacetin (glycerol triacetate)
• Glycerol aldehyde
• Nitroglycerin
• Glycerol sulfate

Correct Answer: Triacetin (glycerol triacetate)

Q36. During saponification of fats, glycerol is produced by:

• Hydrolysis of triglycerides to glycerol and fatty acid salts
• Oxidative cleavage of fatty acids only
• Polymerization of glyceraldehyde
• Dehydration of fatty alcohols

Correct Answer: Hydrolysis of triglycerides to glycerol and fatty acid salts

Q37. Which solvent property of glycerol affects its use in topical drug delivery?

• High viscosity which can control drug release and skin contact time
• High volatility that causes rapid evaporation
• Strong alkalinity causing irritation
• Ionic conductivity enabling electrotransport

Correct Answer: High viscosity which can control drug release and skin contact time

Q38. Glycerol can stabilize proteins in formulations primarily by:

• Preferential exclusion leading to protein folding stabilization
• Direct covalent modification of amino acids
• Acting as an oxidizing agent to create disulfide bonds
• Denaturing proteins at low concentrations

Correct Answer: Preferential exclusion leading to protein folding stabilization

Q39. Which of the following is a correct statement about glyceryl esters?

• Mono-, di- and triglycerides differ by the number of esterified hydroxyls
• All glyceryl esters are fully hydrophilic
• Glyceryl esters cannot be used as emulsifiers
• Glyceryl esters are volatile liquids at room temperature

Correct Answer: Mono-, di- and triglycerides differ by the number of esterified hydroxyls

Q40. Which method is suitable to remove residual solvents from glycerol in pharmaceutical manufacturing?

• Vacuum distillation due to glycerol’s high boiling point and vacuum sensitivity
• Simple air drying at room temperature only
• Freezing and filtration
• Microwave irradiation without control

Correct Answer: Vacuum distillation due to glycerol’s high boiling point and vacuum sensitivity

Q41. For parenteral use, glycerol concentration should be controlled because it can affect:

• Solution tonicity and patient osmotic balance
• Color of the drug only
• pH exclusively without other effects
• Sterility without filtration

Correct Answer: Solution tonicity and patient osmotic balance

Q42. Which reagent oxidizes glycerol to glyceric acid or dihydroxyacetone depending on conditions?

• Periodic acid or specific oxidizing agents under controlled conditions
• Sodium borohydride
• Hydrochloric acid alone
• Hydrogen gas without catalyst

Correct Answer: Periodic acid or specific oxidizing agents under controlled conditions

Q43. In topical drug delivery, glycerol can act synergistically with alcohols to:

• Enhance solubility of actives while maintaining skin hydration
• Prevent any drug penetration entirely
• Cause irreversible keratinocyte death
• Convert drugs into ionic salts

Correct Answer: Enhance solubility of actives while maintaining skin hydration

Q44. Which storage condition is best to maintain glycerol quality in pharmaceutical stock?

• Cool, dry, well-sealed container protected from contaminants
• Open container at high temperature and humidity
• Exposed to direct sunlight in a plastic drum
• Mixed with reactive acids for long-term stability

Correct Answer: Cool, dry, well-sealed container protected from contaminants

Q45. Which physiological effect is associated with topical glycerol application?

• Improved skin hydration and increased plasticity of stratum corneum
• Persistent systemic hypotension
• Permanent alteration of DNA in epidermis
• Complete occlusion of sweat glands

Correct Answer: Improved skin hydration and increased plasticity of stratum corneum

Q46. Which chromatographic technique is often used to separate glycerol from other low molecular weight glycols?

• Gas chromatography (GC) with appropriate derivatization or LC with RI/ELSD
• Paper chromatography only
• Size-exclusion chromatography for volatile organics
• Ion-exchange chromatography for neutral molecules

Correct Answer: Gas chromatography (GC) with appropriate derivatization or LC with RI/ELSD

Q47. Which statement about glycerol in pediatric formulations is correct?

• Concentrations must be controlled due to osmolarity and calorie considerations
• Glycerol is contraindicated in all pediatric uses
• Glycerol has no caloric value and is inert
• High glycerol formulations are preferred for neonates

Correct Answer: Concentrations must be controlled due to osmolarity and calorie considerations

Q48. Which chemical class do glyceryl esters (e.g., glyceryl monooleate) belong to that is important for drug delivery?

• Amphiphilic lipids that can form liquid crystals and self-assemblies
• Strong acids neutralizing actives
• Hydrophilic polymers only
• Inorganic salts

Correct Answer: Amphiphilic lipids that can form liquid crystals and self-assemblies

Q49. Which manufacturing impurity in crude glycerol is of greatest toxicological concern?

• Diethylene glycol contamination
• Sodium chloride residues
• Cellulose fibers
• Natural flavoring agents

Correct Answer: Diethylene glycol contamination

Q50. A formulation scientist chooses glycerol over water-soluble solvents primarily because:

• It increases viscosity, stabilizes formulations and provides humectancy while offering solvent capacity
• It is cheaper than water in all cases
• It evaporates rapidly to leave a film
• It acts as a primary preservative against all microbes

Correct Answer: It increases viscosity, stabilizes formulations and provides humectancy while offering solvent capacity

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