Reactions of fatty acids MCQs With Answer — This concise introduction covers key chemical and biochemical reactions of fatty acids essential for B. Pharm students. Learn reaction types such as esterification, saponification, hydrogenation, oxidation, epoxidation, transesterification, decarboxylation, and enzymatic beta-oxidation, plus their relevance in drug formulation, stability, and prodrug design. The content emphasizes reagents, mechanisms, conditions, and analytical conversions (e.g., methylation for GC), plus implications for rancidity and antioxidants. Clear, exam-focused MCQs with explanations will sharpen your understanding of lipid chemistry in pharmaceutics and metabolism. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which reagent is commonly used for the Fischer esterification of a fatty acid to form an alkyl ester?
- Hydrogen peroxide
- Sulfuric acid
- Sodium borohydride
- Pyridine
Correct Answer: Sulfuric acid
Q2. Saponification of triglycerides yields which two main products?
- Glycerol and free fatty acids
- Glycerol and fatty acid salts (soap)
- Acyl chlorides and glycerol
- Fatty acid methyl esters and water
Correct Answer: Glycerol and fatty acid salts (soap)
Q3. Hydrogenation of unsaturated fatty acids converts double bonds into what functional group?
- Alcohols
- Carbonyls
- Single carbon–carbon bonds (saturated)
- Epoxides
Correct Answer: Single carbon–carbon bonds (saturated)
Q4. Which catalyst is typically used for catalytic hydrogenation of fatty acids?
- Pd/C
- AlCl3
- LiAlH4
- KMnO4
Correct Answer: Pd/C
Q5. Transesterification in biodiesel production commonly converts triglycerides into what molecules?
- Fatty acid amides
- Fatty alcohols
- Fatty acid methyl esters (FAMEs)
- Glyceraldehyde
Correct Answer: Fatty acid methyl esters (FAMEs)
Q6. Which base is commonly used for base-catalyzed transesterification to produce biodiesel?
- HCl
- NaOH
- ZnCl2
- AgNO3
Correct Answer: NaOH
Q7. Formation of an acyl chloride from a fatty acid is typically done using which reagent?
- SOCl2 (thionyl chloride)
- NaBH4
- PCC
- mCPBA
Correct Answer: SOCl2 (thionyl chloride)
Q8. Which reaction converts a fatty acid to a fatty acid methyl ester for GC analysis?
- Fischer esterification with methanol
- Hydrogenation
- Ozonolysis
- Kolbe electrolysis
Correct Answer: Fischer esterification with methanol
Q9. Which oxidizing agent is commonly used for epoxidation of carbon–carbon double bonds in unsaturated fatty acids?
- mCPBA (meta-chloroperbenzoic acid)
- LiAlH4
- H2/Pd
- NaBH4
Correct Answer: mCPBA (meta-chloroperbenzoic acid)
Q10. Ozonolysis of unsaturated fatty acids cleaves C=C bonds to yield which types of products?
- Epoxides and alcohols
- Aldehydes and/or carboxylic acids
- Alkanes only
- Amides
Correct Answer: Aldehydes and/or carboxylic acids
Q11. Lipid peroxidation leading to rancidity in formulations primarily involves which species?
- Free radicals and peroxides
- Hydrides
- Carbocations
- Carbanions
Correct Answer: Free radicals and peroxides
Q12. Which antioxidant is commonly used to prevent oxidative rancidity of fatty acids in pharmaceutical formulations?
- Vitamin C (ascorbic acid)
- BHT (butylated hydroxytoluene)
- H2O2
- NaCl
Correct Answer: BHT (butylated hydroxytoluene)
Q13. The Kolbe electrolysis of carboxylate salts of fatty acids yields what product type?
- Alkenes
- Long-chain hydrocarbons (alkanes) via radical coupling
- Carboxylic acids with shorter chains
- Esters
Correct Answer: Long-chain hydrocarbons (alkanes) via radical coupling
Q14. Amidation of fatty acids to form fatty acid amides typically requires activation of the acid as what intermediate?
- Acyl radical
- Acyl chloride or activated ester
- Carbanion
- Epoxide
Correct Answer: Acyl chloride or activated ester
Q15. Which coupling reagent is commonly used for amidation of fatty acids with amines in mild conditions?
- PCC
- DCC (dicyclohexylcarbodiimide)
- LiAlH4
- KMnO4
Correct Answer: DCC (dicyclohexylcarbodiimide)
Q16. Steglich esterification uses DCC and which catalyst to form esters under mild conditions?
- DMAP (4-dimethylaminopyridine)
- H2SO4
- NaOH
- AlCl3
Correct Answer: DMAP (4-dimethylaminopyridine)
Q17. Which test qualitatively detects unsaturation (double bonds) in fatty acids?
- Silver nitrate test
- Bromine water decolorization
- Tollens’ test
- Seliwanoff’s test
Correct Answer: Bromine water decolorization
Q18. Partial hydrogenation of vegetable oils can produce which undesired isomer relevant to health?
- Trans fatty acids
- Branched-chain fatty acids
- Short-chain fatty acids
- Glycolipids
Correct Answer: Trans fatty acids
Q19. Which enzymatic process breaks down fatty acids two carbons at a time in mitochondria?
- Glycolysis
- Beta-oxidation
- Alpha-oxidation
- Omega-oxidation
Correct Answer: Beta-oxidation
Q20. The first enzymatic step of mitochondrial beta-oxidation is catalyzed by which enzyme class?
- Acyl-CoA dehydrogenase
- Hydratase
- Thiolase
- Carboxylase
Correct Answer: Acyl-CoA dehydrogenase
Q21. Which reaction forms triglycerides in biological systems?
- Transesterification of phospholipids
- Esterification of glycerol with fatty acyl-CoA
- Oxidative cleavage of glycerol
- Hydrogenation of glycerol
Correct Answer: Esterification of glycerol with fatty acyl-CoA
Q22. Fatty acid methyl esters are commonly analyzed by which technique in quality control?
- UV-Vis spectroscopy
- Gas chromatography (GC)
- Polarimetry
- Flame photometry
Correct Answer: Gas chromatography (GC)
Q23. Which reagent converts a fatty acid to its methyl ester using acidic catalysis for GC analysis?
- BF3-methanol complex
- NaBH4 in methanol
- LiAlH4 in ether
- mCPBA
Correct Answer: BF3-methanol complex
Q24. In pharmaceutical prodrug design, fatty acid esterification of drugs often increases what property?
- Water solubility
- Lipophilicity and membrane permeability
- Ionization at physiological pH
- Covalent binding to proteins
Correct Answer: Lipophilicity and membrane permeability
Q25. Hydrolysis of an ester under basic conditions is called:
- Saponification
- Hydration
- Hydrogenation
- Transamination
Correct Answer: Saponification
Q26. Which catalyst promotes hydration of a double bond in fatty acids to form alcohols (in some synthetic routes)?
- Hg(OAc)2 (oxymercuration)
- NaBH4
- KMnO4
- PCC
Correct Answer: Hg(OAc)2 (oxymercuration)
Q27. Which reaction on unsaturated fatty acids can lead to formation of hydroxy fatty acids useful in cosmetics?
- Epoxide opening (hydrolysis)
- Decarboxylation
- Kolbe electrolysis
- Amidation
Correct Answer: Epoxide opening (hydrolysis)
Q28. Which process yields conjugated dienes in polyunsaturated fatty acids during oxidative degradation?
- Lipid peroxidation
- Transesterification
- Saponification
- Hydrogenation
Correct Answer: Lipid peroxidation
Q29. Which reagent is used for converting fatty acids into long-chain acyl chlorides for further acylation?
- PCl5 or SOCl2
- NaHCO3
- NaBH4
- H2O2
Correct Answer: PCl5 or SOCl2
Q30. The formation of glyceryl esters (mono-, di-, triacylglycerols) often uses which type of catalyst industrially?
- Acid catalysts (e.g., H2SO4)
- Strong bases only
- Nonpolar solvents without catalyst
- Radical initiators
Correct Answer: Acid catalysts (e.g., H2SO4)
Q31. Which analytical change indicates fatty acid oxidation in a formulation?
- Decrease in peroxide value
- Increase in peroxide value and TBARS
- Drop in pH to neutral
- Increase in refractive index only
Correct Answer: Increase in peroxide value and TBARS
Q32. Amide derivatives of fatty acids can act as which type of pharmacologically active molecules?
- Local anesthetics only
- Bioactive signaling lipids (e.g., endocannabinoid analogs)
- Only inert excipients
- Only preservatives
Correct Answer: Bioactive signaling lipids (e.g., endocannabinoid analogs)
Q33. Which reaction would you use to shorten a fatty acid chain by one carbon?
- Beta-oxidation (enzymatic decarboxylation gives two-carbon units)
- Kolbe electrolysis
- Ozonolysis to completely remove one carbon
- Fischer esterification
Correct Answer: Beta-oxidation (enzymatic decarboxylation gives two-carbon units)
Q34. Which method is used to isomerize cis double bonds to trans during industrial processing?
- Acid catalysis at high temperature
- Enzymatic hydrogenation
- Low-temperature freezing
- Hydrogenation without catalyst
Correct Answer: Acid catalysis at high temperature
Q35. Which reagent selectively reduces carboxylic acids to primary alcohols in fatty acid chemistry?
- NaBH4
- LiAlH4
- H2/Pd
- mCPBA
Correct Answer: LiAlH4
Q36. Synthesis of fatty acid chlorides followed by reaction with alcohols gives which class of compounds?
- Ketones
- Esters
- Amides
- Alkenes
Correct Answer: Esters
Q37. Which reaction mechanism is involved in base-catalyzed transesterification of triglycerides?
- Nucleophilic acyl substitution
- Electrophilic aromatic substitution
- Free radical polymerization
- Pericyclic rearrangement
Correct Answer: Nucleophilic acyl substitution
Q38. Which spectral change in IR indicates conversion of a fatty acid to an ester?
- Appearance of a strong C=O stretching band near 1700 cm-1 and C–O stretch near 1200 cm-1
- Loss of O–H stretch only
- Appearance of an N–H stretch
- Only a shift in fingerprint region
Correct Answer: Appearance of a strong C=O stretching band near 1700 cm-1 and C–O stretch near 1200 cm-1
Q39. Which oxidation state change occurs when a fatty acid is reduced to a primary alcohol?
- Carbon oxidation state increases
- Carbon oxidation state decreases
- No change in oxidation state
- Oxygen gains electrons only
Correct Answer: Carbon oxidation state decreases
Q40. Which reaction on a polyunsaturated fatty acid can produce epoxides used in polymer and surfactant chemistry?
- Epoxidation of double bonds
- Decarboxylation
- Saponification
- Hydrogenolysis
Correct Answer: Epoxidation of double bonds
Q41. Which enzyme class catalyzes hydrolysis of triglycerides in the digestive tract?
- Proteases
- Lipases
- Amylases
- Oxidases
Correct Answer: Lipases
Q42. Conjugated linoleic acid formation involves which chemical change in unsaturated fats?
- Shift and conjugation of double bonds (isomerization)
- Chain elongation by two carbons
- Removal of carboxyl group
- Complete saturation
Correct Answer: Shift and conjugation of double bonds (isomerization)
Q43. Which reagent is used to convert a fatty acid to its corresponding acid anhydride?
- Acetic anhydride with coupling agents
- NaOH
- H2
- mCPBA
Correct Answer: Acetic anhydride with coupling agents
Q44. In fatty acid chemistry, protecting groups are sometimes used for which purpose?
- To prevent unwanted reactions at functional groups during multistep synthesis
- To increase acidity of the carboxyl group
- To catalyze oxidation
- To polymerize fatty acids
Correct Answer: To prevent unwanted reactions at functional groups during multistep synthesis
Q45. Which method is suitable to determine double bond position in fatty acids?
- Mass spectrometry of derivatized methyl esters (e.g., DMDS adducts)
- Simple boiling point measurement
- Colorimetric pH test
- Thin layer chromatography without derivatization
Correct Answer: Mass spectrometry of derivatized methyl esters (e.g., DMDS adducts)
Q46. Which of the following is a common industrial method to hydrogenate fatty acids selectively to avoid over-reduction?
- Use of Lindlar catalyst for partial hydrogenation
- Use of strong oxidants
- High-temperature radical hydrogenation
- Electrochemical oxidation
Correct Answer: Use of Lindlar catalyst for partial hydrogenation
Q47. Which reaction converts free fatty acids to water-soluble salts increasing removal from formulations?
- Neutralization with base to form soap
- Hydrogenation
- Epoxidation
- Methylation
Correct Answer: Neutralization with base to form soap
Q48. Which transformation is typically used to activate fatty acids for peptide coupling or conjugation?
- Formation of acyl chloride or active ester (e.g., NHS ester)
- Reduction to alcohol
- Hydrogenation of double bonds
- Thermal decarboxylation
Correct Answer: Formation of acyl chloride or active ester (e.g., NHS ester)
Q49. Which condition accelerates autoxidation of fatty acids in stored formulations?
- Low temperature and absence of oxygen
- Presence of light, heat, and metal catalysts (e.g., iron)
- Use of antioxidants
- Anaerobic storage
Correct Answer: Presence of light, heat, and metal catalysts (e.g., iron)
Q50. Which chemical change converts an unsaturated fatty acid into two shorter-chain carboxylic acids?
- Epoxidation
- Ozonolysis followed by oxidative workup
- Hydrogenation
- Saponification
Correct Answer: Ozonolysis followed by oxidative workup
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