Introduction: Succinic acid (IUPAC: butanedioic acid) is a saturated dicarboxylic acid with the formula C4H6O4 and important roles in both organic chemistry and pharmaceutical sciences. B. Pharm students should understand its structure, pKa values, physical properties, biochemical role in the Krebs cycle as succinate, formation of succinic anhydride and esters, industrial and bio-based production, and diverse pharmaceutical uses as a buffer, excipient, intermediate, and precursor for biodegradable polymers. This topic links medicinal chemistry, formulation science, and metabolic biochemistry, making it essential for drug development and formulation decisions. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which of the following is the IUPAC name of succinic acid?
- Butanedioic acid
- Propane-1,3-dioic acid
- Oxaloacetic acid
- Succinyl chloride
Correct Answer: Butanedioic acid
Q2. What is the molecular formula of succinic acid?
- C3H4O4
- C4H6O4
- C4H8O2
- C5H8O4
Correct Answer: C4H6O4
Q3. Which structural feature defines succinic acid?
- Aromatic ring with two carboxyl groups
- Saturated four-carbon chain with two terminal carboxyl groups
- Unsaturated dicarboxylic acid with a double bond
- Amino acid with carboxyl and amino groups
Correct Answer: Saturated four-carbon chain with two terminal carboxyl groups
Q4. Which is the correct condensed structural formula of succinic acid?
- HOOC-CH2-CH2-COOH
- HOOC-CH=CH-COOH
- HOOC-CH2-CH(OH)-COOH
- HOOC-CH2-CH3
Correct Answer: HOOC-CH2-CH2-COOH
Q5. What is a common industrial or biotechnological route for producing succinic acid for pharmaceutical use?
- Fermentation of sugars using engineered microbes
- Direct extraction from plant leaves
- Electrolysis of acetone
- Oxidation of benzene
Correct Answer: Fermentation of sugars using engineered microbes
Q6. Which of the following best describes succinic acid’s role in cellular metabolism?
- It inhibits glycolysis permanently
- It is an intermediate (succinate) in the Krebs cycle
- It is only involved in fatty acid synthesis
- It functions as a terminal electron acceptor in respiration
Correct Answer: It is an intermediate (succinate) in the Krebs cycle
Q7. Which enzyme catalyzes the oxidation of succinate to fumarate in the Krebs cycle?
- Succinyl-CoA synthetase
- Succinate dehydrogenase
- Fumarase
- Malate dehydrogenase
Correct Answer: Succinate dehydrogenase
Q8. Which of the following physical properties is typical for succinic acid?
- Colorless gas at room temperature
- White crystalline solid with relatively high melting point (~185 °C)
- Strongly volatile liquid with low boiling point
- Oil-like liquid immiscible with water
Correct Answer: White crystalline solid with relatively high melting point (~185 °C)
Q9. Succinic acid is classified chemically as which type of acid?
- Monocarboxylic acid
- Dicarboxylic acid
- Tricarboxylic acid
- Phenolic acid
Correct Answer: Dicarboxylic acid
Q10. What are the approximate pKa values of succinic acid (first and second dissociation)?
- pKa1 ~ 2.1, pKa2 ~ 3.4
- pKa1 ~ 4.2, pKa2 ~ 5.6
- pKa1 ~ 7.4, pKa2 ~ 9.2
- pKa1 ~ 1.0, pKa2 ~ 1.5
Correct Answer: pKa1 ~ 4.2, pKa2 ~ 5.6
Q11. Which succinic acid derivative is commonly formed by dehydration (loss of water) upon heating?
- Maleic acid
- Succinic anhydride
- Succinimide
- Butyric acid
Correct Answer: Succinic anhydride
Q12. Which type of reaction converts succinic acid into dimethyl succinate?
- Saponification
- Esterification (with methanol)
- Nitration
- Hydrogenation
Correct Answer: Esterification (with methanol)
Q13. Which pharmaceutical application commonly uses succinate salts?
- As a primary active pharmaceutical ingredient (API) for analgesia
- As buffering agents and pH modulators in formulations
- As intravenous anesthetics
- As opioid antagonists
Correct Answer: As buffering agents and pH modulators in formulations
Q14. What property of succinic acid makes it useful in forming biodegradable polymers like polybutylene succinate?
- Its aromaticity
- Its dicarboxylic functionality enabling ester linkages
- Its ability to act as a radical initiator
- Its metallic nature
Correct Answer: Its dicarboxylic functionality enabling ester linkages
Q15. Which of the following reactions reduces succinic acid to 1,4-butanediol?
- Oxidation with KMnO4
- Hydrogenation (catalytic hydrogenation)
- Halogenation with Br2
- Dehydration with H2SO4
Correct Answer: Hydrogenation (catalytic hydrogenation)
Q16. In formulation science, succinic acid can be used to adjust which parameter of a dosage form?
- Particle size distribution
- pH of aqueous systems
- Viscosity exclusively for gels
- Magnetic susceptibility
Correct Answer: pH of aqueous systems
Q17. Which salt form of succinic acid is frequently used in parenteral or oral formulations to improve solubility?
- Magnesium succinate
- Disodium succinate
- Calcium carbonate
- Potassium chloride
Correct Answer: Disodium succinate
Q18. Which analytical technique is most appropriate for confirming the presence of carboxyl groups in succinic acid?
- Infrared spectroscopy (IR)
- Flame photometry
- X-ray diffraction for amorphous solids only
- Polarimetry
Correct Answer: Infrared spectroscopy (IR)
Q19. What is the role of succinate in mitochondrial electron transport?
- Succinate directly donates electrons to complex I
- Succinate oxidation transfers electrons to complex II (succinate dehydrogenase), feeding ubiquinone
- Succinate reduces oxygen directly to water
- Succinate inhibits ATP synthase irrevocably
Correct Answer: Succinate oxidation transfers electrons to complex II (succinate dehydrogenase), feeding ubiquinone
Q20. Which of the following is a major advantage of bio-based succinic acid for pharmaceuticals?
- Higher toxicity compared to petrochemical succinic acid
- Lower purity suitable for APIs
- Sustainability and reduced carbon footprint
- Inability to form pharmaceutical salts
Correct Answer: Sustainability and reduced carbon footprint
Q21. Which reagent is commonly used to convert succinic acid to succinyl chloride (acid chloride)?
- Thionyl chloride (SOCl2)
- Sodium borohydride (NaBH4)
- Hydrochloric acid (dilute)
- Silver nitrate (AgNO3)
Correct Answer: Thionyl chloride (SOCl2)
Q22. Succinic acid’s two carboxyl groups behave how in terms of acidity?
- They have identical acidity and dissociate simultaneously
- They dissociate stepwise with two distinct pKa values
- They are non-ionizable under physiological pH
- They cannot form salts
Correct Answer: They dissociate stepwise with two distinct pKa values
Q23. In drug synthesis, succinic acid is often used as a linker to form which type of prodrug modification?
- Succinylation to form ester-linked prodrugs
- Nitration to form nitroprodrugs
- Halogenation to improve lipophilicity
- Direct conjugation to DNA
Correct Answer: Succinylation to form ester-linked prodrugs
Q24. Which property of succinic acid affects its partitioning and formulation behavior?
- High lipid solubility (log P > 4)
- Amphiprotic nature due to two ionizable carboxyl groups
- Nonpolar hydrocarbon chain with no ionizable groups
- Permanent cationic charge at physiological pH
Correct Answer: Amphiprotic nature due to two ionizable carboxyl groups
Q25. Which of the following is a common ester derivative used as a solvent or intermediate derived from succinic acid?
- Diethyl succinate
- Methyl salicylate
- Ethyl acetate
- Glycerol triacetate
Correct Answer: Diethyl succinate
Q26. What is the expected solubility behavior of succinic acid in water at neutral pH?
- Completely insoluble
- Partially soluble; ionized forms (succinate) increase solubility at neutral pH
- Highly volatile and evaporates
- Only soluble in nonpolar solvents
Correct Answer: Partially soluble; ionized forms (succinate) increase solubility at neutral pH
Q27. Which spectroscopic signal is most diagnostic for the carboxylic acid functional group in succinic acid?
- Strong broad O–H stretch around 2500–3300 cm−1 and C=O stretch near 1700 cm−1 in IR
- Sharp N–H stretch at 3300 cm−1 only
- Strong C≡C stretch at 2100 cm−1
- No distinctive IR bands for carboxyl
Correct Answer: Strong broad O–H stretch around 2500–3300 cm−1 and C=O stretch near 1700 cm−1 in IR
Q28. In pharmaceutical chemistry, succinic acid esters are often hydrolyzed in vivo by which class of enzymes?
- Oxidases
- Hydrolases/esterases
- Lyases
- Isomerases
Correct Answer: Hydrolases/esterases
Q29. Which of the following statements about succinic anhydride formation is correct?
- Succinic anhydride forms readily at room temperature without reagents
- Heating succinic acid can induce intramolecular dehydration to form succinic anhydride
- Succinic anhydride cannot be synthesized from succinic acid
- Formation of anhydride produces oxygen gas
Correct Answer: Heating succinic acid can induce intramolecular dehydration to form succinic anhydride
Q30. Which of the following safety/storage considerations is appropriate for pharmaceutical-grade succinic acid?
- Store in open containers at high humidity
- Keep in a cool, dry, well-closed container to avoid contamination and moisture uptake
- It must be stored under inert gas at −80 °C
- Store next to strong oxidizers without concern
Correct Answer: Keep in a cool, dry, well-closed container to avoid contamination and moisture uptake
Q31. Which reaction converts succinic acid into succinimide derivatives commonly used in organic synthesis?
- Reaction with ammonia or amines followed by dehydration
- Direct hydrogenation with Pd/C
- Radical polymerization
- Friedel–Crafts acylation
Correct Answer: Reaction with ammonia or amines followed by dehydration
Q32. Which of these is a pharmaceutical advantage of forming succinate salts of drugs?
- Always increases lipophilicity dramatically
- Can improve aqueous solubility and stability or modify release profiles
- Prevents any metabolism of the API
- Automatically converts drugs into prodrugs that cross the BBB
Correct Answer: Can improve aqueous solubility and stability or modify release profiles
Q33. Which carbon count and symmetry describe succinic acid?
- Three carbons, asymmetric
- Four carbons, symmetric across central C–C bond
- Five carbons, highly branched
- Four carbons, aromatic
Correct Answer: Four carbons, symmetric across central C–C bond
Q34. Which of the following is a downstream polymer application of succinic acid derivatives relevant to pharmaceutics?
- Polyethylene terephthalate for tablets
- Polybutylene succinate as biodegradable polymer for drug delivery
- Polystyrene for sterile packaging implants
- Polyvinyl chloride for active ingredient synthesis
Correct Answer: Polybutylene succinate as biodegradable polymer for drug delivery
Q35. Which reagent combination would most likely form an ester linkage between a drug molecule and succinic acid for prodrug formation?
- Carbodiimide coupling (e.g., EDC) or DCC with a catalytic DMAP
- Strong base only (NaOH) at cold temperature
- Pure water without catalysts
- Direct mixing at room temperature for 5 minutes
Correct Answer: Carbodiimide coupling (e.g., EDC) or DCC with a catalytic DMAP
Q36. How does succinic acid contribute to the taste profile when used in food/pharmaceutical flavoring?
- Provides a sweet taste exclusively
- Contributes a mild sour/acidic taste and can act as a flavor enhancer
- Acts as a bitter blocker only
- Has no taste at all
Correct Answer: Contributes a mild sour/acidic taste and can act as a flavor enhancer
Q37. Which analytical technique is best for determining the molecular weight of succinic acid and its esters?
- Mass spectrometry (MS)
- Ultraviolet-visible spectroscopy (UV-Vis)
- Polarimetry
- Paper chromatography only
Correct Answer: Mass spectrometry (MS)
Q38. Which functional group transformation is commonly used to make more reactive succinic acid derivatives for coupling reactions?
- Convert carboxyl to acid chloride (succinyl chloride)
- Convert to inert alkanes by hydrogenation
- Transform to aromatic ring via cyclization only
- Remove carboxyl groups completely
Correct Answer: Convert carboxyl to acid chloride (succinyl chloride)
Q39. In the context of drug metabolism, why might succinylated prodrugs be designed?
- To permanently block drug activity
- To improve water solubility and enable enzymatic cleavage to release active drug
- To render drugs completely non-bioavailable
- To increase volatility for inhalation
Correct Answer: To improve water solubility and enable enzymatic cleavage to release active drug
Q40. Which of the following best describes the environmental profile of bio-based succinic acid compared to petrochemical routes?
- Higher greenhouse gas emissions and energy use
- Lower carbon footprint and often more sustainable if produced via fermentation
- Always toxic to aquatic life in concentrated forms
- Indistinguishable in all metrics from petrochemical succinic acid
Correct Answer: Lower carbon footprint and often more sustainable if produced via fermentation
Q41. Which pharmaceutical excipient role can succinic acid serve due to its acidity and buffering capacity?
- Tablet binder only
- Buffering agent to maintain pH in liquid formulations
- Lubricant for tablet compression exclusively
- Antifoaming agent for suspensions
Correct Answer: Buffering agent to maintain pH in liquid formulations
Q42. Which structural isomer of succinic acid contains a trans double bond between C2 and C3?
- Fumaric acid
- Malic acid
- Maleic acid
- Oxalic acid
Correct Answer: Fumaric acid
Q43. Which reaction pathway converts succinic acid derivatives into monomers for biodegradable polyester synthesis?
- Polymerization of succinyl chloride without diol
- Condensation of dicarboxylic succinate derivatives with diols to form ester linkages
- Direct crystallization from aqueous solution
- Nitration followed by radical crosslinking
Correct Answer: Condensation of dicarboxylic succinate derivatives with diols to form ester linkages
Q44. Which of the following is true about succinic acid toxicity relevant to pharmaceutics?
- Highly toxic at trace levels and banned in formulations
- Generally low acute toxicity but dose and route dependent; handled per safety data sheets
- Non-toxic at any concentration
- Explosive when dry
Correct Answer: Generally low acute toxicity but dose and route dependent; handled per safety data sheets
Q45. What is the principal difference between maleic acid and succinic acid structurally?
- Maleic acid is aromatic while succinic acid is aliphatic
- Maleic acid is an unsaturated dicarboxylic acid (cis-alkene) while succinic acid is saturated
- Maleic acid has one carboxyl group; succinic has two
- They are identical compounds
Correct Answer: Maleic acid is an unsaturated dicarboxylic acid (cis-alkene) while succinic acid is saturated
Q46. Which one of the following laboratory transformations converts succinic acid to 4-carbon diol useful in polymer chemistry?
- Oxidation with PCC
- Complete hydrogenation/reduction to 1,4-butanediol
- Halogenation with chlorine only
- Carbonation with CO2
Correct Answer: Complete hydrogenation/reduction to 1,4-butanediol
Q47. Which of the following best explains why succinic acid can form internal anhydrides more readily than longer-chain dicarboxylic acids?
- Its chain length (four carbons) allows favorable five-membered ring formation upon dehydration
- Longer chains always form anhydrides more easily
- Because succinic acid is aromatic
- Due to its metallic bonds
Correct Answer: Its chain length (four carbons) allows favorable five-membered ring formation upon dehydration
Q48. In tablet formulation, succinic acid could be used to modify which property of a weakly basic drug?
- To increase crystallinity only
- To form a succinate salt, potentially improving aqueous solubility and dissolution
- To convert it to a volatile gas
- To render it insoluble at all pH values
Correct Answer: To form a succinate salt, potentially improving aqueous solubility and dissolution
Q49. Which reagent set would most likely be used to analyze succinic acid concentration quantitatively in solution in a pharmaceutical lab?
- Titration with a strong base (NaOH) using phenolphthalein or pH meter
- Weighing by hand without instrumentation
- Colorless reagent that gives no signal
- Measuring magnetic susceptibility
Correct Answer: Titration with a strong base (NaOH) using phenolphthalein or pH meter
Q50. For a B.Pharm student, which interdisciplinary topics are most relevant when studying succinic acid?
- Only organic synthesis, excluding metabolism and formulation
- Medicinal chemistry, biochemistry (Krebs cycle), formulation science, and polymer chemistry
- Only physical pharmacy without any chemical context
- Astrophysics and quantum mechanics exclusively
Correct Answer: Medicinal chemistry, biochemistry (Krebs cycle), formulation science, and polymer chemistry
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