Structure and uses of chloroform MCQs With Answer

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Introduction: Chloroform (CHCl3) is a fundamental organic solvent and reagent encountered frequently in B. Pharm courses, particularly in pharmaceutical chemistry and pharmacology. Understanding the structure and uses of chloroform — including its molecular geometry, physical properties, synthesis routes, analytical signatures, pharmacological history as an anesthetic, and toxic metabolic pathways — is essential for safe laboratory practice and drug research. Key topics include haloform reactions, the Reimer–Tiemann formylation, solvent selection, metabolism to trichloromethyl radicals and phosgene, and occupational safety limits. This collection of targeted MCQs will reinforce core concepts, analytical interpretation, and safety considerations for B. Pharm students. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the molecular formula of chloroform?

  • CH4
  • CHCl3
  • CCl4
  • CH2Cl2

Correct Answer: CHCl3

Q2. What is the approximate molecular weight of chloroform?

  • 84.93 g/mol
  • 119.38 g/mol
  • 153.82 g/mol
  • 77.15 g/mol

Correct Answer: 119.38 g/mol

Q3. Which hybridization does the central carbon in chloroform exhibit?

  • sp
  • sp2
  • sp3
  • dsp2

Correct Answer: sp3

Q4. What is the molecular geometry around the carbon atom in chloroform?

  • Trigonal planar
  • Tetrahedral
  • Linear
  • Bent

Correct Answer: Tetrahedral

Q5. Which statement accurately describes chloroform’s polarity?

  • Nonpolar molecule with zero dipole moment
  • Polar molecule due to unequal C–Cl bond distribution
  • Highly ionic
  • Amphiprotic solvent

Correct Answer: Polar molecule due to unequal C–Cl bond distribution

Q6. What is the approximate dipole moment of chloroform?

  • 0 D
  • 1.04 D
  • 3.9 D
  • 6.0 D

Correct Answer: 1.04 D

Q7. Which intermolecular forces are most significant in chloroform?

  • Hydrogen bonding only
  • London dispersion and dipole–dipole interactions
  • Ionic interactions
  • Covalent network bonding

Correct Answer: London dispersion and dipole–dipole interactions

Q8. What is the normal boiling point of chloroform?

  • 173 °C
  • 20 °C
  • 61.2 °C
  • -33 °C

Correct Answer: 61.2 °C

Q9. How does chloroform behave relative to water in terms of density?

  • Less dense than water and floats
  • Approximately same density as water
  • More dense than water and sinks
  • Forms azeotrope with water that is lighter

Correct Answer: More dense than water and sinks

Q10. Which industrial method primarily produces chloroform?

  • Hydration of acetylene
  • Fractional chlorination of methane
  • Fischer–Tropsch synthesis
  • Steam cracking of naphtha

Correct Answer: Fractional chlorination of methane

Q11. Which laboratory reaction is commonly used to prepare chloroform from ethanol or acetone?

  • Wurtz reaction
  • Haloform reaction with hypochlorite
  • Grignard reaction
  • Friedel–Crafts acylation

Correct Answer: Haloform reaction with hypochlorite

Q12. Which reagent combination in organic synthesis commonly generates dichlorocarbene using chloroform?

  • Chloroform + base (e.g., NaOH) in Reimer–Tiemann
  • Chloroform + HCl
  • Chloroform + Pd/C hydrogenation
  • Chloroform + ozone

Correct Answer: Chloroform + base (e.g., NaOH) in Reimer–Tiemann

Q13. The Reimer–Tiemann reaction using chloroform is primarily used to achieve which transformation?

  • Ortho-formylation of phenols
  • Nitration of benzene
  • Hydrogenation of alkenes
  • Carboxylation of alkanes

Correct Answer: Ortho-formylation of phenols

Q14. Which metabolite or reactive species is primarily implicated in chloroform-induced hepatotoxicity?

  • Trichloromethyl radical (•CCl3) leading to phosgene
  • Carbon monoxide (CO)
  • Chlorine gas (Cl2) directly
  • Hydroxyl radical only

Correct Answer: Trichloromethyl radical (•CCl3) leading to phosgene

Q15. Which enzyme system metabolizes chloroform to reactive species in the liver?

  • CYP450 monooxygenases
  • Alcohol dehydrogenase only
  • Glutathione peroxidase
  • Peptidyl transferase

Correct Answer: CYP450 monooxygenases

Q16. Historically, chloroform was used as a general anesthetic. What major adverse cardiac effect led to its decline in medical use?

  • Severe hypertension
  • Ventricular arrhythmias and sudden cardiac depression
  • Increased intracranial pressure exclusively
  • Excessive salivation

Correct Answer: Ventricular arrhythmias and sudden cardiac depression

Q17. In analytical chemistry, the characteristic 1H NMR chemical shift for residual CHCl3 in CDCl3 is approximately:

  • 0.00 ppm
  • 1.25 ppm
  • 7.26 ppm
  • 9.50 ppm

Correct Answer: 7.26 ppm

Q18. Which IR spectral region is most indicative of C–H stretching in chloroform?

  • 4000–3000 cm−1 around 3000 cm−1
  • 2000–1500 cm−1
  • 1000–600 cm−1 only
  • Below 400 cm−1

Correct Answer: 4000–3000 cm−1 around 3000 cm−1

Q19. Which property makes chloroform a commonly used solvent in pharmaceutical extraction and formulation research?

  • High polarity and water miscibility
  • Low boiling point and ability to dissolve many organics
  • Strong acidic behavior
  • Biodegradability and nutritive value

Correct Answer: Low boiling point and ability to dissolve many organics

Q20. What safety practice is essential when storing chloroform in the lab?

  • Store in open containers at sunlight-exposed bench
  • Store in dark, tightly closed glass containers away from heat
  • Store with strong bases to neutralize
  • Store under direct UV to prevent decomposition

Correct Answer: Store in dark, tightly closed glass containers away from heat

Q21. Chloroform reacts with strong bases to produce which hazardous species if not controlled?

  • Methane gas
  • Dichlorocarbene and potentially phosgene under oxidative conditions
  • Sodium chloride precipitate only
  • Ethylene glycol

Correct Answer: Dichlorocarbene and potentially phosgene under oxidative conditions

Q22. In the haloform reaction, which functional group substrate commonly yields chloroform when halogenated fully at the methyl group?

  • Tertiary alcohols only
  • Methyl ketones (e.g., acetone)
  • Alkenes exclusively
  • Carboxylic acids

Correct Answer: Methyl ketones (e.g., acetone)

Q23. Why is chloroform less favorable as a solvent for biological assays involving enzymes?

  • It strongly stabilizes enzymes, giving false positives
  • It denatures proteins and is immiscible with aqueous buffers
  • It enhances enzyme activity nonspecifically
  • It is too polar for enzyme assays

Correct Answer: It denatures proteins and is immiscible with aqueous buffers

Q24. Which route of exposure to chloroform poses the highest immediate risk in the laboratory?

  • Ingestion of large volumes
  • Inhalation of concentrated vapors in a poorly ventilated area
  • Brief skin contact with dilute splashes
  • Eye exposure to trace amounts

Correct Answer: Inhalation of concentrated vapors in a poorly ventilated area

Q25. Occupational safety guidelines classify chloroform as which of the following for carcinogenic potential?

  • Not classifiable and completely safe
  • Probable/possible human carcinogen (IARC group 2B historically; some classifications vary)
  • Non-carcinogenic and food additive
  • Definitive human carcinogen (IARC group 1)

Correct Answer: Probable/possible human carcinogen (IARC group 2B historically; some classifications vary)

Q26. What is the melting point of chloroform approximately?

  • 0 °C
  • -63.5 °C
  • 25 °C
  • 100 °C

Correct Answer: -63.5 °C

Q27. Chloroform can generate phosgene under which conditions?

  • Exposure to strong reducing agents only
  • Oxidative conditions at high temperature or in the presence of oxygen and UV
  • When mixed with alcohols at room temperature
  • Only when exposed to acids below pH 1

Correct Answer: Oxidative conditions at high temperature or in the presence of oxygen and UV

Q28. In thin-layer chromatography (TLC), chloroform is commonly used as:

  • A stationary phase
  • A mobile phase solvent or component of a solvent system
  • A visualization reagent only
  • An adsorbent on the plate

Correct Answer: A mobile phase solvent or component of a solvent system

Q29. Which of the following best describes chloroform’s solubility in water?

  • Miscible with water in all proportions
  • Sparingly soluble (~8 g/L at 20 °C)
  • Completely insoluble
  • Forms a stable emulsion with water

Correct Answer: Sparingly soluble (~8 g/L at 20 °C)

Q30. Which laboratory method is commonly used to remove chloroform residues from organic extracts before analysis?

  • Vacuum evaporation / rotary evaporation under reduced pressure
  • Simple heating to 200 °C
  • Adding concentrated acid to neutralize
  • Direct injection without removal

Correct Answer: Vacuum evaporation / rotary evaporation under reduced pressure

Q31. Which reagent combination is used in the classical haloform test that produces a yellow precipitate for methyl ketones (and can produce chloroform when exhaustive chlorination occurs)?

  • PCl5 and benzene
  • NaOCl (bleach) and NaOH
  • LiAlH4 in ether
  • Conc. H2SO4 and KMnO4

Correct Answer: NaOCl (bleach) and NaOH

Q32. Which pharmacological or toxicological effect is directly linked to chloroform’s metabolite phosgene?

  • Renal filtration enhancement
  • Protein acylation leading to liver cell necrosis
  • Vitamin K activation
  • Enhanced neurotransmitter release beneficial to cognition

Correct Answer: Protein acylation leading to liver cell necrosis

Q33. For chromatographic analysis, why is chloroform sometimes avoided despite its solvent properties?

  • It reacts with silica to permanently deactivate plates
  • Its toxicity, formation of artifacts, and UV cutoff can interfere with sensitive detectors
  • It is too polar for any organic solute
  • It turbulently expands columns causing damage

Correct Answer: Its toxicity, formation of artifacts, and UV cutoff can interfere with sensitive detectors

Q34. Which storage precaution minimizes chloroform’s decomposition to acidic byproducts?

  • Store near strong oxidizers
  • Add stabilizers such as ethanol or amylene and store in amber bottles
  • Expose to sunlight periodically
  • Keep in metal containers that catalyze decomposition

Correct Answer: Add stabilizers such as ethanol or amylene and store in amber bottles

Q35. Which statement about chloroform’s flammability is correct?

  • Highly flammable like diethyl ether
  • Generally non-flammable under normal conditions but can decompose and form flammable or toxic products
  • Explodes spontaneously on contact with glass
  • Must be refrigerated at -80 °C to remain non-flammable

Correct Answer: Generally non-flammable under normal conditions but can decompose and form flammable or toxic products

Q36. Which analytical technique can quantify trace chloroform in water samples for environmental monitoring?

  • Gas chromatography with electron capture or mass spectrometric detection (GC-ECD/GC-MS)
  • Polarimetry
  • UV-visible spectrophotometry at 800 nm
  • Thin-layer chromatography only

Correct Answer: Gas chromatography with electron capture or mass spectrometric detection (GC-ECD/GC-MS)

Q37. In medicinal chemistry labs, chloroform is often replaced by alternative solvents. Which solvent is a common replacement for nonpolar organic extractions with lower toxicity?

  • Carbon tetrachloride (CCl4)
  • Ethyl acetate or dichloromethane depending on polarity needs
  • Methanol for nonpolar compounds
  • Concentrated hydrochloric acid

Correct Answer: Ethyl acetate or dichloromethane depending on polarity needs

Q38. What precaution is important when performing a Reimer–Tiemann reaction with chloroform?

  • Use excess strong acid to suppress carbene formation
  • Control temperature and use proper ventilation due to dichlorocarbene and phosgene risks
  • Perform reaction in an open flame to drive off gases
  • Never use phenolic substrates

Correct Answer: Control temperature and use proper ventilation due to dichlorocarbene and phosgene risks

Q39. Which of the following best explains why chloroform is a good solvent for lipophilic drug extraction?

  • High dielectric constant similar to water
  • Ability to solubilize nonpolar organic molecules due to its moderate polarity and good solvating power for lipophiles
  • Ability to form micelles
  • It reacts covalently with drugs to increase solubility

Correct Answer: Ability to solubilize nonpolar organic molecules due to its moderate polarity and good solvating power for lipophiles

Q40. Which chemical hazard is of greatest concern if chloroform is heated strongly in presence of oxygen or UV light?

  • Formation of hydrogen gas
  • Formation of phosgene (COCl2)
  • Reduction to methane
  • Conversion to ethanol

Correct Answer: Formation of phosgene (COCl2)

Q41. In a lab spill, what is the recommended immediate action for chloroform liquid spills on the bench?

  • Wipe with bare hands and dispose in the sink
  • Evaporate by heating with Bunsen burner
  • Absorb with inert material, ventilate area, and follow hazardous waste disposal
  • Neutralize with strong acid

Correct Answer: Absorb with inert material, ventilate area, and follow hazardous waste disposal

Q42. Which physical property explains why chloroform is useful in liquid–liquid extraction to separate organic compounds from aqueous solutions?

  • High miscibility with water
  • Density greater than water and immiscibility, allowing phase separation
  • It polymerizes on contact with water
  • It forms covalent complexes with salts

Correct Answer: Density greater than water and immiscibility, allowing phase separation

Q43. Which pharmacological classification best describes chloroform’s former clinical role?

  • Local anesthetic
  • General anesthetic (historical use)
  • Antibiotic
  • Antihypertensive agent

Correct Answer: General anesthetic (historical use)

Q44. Which occupational control is most effective at preventing inhalation exposure to chloroform vapors?

  • Local exhaust ventilation and fume hoods
  • Wearing cotton lab coats only
  • Using open benches with no ventilation
  • Storing containers on lab floor

Correct Answer: Local exhaust ventilation and fume hoods

Q45. Why must chloroform be tested for stability before storage for prolonged periods?

  • Because it polymerizes into solid plastic
  • Because it can form acidic and toxic decomposition products like phosgene and HCl if degraded
  • Because it rapidly becomes nonvolatile
  • Because it converts into methanol spontaneously

Correct Answer: Because it can form acidic and toxic decomposition products like phosgene and HCl if degraded

Q46. Which analytical impurity in chloroform is commonly removed by passing through activated alumina prior to GC analysis?

  • Water only
  • Stabilizer residues and acidic decomposition products
  • Solid salts like NaCl
  • Metal particles

Correct Answer: Stabilizer residues and acidic decomposition products

Q47. What color change or physical sign indicates spontaneous degradation of stored chloroform?

  • Becomes colorless and odorless
  • Turned yellowish to brown and develops an acidic odor
  • Solidifies into white crystals
  • Turns bright blue

Correct Answer: Turned yellowish to brown and develops an acidic odor

Q48. In veterinary or historical human anesthesia, why was chloroform largely replaced by safer agents?

  • Because it produced inadequate analgesia
  • Because of high incidence of cardiac and hepatic toxicity and unpredictable dosing
  • Because it was too inexpensive
  • Because it had a sweet taste

Correct Answer: Because of high incidence of cardiac and hepatic toxicity and unpredictable dosing

Q49. Which solvent parameter (Kamlet–Taft or polarity index) attribute of chloroform is relevant for solubility prediction in drug formulation?

  • High hydrogen-bond donating ability only
  • Moderate polarity/polarizability and low hydrogen-bonding capability
  • High protic solvent index
  • Complete ionic character

Correct Answer: Moderate polarity/polarizability and low hydrogen-bonding capability

Q50. Which emergency medical effect should be monitored in acute chloroform inhalation poisoning?

  • Rapid improvement in consciousness without intervention
  • Respiratory depression, arrhythmias, and hepatic dysfunction
  • Immediate development of rash only
  • Marked hypoglycemia as sole effect

Correct Answer: Respiratory depression, arrhythmias, and hepatic dysfunction

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