Structure and uses of iodoform MCQs With Answer

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Structure and uses of iodoform MCQs With Answer — This concise, Student-friendly post helps B.Pharm students master the chemistry and pharmaceutical relevance of iodoform (CHI3). Learn the molecular structure, tetrahedral geometry, physical properties, common preparations (haloform reaction with I2/NaOH), diagnostic iodoform test for methyl ketones and ethanol, and pharmaceutical applications such as historic antiseptic use and wound dressings. Coverage includes reaction mechanisms, safety considerations, solubility and spectral clues relevant for formulation and analysis. Ideal for exam prep, lab practicals and pharmacognosy context, the content emphasizes both theoretical detail and applied pharmacy significance. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the molecular formula of iodoform?

  • CHI3
  • CI3H
  • CH3I
  • CIH3

Correct Answer: CHI3

Q2. What is the geometry around the central carbon in iodoform?

  • Tetrahedral
  • Trigonal planar
  • Linear
  • Bent

Correct Answer: Tetrahedral

Q3. Which reaction is commonly used to prepare iodoform in the laboratory?

  • Haloform reaction of methyl ketones with iodine and base
  • Friedel-Crafts acylation
  • Sandmeyer reaction
  • Wurtz coupling

Correct Answer: Haloform reaction of methyl ketones with iodine and base

Q4. Which starting materials give a positive iodoform test?

  • Methyl ketones and ethanol
  • Tertiary alcohols without a methyl group
  • Aldehydes without an α-methyl group
  • Alkanes

Correct Answer: Methyl ketones and ethanol

Q5. What is the appearance of iodoform as isolated solid?

  • Pale yellow crystalline solid
  • Colorless liquid
  • Dark brown powder
  • White amorphous solid

Correct Answer: Pale yellow crystalline solid

Q6. Which reagent supplies the halogen in the haloform preparation of iodoform?

  • Iodine (I2)
  • Chlorine gas (Cl2)
  • Bromine water (Br2)
  • Sodium iodide (NaI) alone

Correct Answer: Iodine (I2)

Q7. What is the main role of NaOH in the haloform reaction to form iodoform?

  • Provide hydroxide for deprotonation and hydrolysis
  • Act as a reducing agent
  • Complex with iodine to form iodate
  • Serve as a phase-transfer catalyst only

Correct Answer: Provide hydroxide for deprotonation and hydrolysis

Q8. During the haloform reaction that gives iodoform from acetone, what organic product accompanies iodoform formation?

  • Acetate ion (carboxylate)
  • Ethanol
  • Chloroform
  • Acrolein

Correct Answer: Acetate ion (carboxylate)

Q9. Which functional group in a molecule is directly responsible for a positive iodoform test?

  • CH3CO- (methyl carbonyl adjacent group)
  • Primary amine
  • Phenolic OH
  • Ether linkage

Correct Answer: CH3CO- (methyl carbonyl adjacent group)

Q10. Why is iodoform precipitated during the iodoform test?

  • Because CHI3 is poorly soluble in aqueous base and crystallizes
  • Because it forms a volatile gas that escapes
  • Because it forms a soluble colored complex
  • Because it polymerizes into a polymer

Correct Answer: Because CHI3 is poorly soluble in aqueous base and crystallizes

Q11. Which of the following alcohols gives a positive iodoform test?

  • Isopropyl alcohol (2º alcohol with methyl on α-carbon)
  • n-Butyl alcohol
  • Benzyl alcohol
  • Tert-butanol

Correct Answer: Isopropyl alcohol (2º alcohol with methyl on α-carbon)

Q12. Which product forms after exhaustive iodination and base hydrolysis of methyl ketones, besides iodoform?

  • Carboxylate salt
  • Alcohol
  • Aldehyde
  • Alkane

Correct Answer: Carboxylate salt

Q13. What is a primary pharmaceutical use historically associated with iodoform?

  • Topical antiseptic and wound dressing agent
  • Systemic antibiotic for oral use
  • Antihypertensive agent
  • Oral analgesic

Correct Answer: Topical antiseptic and wound dressing agent

Q14. Which safety concern is most commonly associated with iodoform?

  • Persistent unpleasant odor and potential local irritation
  • Highly flammable vapor explosion risk
  • Carcinogenicity at low concentrations
  • Severe corrosivity to metals

Correct Answer: Persistent unpleasant odor and potential local irritation

Q15. In the haloform mechanism, what intermediate results from successive halogenations at the methyl group?

  • Trihalomethyl ketone (e.g., CBr3CO-R or C I3CO-R)
  • Epoxide intermediate
  • Diazonium salt
  • Enamine

Correct Answer: Trihalomethyl ketone (e.g., CBr3CO-R or C I3CO-R)

Q16. How does the electron-withdrawing effect of iodine atoms influence the acidic character of the methyl hydrogen in methyl ketones during iodoform formation?

  • Increases acidity, facilitating deprotonation
  • Decreases acidity, preventing reaction
  • Has no effect on acidity
  • Makes the hydrogen basic

Correct Answer: Increases acidity, facilitating deprotonation

Q17. Which solvent is iodoform most soluble in among the following?

  • Ether or ethanol
  • Water
  • Dilute NaOH solution
  • Salt water

Correct Answer: Ether or ethanol

Q18. What is the typical color of iodoform crystals observed in the iodoform test?

  • Pale yellow
  • Deep red
  • Colorless
  • Blue

Correct Answer: Pale yellow

Q19. Which one of these compounds will NOT give a positive iodoform test?

  • Acetaldehyde without α-methyl
  • Acetone
  • Isopropanol
  • Ethanol

Correct Answer: Acetaldehyde without α-methyl

Q20. Which analytical observation confirms iodoform formation in the lab?

  • Formation of a yellow crystalline precipitate having antiseptic odor
  • Evolution of a colorless bubble gas
  • Change to bright blue color in solution
  • Complete dissolution without residue

Correct Answer: Formation of a yellow crystalline precipitate having antiseptic odor

Q21. What happens to the trihalomethyl group in the final hydrolysis step of the haloform reaction?

  • It leaves as haloform (CHI3) after cleavage
  • It is reduced to methane
  • It rearranges to form an alcohol
  • It forms an epoxide

Correct Answer: It leaves as haloform (CHI3) after cleavage

Q22. Which of the following methyl ketones will give iodoform on treatment with I2/NaOH?

  • Acetophenone
  • Butanone without methyl adjacent to carbonyl
  • 2,4-Pentanedione (enolizable but not methyl ketone)
  • Benzaldehyde

Correct Answer: Acetophenone

Q23. In pharmaceutical formulations, why has the use of iodoform declined?

  • Odor, irritation and availability of better antiseptics
  • It is too inexpensive to produce
  • Lack of antimicrobial effect
  • It is highly water soluble

Correct Answer: Odor, irritation and availability of better antiseptics

Q24. What is a typical melting point of iodoform (approximate)?

  • About 119 °C
  • About -10 °C
  • About 0 °C
  • About 250 °C

Correct Answer: About 119 °C

Q25. Which spectral technique can readily identify the characteristic singlet of the single proton in iodoform?

  • 1H NMR spectroscopy
  • IR spectroscopy only
  • Mass spectrometry only
  • UV-Vis spectroscopy

Correct Answer: 1H NMR spectroscopy

Q26. Which ion is generated in the base-catalyzed step that attacks iodine to form the halogenated intermediate?

  • Enolate ion
  • Carbocation
  • Hydride ion
  • Nitronate ion

Correct Answer: Enolate ion

Q27. Which of these is a correct balanced representation of the haloform reaction for acetone with iodine and base?

  • CH3COCH3 + 3 I2 + 4 OH- → CHI3 + CH3COO- + 3 I- + 3 H2O
  • CH3COCH3 + Cl2 → CHCl3 + acetic acid
  • CH3COCH3 + I2 → CHI3 only
  • CH3COCH3 + H2O → CHI3 + CO2

Correct Answer: CH3COCH3 + 3 I2 + 4 OH- → CHI3 + CH3COO- + 3 I- + 3 H2O

Q28. Which halogenated haloform is formed when chloroform test conditions are used with excess chlorine?

  • Chloroform (CHCl3)
  • Bromoform (CHBr3)
  • Iodoform (CHI3)
  • Fluoroform (CHF3)

Correct Answer: Chloroform (CHCl3)

Q29. Which structural feature in a steroidal or complex molecule might cause a false positive iodoform test?

  • An isolated methyl ketone (CH3CO-) moiety
  • Conjugated diene system
  • Quaternary ammonium salt
  • Ether linkage remote from carbonyl

Correct Answer: An isolated methyl ketone (CH3CO-) moiety

Q30. For B.Pharm students, why is understanding the iodoform test clinically relevant?

  • It aids identification of functional groups in drug analysis and characterization
  • It is directly used for systemic therapy
  • It determines melting point of drugs
  • It measures blood pressure

Correct Answer: It aids identification of functional groups in drug analysis and characterization

Q31. What type of odor does iodoform have that is clinically notable?

  • Characteristic medicinal and antiseptic odor
  • Sweet fruity odor
  • Odorless
  • Garlic-like odor

Correct Answer: Characteristic medicinal and antiseptic odor

Q32. In an organic synthesis lab, iodoform formation is sometimes used as a qualitative test for which synthetic intermediate?

  • Enolizable methyl ketone intermediate
  • Carbanion intermediate from non-enolizable ketones
  • Primary carbocation intermediate
  • Azide intermediate

Correct Answer: Enolizable methyl ketone intermediate

Q33. Which of the following is NOT a correct description of iodoform?

  • Highly soluble in water
  • Pale yellow crystalline solid
  • Contains three iodine atoms bonded to a single carbon
  • Used historically as topical antiseptic

Correct Answer: Highly soluble in water

Q34. Which laboratory precaution is important when performing the iodoform test?

  • Work in a well-ventilated area due to strong odor
  • Avoid light because iodoform is explosive in dark
  • Do not use base as it prevents the test
  • Heat strongly to favor iodoform formation

Correct Answer: Work in a well-ventilated area due to strong odor

Q35. Which atom on iodoform contributes most to its high molar mass and density?

  • Iodine atoms
  • Hydrogen atom
  • Carbon atom
  • Nitrogen atom (not present)

Correct Answer: Iodine atoms

Q36. What happens to the pH of the reaction mixture as the haloform reaction proceeds with excess base?

  • Remains basic due to excess OH-
  • Becomes strongly acidic
  • Becomes neutral immediately
  • Oscillates between acid and base

Correct Answer: Remains basic due to excess OH-

Q37. Which of these is an analytical drawback of using the iodoform test in complex drug mixtures?

  • Other functional groups may interfere and produce ambiguous results
  • It is too specific and never gives false positives
  • It quantifies concentration directly
  • It is colorless and impossible to observe

Correct Answer: Other functional groups may interfere and produce ambiguous results

Q38. In industrial settings, why might iodoform be converted to other iodine-containing compounds rather than used directly?

  • To produce more soluble or less odorous iodinated derivatives for application
  • Iodoform is too reactive for storage
  • Iodoform cannot be transported by road
  • Because conversion removes iodine atoms

Correct Answer: To produce more soluble or less odorous iodinated derivatives for application

Q39. Which reagent combination will fail to produce iodoform from acetone?

  • I2 with neutral water only (no base)
  • I2 with NaOH
  • Excess I2 with KOH
  • Iodine with aqueous hydroxide catalysts

Correct Answer: I2 with neutral water only (no base)

Q40. Which laboratory observation indicates completion of the haloform reaction producing iodoform?

  • Appearance of yellow precipitate and cessation of color change of iodine
  • Solution turns bright green and bubbles vigorously
  • Complete dissolution of all solids without precipitate
  • Formation of a black tarry residue only

Correct Answer: Appearance of yellow precipitate and cessation of color change of iodine

Q41. Which derivative of iodoform is directly responsible for its antiseptic activity?

  • Triiodomethyl group that releases iodine upon slow decomposition
  • Hydrogen atom alone
  • Carboxylate impurity
  • Alkyl chain on carbon

Correct Answer: Triiodomethyl group that releases iodine upon slow decomposition

Q42. What is the role of enolate formation in the haloform reaction?

  • It allows α-halogenation at the methyl group
  • It oxidizes the iodine to iodate
  • It forms a carbocation for substitution
  • It eliminates water to form an alkene

Correct Answer: It allows α-halogenation at the methyl group

Q43. Which statement best describes iodoform’s solubility in water?

  • Very low solubility in water
  • Highly soluble in water
  • Completely miscible with water
  • Instantly reacts with water to give acid

Correct Answer: Very low solubility in water

Q44. For drug analysis, which control test should accompany an iodoform test to confirm methyl ketone presence?

  • Complementary spectral analysis (IR/NMR) to confirm carbonyl and methyl signals
  • Only boiling point determination
  • Only tasting the compound
  • Ignition test for combustibility

Correct Answer: Complementary spectral analysis (IR/NMR) to confirm carbonyl and methyl signals

Q45. What is the main environmental concern when disposing of iodine-containing waste from the iodoform test?

  • Release of iodine and iodide into the environment which can be toxic to aquatic life
  • Formation of greenhouse gases
  • Radioactive contamination
  • None—iodine is inert

Correct Answer: Release of iodine and iodide into the environment which can be toxic to aquatic life

Q46. In a formulation context, why might iodoform be combined with bismuth subnitrate historically?

  • To create antiseptic dressings with reduced volatility and enhanced antimicrobial effect
  • To neutralize acids in oral tablets
  • To increase sweetness of oral syrups
  • To act as a primary solvent for injection

Correct Answer: To create antiseptic dressings with reduced volatility and enhanced antimicrobial effect

Q47. Which atom in iodoform is directly bonded to the hydrogen seen in its 1H NMR signal?

  • Carbon
  • Iodine
  • Oxygen
  • Nitrogen

Correct Answer: Carbon

Q48. What color change in the reaction mixture indicates iodine has been consumed during haloform formation?

  • Loss of brown color of iodine, becoming colorless or pale
  • Solution turns bright red
  • Solution fluoresces green under UV
  • Solution darkens to black immediately

Correct Answer: Loss of brown color of iodine, becoming colorless or pale

Q49. Which pharmacopoeial concern applies when using iodoform in wound care?

  • Potential for tissue irritation and residue requiring careful clinical justification
  • Risk of systemic hypoglycemia
  • High potential for drug interactions by P450 inhibition
  • Precipitation with saline to form harmful salts

Correct Answer: Potential for tissue irritation and residue requiring careful clinical justification

Q50. Which statement best summarizes the diagnostic value of the iodoform test for B.Pharm students?

  • It is a simple qualitative test for methyl ketones and certain alcohols, useful as a preliminary identification tool alongside spectroscopic methods
  • It is a definitive quantitative assay for drug purity
  • It detects all carbonyl-containing compounds universally
  • It replaces the need for NMR and IR analysis

Correct Answer: It is a simple qualitative test for methyl ketones and certain alcohols, useful as a preliminary identification tool alongside spectroscopic methods

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