Qualitative tests for alcohols MCQs With Answer

Qualitative tests for alcohols MCQs With Answer are essential for B. Pharm students to master identification and characterization of the alcohol functional group. This concise, topic-focused introduction explains common qualitative reactions—Lucas test, chromic acid oxidation, iodoform test, esterification and sodium metal reaction—highlighting expected observations, reagent details and distinctions between primary, secondary, tertiary and benzylic/allylic alcohols. Emphasis on mechanism, reagent composition and practical lab signs (color changes, precipitates, reaction times) helps students prepare for practical exams and viva voce. This resource is optimized for search terms relevant to practical pharmacognosy and organic analysis. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which of the following describes the composition of Lucas reagent used for distinguishing alcohols?

• A mixture of ZnCl2 in concentrated HCl
• A solution of CrO3 in acetic acid
• Neutral FeCl3 solution
• AgNO3 in NH3 (Tollens’ reagent)

Correct Answer: A mixture of ZnCl2 in concentrated HCl

Q2. In the Lucas test, a tertiary alcohol typically shows which observation?

• No reaction even after prolonged time
• Immediate formation of a cloudy or separate layer
• Slow reaction over several hours with slight turbidity
• Color change from orange to green

Correct Answer: Immediate formation of a cloudy or separate layer

Q3. Which qualitative test gives a yellow precipitate of iodoform for ethanol and methyl ketones?

• Iodoform test using I2/NaOH
• Lucas test using ZnCl2/HCl
• Ferric chloride test
• Jones oxidation

Correct Answer: Iodoform test using I2/NaOH

Q4. Chromic acid (Jones) oxidation gives a visible color change from orange to green when which type of alcohol is oxidized?

• Tertiary alcohols only
• Primary and secondary alcohols
• Aromatic alcohols exclusively
• No alcohols react with chromic acid

Correct Answer: Primary and secondary alcohols

Q5. Which reagent is preferred to oxidize primary alcohols to aldehydes without further oxidation to acids?

• PCC (pyridinium chlorochromate)
• Strong nitric acid
• Conc. sulfuric acid alone
• Potassium permanganate under vigorous heating

Correct Answer: PCC (pyridinium chlorochromate)

Q6. Which observation distinguishes a phenol from an alcohol using ferric chloride?

• No reaction for both phenol and alcohol
• Phenol gives a colored complex while alcohol gives no color
• Alcohol gives a colored complex while phenol gives no color
• Both give yellow precipitate with ferric chloride

Correct Answer: Phenol gives a colored complex while alcohol gives no color

Q7. Which alcohol will react fastest in the Lucas test?

• 1-Butanol (primary)
• 2-Butanol (secondary)
• tert-Butanol (tertiary)
• Benzyl alcohol (primary benzylic)

Correct Answer: tert-Butanol (tertiary)

Q8. Which of the following alcohols gives a positive iodoform test?

• tert-Butyl alcohol
• Isopropyl alcohol (2-propanol)
• 1-Butanol
• Benzyl alcohol

Correct Answer: Isopropyl alcohol (2-propanol)

Q9. Which reagent will oxidize a benzylic primary alcohol to a carboxylic acid under mild conditions?

• KMnO4 (potassium permanganate)
• Lucas reagent
• Tollens’ reagent
• Hydrogenation Pd/C

Correct Answer: KMnO4 (potassium permanganate)

Q10. The reaction of alcohol with sodium metal producing hydrogen gas indicates the presence of which functional group?

• Carbonyl group
• Alcohol (–OH) group
• Ether group
• Alkene group

Correct Answer: Alcohol (–OH) group

Q11. Which test differentiates primary from tertiary alcohol due to different rates of esterification with acetic anhydride?

• Observation of ester formation and ease of acetylation
• Formation of iodoform
• Reaction with Tollens’ reagent
• Reaction with bromine water

Correct Answer: Observation of ester formation and ease of acetylation

Q12. Which alcohol type is generally resistant to oxidation by mild oxidizing agents?

• Primary alcohols
• Secondary alcohols
• Tertiary alcohols
• Benzylic alcohols

Correct Answer: Tertiary alcohols

Q13. In the iodoform test, what is the chemical identity of the yellow precipitate formed?

• 2,4-Dinitrophenylhydrazone
• Triiodomethane (CHI3)
• Pale green chromium compound
• Silver mirror (Ag)

Correct Answer: Triiodomethane (CHI3)

Q14. Which test would you use to detect a benzylic alcohol selectively due to its ease of oxidation?

• Tollens’ reagent
• KMnO4 oxidation producing carboxylic acid
• Lucas test only
• Ferric chloride test

Correct Answer: KMnO4 oxidation producing carboxylic acid

Q15. What observation indicates a positive chromic acid test for an alcohol?

• Evolution of nitrogen gas
• Color change from orange to green/blue
• Immediate precipitate of silver
• Formation of a purple complex

Correct Answer: Color change from orange to green/blue

Q16. Which alcohol will show immediate turbidity with Lucas reagent: benzyl alcohol, ethanol, cyclohexanol, or tert-butanol?

• Benzyl alcohol
• Ethanol
• Cyclohexanol (secondary)
• tert-Butanol

Correct Answer: tert-Butanol

Q17. Which reagent is commonly used to convert an alcohol into an alkyl bromide for qualitative identification?

• PBr3 (phosphorus tribromide)
• PCC
• Tollens’ reagent
• FeCl3

Correct Answer: PBr3 (phosphorus tribromide)

Q18. A primary aliphatic alcohol when treated with Jones reagent will typically be oxidized to:

• An alkane
• An aldehyde followed further to carboxylic acid
• An ether
• A tertiary alcohol

Correct Answer: An aldehyde followed further to carboxylic acid

Q19. Which alcoholic substrate gives positive iodoform test and is also a methyl ketone?

• Propan-2-ol (isopropanol)
• Butan-2-one (methyl ethyl ketone)
• tert-Butanol
• Benzyl alcohol

Correct Answer: Butan-2-one (methyl ethyl ketone)

Q20. How does benzyl alcohol behave in Lucas test compared to a typical primary alcohol?

• Reacts immediately like tertiary alcohols
• Does not react at all
• Reacts faster than aliphatic primary alcohols due to benzylic stabilization
• Gives a green color with Lucas reagent

Correct Answer: Reacts faster than aliphatic primary alcohols due to benzylic stabilization

Q21. Which test is most appropriate to distinguish an alcohol from an ether?

• Sodium metal test (H2 evolution)
• Tollens’ test
• Lucas test
• Ferric chloride

Correct Answer: Sodium metal test (H2 evolution)

Q22. What is the main mechanistic pathway in the Lucas test for tertiary alcohols?

• SN2 nucleophilic substitution
• Electrophilic addition
• SN1 substitution via carbocation
• Radical chain mechanism

Correct Answer: SN1 substitution via carbocation

Q23. Which reagent combination forms the Jones reagent commonly used in alcohol oxidation?

• Chromium trioxide (CrO3) in dilute sulfuric acid and acetone
• ZnCl2 in HCl
• PCC in dichloromethane
• Tollen’s reagent (AgNO3/NH3)

Correct Answer: Chromium trioxide (CrO3) in dilute sulfuric acid and acetone

Q24. If a secondary alcohol is treated with PCC, the expected product is:

• An aldehyde
• A ketone
• A carboxylic acid
• An alkene

Correct Answer: A ketone

Q25. Which of the following alcohols gives a positive Tollens’ test?

• Ethanal (acetaldehyde, but this is not an alcohol)
• Ethanol
• Isobutanol
• Benzyl alcohol

Correct Answer: Ethanal (acetaldehyde, but this is not an alcohol)

Q26. Which test would you choose to identify a tertiary alcohol by its resistance to oxidation and esterification patterns?

• Chromic acid oxidation showing no color change
• Iodoform test showing yellow precipitate
• Ferric chloride test producing violet color
• Tollens’ reagent producing silver mirror

Correct Answer: Chromic acid oxidation showing no color change

Q27. Reaction of an alcohol with acetic anhydride in the presence of pyridine producing an ester indicates what about the alcohol?

• It lacks an –OH group
• It is capable of undergoing acetylation (presence of –OH)
• It is a tertiary alcohol only
• It is resistant to substitution reactions

Correct Answer: It is capable of undergoing acetylation (presence of –OH)

Q28. Which functional group will give a violet color with ferric chloride but not with Lucas reagent?

• Primary aliphatic alcohol
• Phenol
• Tertiary alcohol
• Ether

Correct Answer: Phenol

Q29. Which alcohol would be oxidized to an aldehyde and stop there when treated with PCC but would be further oxidized to acid by KMnO4?

• Benzyl alcohol
• tert-Butanol
• Isopropyl alcohol
• 1-Propanol

Correct Answer: 1-Propanol

Q30. A tertiary alcohol treated with Lucas reagent shows no visible change. What is the likely reason?

• Tertiary alcohols never react with Lucas reagent
• Lucas reagent is only for aldehydes
• If no change occurs, reagent may be too cold or impure; tertiary normally reacts fast
• Tertiary alcohols immediately give iodine precipitate instead

Correct Answer: If no change occurs, reagent may be too cold or impure; tertiary normally reacts fast

Q31. Which structural feature in an alcohol favors a positive iodoform test?

• Presence of an –OH on a tertiary carbon with no methyl
• A methyl group adjacent to the carbonyl or an –CHO group
• A methyl group attached to the carbon bearing the –OH (CH3CH(OH)–)
• A phenolic –OH

Correct Answer: A methyl group attached to the carbon bearing the –OH (CH3CH(OH)–)

Q32. When performing the Lucas test on a mixture, which statement is correct about reaction times?

• Primary reacts fastest, tertiary slowest
• Secondary reacts immediately, tertiary in hours
• Tertiary reacts immediately, secondary within minutes, primary very slowly or not at room temperature
• All alcohols react at the same rate

Correct Answer: Tertiary reacts immediately, secondary within minutes, primary very slowly or not at room temperature

Q33. Which test will give a positive result for ethanol specifically among small alcohols?

• Only Lucas test
• Iodoform test producing yellow precipitate
• Ferric chloride producing violet complex
• Tollens’ reagent giving silver mirror

Correct Answer: Iodoform test producing yellow precipitate

Q34. Which statement correctly compares benzyl alcohol and tertiary alcohols in oxidation?

• Benzyl alcohol is resistant while tertiary oxidizes easily
• Benzyl alcohol oxidizes readily (even mild oxidants) while tertiary alcohols resist oxidation
• Both oxidize equally under mild conditions
• Neither oxidizes with KMnO4

Correct Answer: Benzyl alcohol oxidizes readily (even mild oxidants) while tertiary alcohols resist oxidation

Q35. Which qualitative test can confirm the formation of an ester from an alcohol?

• Smell/characteristic odor and IR band for ester C=O
• Tollen’s silver mirror
• Lucas reagent turbidity
• Ferric chloride color

Correct Answer: Smell/characteristic odor and IR band for ester C=O

Q36. Which reagent combination will convert a primary alcohol to an alkyl chloride under mild conditions for identification?

• ZnCl2/HCl (Lucas reagent)
• AgNO3/NH3
• PCC in dichloromethane
• Conc. HNO3

Correct Answer: ZnCl2/HCl (Lucas reagent)

Q37. Why does tert-butanol react faster than 1-butanol in the Lucas test?

• tert-Butanol is less soluble in reagent
• Tertiary carbocation formed is more stable facilitating SN1
• Lucas reagent selectively oxidizes tertiary alcohols
• 1-Butanol has no –OH group

Correct Answer: Tertiary carbocation formed is more stable facilitating SN1

Q38. Which alcohol will NOT give a positive iodoform test?

• Ethanol
• Propan-2-ol
• Butan-1-ol
• Ethyl methyl ketone (as ketone)

Correct Answer: Butan-1-ol

Q39. On treatment with conc. H2SO4, a tertiary alcohol readily undergoes which qualitative change useful for identification?

• Oxidation to aldehyde
• Dehydration to give an alkene (olefin)
• Reduction to alkane
• Formation of a carboxylic acid

Correct Answer: Dehydration to give an alkene (olefin)

Q40. Which reagent set would you use to distinguish phenol from an aliphatic alcohol?

• Perform Lucas test only
• Ferric chloride test and sodium bicarbonate test
• Tollen’s reagent and iodoform test
• PBr3 conversion and observation of H2 evolution

Correct Answer: Ferric chloride test and sodium bicarbonate test

Q41. Which statement about oxidation susceptibility is true?

• Benzylic and allylic alcohols oxidize more easily than simple aliphatic alcohols
• Tertiary alcohols oxidize most readily to acids
• Aliphatic primary alcohols are inert to strong oxidants
• All alcohols equally resist oxidation

Correct Answer: Benzylic and allylic alcohols oxidize more easily than simple aliphatic alcohols

Q42. The presence of a free –OH group can be confirmed by which IR absorption region qualitative check?

• A broad peak near 3200–3600 cm−1
• A sharp peak at 1700 cm−1
• A band at 2100 cm−1
• No peaks in the IR spectrum

Correct Answer: A broad peak near 3200–3600 cm−1

Q43. Which test would differentiate ethanol from ethyl ether?

• Sodium metal reaction giving H2 for ethanol but not for ether
• Iodoform test positive for ether only
• Lucas test positive for ether only
• Ferric chloride gives violet for ether

Correct Answer: Sodium metal reaction giving H2 for ethanol but not for ether

Q44. A secondary alcohol reacts with PCC to give which product and what does that indicate for qualitative tests?

• Alcohol remains unchanged — PCC is inert
• Aldehyde — indicates primary alcohol originally
• Ketone — confirms secondary alcohol
• Carboxylic acid — typical for secondary alcohols

Correct Answer: Ketone — confirms secondary alcohol

Q45. What qualitative sign suggests formation of an alkyl chloride after treating alcohol with ZnCl2/HCl?

• Formation of a silver mirror
• Separation of an oily layer or turbidity
• Evolution of CO2 gas
• Immediate purple coloration

Correct Answer: Separation of an oily layer or turbidity

Q46. Which alcohol will show a green color on oxidation with chromic acid?

• Tertiary butanol
• Primary ethanol
• Alkanes with no –OH
• Ethers such as diethyl ether

Correct Answer: Primary ethanol

Q47. Which structural feature would cause an alcohol to give both a positive Lucas test quickly and be oxidizable by mild oxidants?

• Presence of a tertiary carbon only
• Benzylic secondary alcohol
• Long-chain primary alcohol with no adjacent unsaturation
• Simple tertiary alcohol with no benzylic stabilization

Correct Answer: Benzylic secondary alcohol

Q48. A compound gives a yellow crystalline precipitate on treatment with I2/NaOH and a sharp IR band at ~1700 cm−1 after oxidation. What was the starting functional group?

• Primary amine
• Alcohol with a methyl ketone or ethanol type structure
• Ether
• Unsubstituted alkane

Correct Answer: Alcohol with a methyl ketone or ethanol type structure

Q49. Why is PCC preferred over KMnO4 for sensitive qualitative oxidation where aldehyde detection is required?

• PCC oxidizes primary alcohols all the way to acids faster
• PCC selectively oxidizes primary alcohols to aldehydes without further oxidation to acids
• PCC is a basic reagent that protects aldehydes
• PCC gives a colored complex unique to alcohols

Correct Answer: PCC selectively oxidizes primary alcohols to aldehydes without further oxidation to acids

Q50. Which combined set of observations would identify a compound as ethanol in a qualitative lab screen?

• No reaction with sodium, negative iodoform, no ester formation
• Positive sodium metal (H2), positive iodoform (yellow precipitate), oxidizable to acetic acid by strong oxidant
• Immediate Lucas turbidity, ferric chloride violet, resistant to oxidation
• Immediate silver mirror with Tollens’ reagent and no IR OH band

Correct Answer: Positive sodium metal (H2), positive iodoform (yellow precipitate), oxidizable to acetic acid by strong oxidant

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.

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