This set of Alcohols MCQs With Answer is crafted for B. Pharm students to reinforce core concepts in alcohol chemistry, including nomenclature, classification (primary, secondary, tertiary), physical properties, hydrogen bonding, acidity/basicity, synthesis and common reactions like oxidation, reduction, substitution and dehydration. Emphasis is placed on mechanism reasoning, reagent selection (PCC, KMnO4, LiAlH4, NaBH4), analytical tests, metabolism (alcohol dehydrogenase), formulation and stability considerations relevant to pharmaceuticals. Practicing these questions develops problem-solving skills for organic synthesis, drug design implications and quality control. Answers provided aid self-assessment. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which of the following correctly describes a primary alcohol?
- An alcohol where the hydroxyl-bearing carbon is attached to three other carbons
- An alcohol where the hydroxyl-bearing carbon is attached to two other carbons
- An alcohol where the hydroxyl-bearing carbon is attached to one other carbon
- An alcohol directly bonded to an aromatic ring
Correct Answer: An alcohol where the hydroxyl-bearing carbon is attached to one other carbon
Q2. Which reagent selectively oxidizes primary alcohols to aldehydes without further oxidation to carboxylic acids?
- Potassium permanganate (KMnO4)
- Chromic acid (H2CrO4)
- Pyridinium chlorochromate (PCC)
- Aqueous nitric acid
Correct Answer: Pyridinium chlorochromate (PCC)
Q3. Which test is classically positive for tertiary alcohols under Lucas test conditions?
- Immediate cloudiness at room temperature
- Cloudiness after several minutes due to carbocation formation
- No reaction (remains clear)
- Formation of yellow precipitate
Correct Answer: Immediate cloudiness at room temperature
Q4. Williamson ether synthesis requires which type of alcohol-derived intermediate?
- Alcohol converted to alkyl chloride
- Deprotonated alkoxide ion
- Carbocation from tertiary alcohol
- Aldehyde intermediate
Correct Answer: Deprotonated alkoxide ion
Q5. Which of the following alcohols will give a positive iodoform test?
- Isopropyl alcohol (propan-2-ol)
- n-Butanol (butan-1-ol)
- Benzyl alcohol
- Tert-butanol
Correct Answer: Isopropyl alcohol (propan-2-ol)
Q6. In pharmaceutical formulations, addition of an alcohol functional group typically affects drug molecules by:
- Decreasing polarity and water solubility
- Increasing volatility markedly
- Increasing hydrogen bonding and often water solubility
- Making molecules permanently ionized at physiological pH
Correct Answer: Increasing hydrogen bonding and often water solubility
Q7. Which reagent is commonly used to reduce aldehydes and ketones to alcohols in organic synthesis?
- PCC
- LiAlH4
- Chromic acid
- Potassium dichromate
Correct Answer: LiAlH4
Q8. Which alcohol oxidation product arises from oxidizing a secondary alcohol?
- Aldehyde
- Ketone
- Carboxylic acid directly
- Alcohol cannot be oxidized
Correct Answer: Ketone
Q9. Phenol differs from aliphatic alcohols primarily because:
- It is more basic than aliphatic alcohols
- Its hydroxyl proton is more acidic due to resonance stabilization of the phenoxide ion
- It cannot form hydrogen bonds
- It undergoes SN2 reactions easily at the OH carbon
Correct Answer: Its hydroxyl proton is more acidic due to resonance stabilization of the phenoxide ion
Q10. During dehydration of alcohols to alkenes, which condition favors E1 mechanism with rearrangements?
- Primary alcohol with strong base
- Tertiary alcohol under acidic conditions
- Primary alcohol under neutral conditions
- Alcohol in presence of hydrogenation catalyst
Correct Answer: Tertiary alcohol under acidic conditions
Q11. Which protecting group is commonly used to protect alcohols during multi-step synthesis?
- Tosyl (Ts) group
- Methyl ester
- Acetal of aldehyde
- Nitro group
Correct Answer: Tosyl (Ts) group
Q12. Which alcohol shows the highest boiling point among the following (assuming similar molecular weight)?
- Tertiary alcohol
- Secondary alcohol
- Primary alcohol
- Alkane of similar weight
Correct Answer: Primary alcohol
Q13. Ethanol metabolism in the liver primarily involves which enzyme?
- Cytochrome P450 reductase
- Alcohol dehydrogenase (ADH)
- Monoamine oxidase
- Acetyl-CoA carboxylase
Correct Answer: Alcohol dehydrogenase (ADH)
Q14. Which statement about hydrogen bonding in alcohols is correct?
- Alcohols cannot form hydrogen bonds with water
- Intramolecular hydrogen bonding always increases boiling point
- Intermolecular hydrogen bonding increases boiling point and solubility in water
- Hydrogen bonding makes alcohols nonpolar
Correct Answer: Intermolecular hydrogen bonding increases boiling point and solubility in water
Q15. Tosylation of an alcohol converts it into a tosylate which is:
- A better leaving group suitable for nucleophilic substitution
- More nucleophilic than the original alcohol
- Irreversibly oxidized form
- Used to convert alcohol into an aldehyde
Correct Answer: A better leaving group suitable for nucleophilic substitution
Q16. Which mechanism best describes SN2 substitution on a primary alkyl alcohol derivative (converted to a good leaving group)?
- Two-step with carbocation intermediate
- One-step backside attack leading to inversion of configuration
- Radical chain mechanism
- Concerted pericyclic rearrangement
Correct Answer: One-step backside attack leading to inversion of configuration
Q17. Which oxidizing agent will oxidize primary alcohols all the way to carboxylic acids under aqueous conditions?
- PCC in dichloromethane
- Swern oxidation
- Potassium permanganate (KMnO4) aqueous
- Hydrogenation with Pd/C
Correct Answer: Potassium permanganate (KMnO4) aqueous
Q18. Which of the following alcohols is chiral?
- 2-Butanol (CH3-CH(OH)-CH2-CH3)
- Methanol
- Ethanol
- 2-Methylpropan-1-ol (isobutanol)
Correct Answer: 2-Butanol (CH3-CH(OH)-CH2-CH3)
Q19. In drug stability, oxidation of benzylic alcohol to carbonyl can be promoted by:
- Exposure to light and oxygen
- Storage under inert atmosphere
- Addition of radical scavengers
- Freezing at -20°C
Correct Answer: Exposure to light and oxygen
Q20. The conversion of an alcohol to an alkyl halide using HBr follows which general mechanism for tertiary alcohols?
- SN2 via backside attack
- E2 elimination only
- SN1 with carbocation intermediate
- Radical halogenation
Correct Answer: SN1 with carbocation intermediate
Q21. Which reagent is commonly used to convert alcohols into alkyl chlorides under mild conditions using an SN2 pathway?
- SOCl2 (thionyl chloride) with pyridine
- Chromic acid
- KMnO4
- PCC
Correct Answer: SOCl2 (thionyl chloride) with pyridine
Q22. The acidity (pKa) of an alcohol is generally around which value in water?
- ~5
- ~10-16
- ~35
- ~0
Correct Answer: ~10-16
Q23. Which statement about dehydration of primary alcohols to give alkenes is true under acidic conditions?
- They readily form stable carbocations and undergo E1 easily
- They typically undergo E2 elimination requiring strong acid and heat
- They are inert and do not dehydrate
- They preferentially form ethers only
Correct Answer: They typically undergo E2 elimination requiring strong acid and heat
Q24. Which of the following is a pharmaceutical implication of alcohol functional groups in drugs?
- They always prevent metabolism
- They can be sites for phase I metabolism (oxidation) and conjugation in phase II
- They universally make drugs lipophilic
- They render drugs completely non-toxic
Correct Answer: They can be sites for phase I metabolism (oxidation) and conjugation in phase II
Q25. Which laboratory drying agent would be appropriate to remove traces of water from an alcohol solution without reacting with the alcohol?
- Benzoyl chloride
- Magnesium sulfate (MgSO4)
- Sodium metal
- Pyridinium chlorochromate
Correct Answer: Magnesium sulfate (MgSO4)
Q26. Which reaction converts an alcohol into an alkene using acid catalysts?
- Hydrogenation
- Dehydration
- Hydroboration
- Nucleophilic substitution
Correct Answer: Dehydration
Q27. Which alcohol-containing drug functional group can form intramolecular hydrogen bonds that influence conformation and bioavailability?
- Alcohol adjacent to carbonyl (β-hydroxy ketone)
- Alkyl chloride
- Quaternary ammonium
- Nitro group
Correct Answer: Alcohol adjacent to carbonyl (β-hydroxy ketone)
Q28. In the context of organic synthesis, Swern oxidation converts primary alcohols to:
- Carboxylic acids directly
- Aldehydes under controlled conditions
- Ketones only
- Alkanes
Correct Answer: Aldehydes under controlled conditions
Q29. Which statement about tert-butanol (t-BuOH) is correct?
- It is a primary alcohol
- It forms stable carbocations and is prone to unimolecular substitutions
- It cannot engage in hydrogen bonding
- It is linear in structure
Correct Answer: It forms stable carbocations and is prone to unimolecular substitutions
Q30. Conversion of an alcohol to a sulfonate ester (e.g., mesylate) primarily serves to:
- Increase basicity of the molecule
- Protect the alcohol irreversibly
- Create a good leaving group to facilitate substitution or elimination
- Oxidize the alcohol to carbonyl
Correct Answer: Create a good leaving group to facilitate substitution or elimination
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