Alcohols, Phenols & Ethers

31 NEET-UG practice questions on Alcohols, Phenols & Ethers, part of Chemistry. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Hard

   Read these statements on the acid-catalysed dehydration of alcohols. A. Ease of dehydration follows the order tertiary > secondary > primary. B. Ethanol with conc. H₂SO₄ at 443 K gives ethene as the main product. C. The slowest step is the protonation of the alcohol. D. Excess ethanol with conc. H₂SO₄ at 413 K gives ethoxyethane. Which of these are correct?

   1. AA, C and D only
   2. BB, C and D only
   3. CA and B only
   4. DA, B and D only

   Show answerHide answer

   Answer: D · A, B and D only

   Dehydration passes through a carbocation, so its ease follows carbocation stability, which makes A correct. Temperature decides the product of ethanol: ethene at 443 K (B), and the ether at 413 K with excess alcohol (D). C is wrong, because protonation is fast and loss of water to form the carbocation is the slowest step.

   • A: This includes C and leaves out B, which is the standard preparation of ethene.
   • B: This includes C and leaves out A, which is the standard reactivity order.
   • C: This leaves out D, though the ether does form at 413 K.

   Remember this

   In acid dehydration, carbocation formation is the slow step; lower temperature with excess alcohol favours the ether.

2. Question 2 · Easy

   Ethane-1,2-diol (0.2 mol) reacts completely with excess sodium. What volume of H₂ forms at STP? (Molar volume = 22.4 L)

   1. A6.72 L
   2. B2.24 L
   3. C8.96 L
   4. D4.48 L

   Show answerHide answer

   Answer: D · 4.48 L

   Each -OH gives half a mole of H₂, so a diol gives 1 mol of H₂ per mole. So 0.2 mol of diol gives 0.2 mol of H₂, and 0.2 × 22.4 = 4.48 L.

   • A: This treats the compound as a triol, taking 0.3 mol of H₂.
   • B: This counts only one -OH group per molecule.
   • C: This forgets that hydrogen is diatomic, taking 0.4 mol of H₂.

   Remember this

   Moles of H₂ with sodium equal half the moles of -OH groups present.

3. Question 3 · Medium

   tert-Butyl ethyl ether is to be made by Williamson synthesis. Which pair of reactants gives it in good yield?

   1. ACH₃CH₂ONa and CH₃CH₂Br
   2. B(CH₃)₃CBr and CH₃CH₂ONa
   3. C(CH₃)₃CONa and CH₃CH₂Br
   4. D(CH₃)₃CONa and (CH₃)₃CBr

   Show answerHide answer

   Answer: C · (CH₃)₃CONa and CH₃CH₂Br

   Williamson synthesis is SN2, so it needs an unhindered, primary alkyl halide. The bulky group must come in as the alkoxide, with CH₃CH₂Br as the substrate.

   • A: This pair gives diethyl ether, not the required ether.
   • B: A tertiary halide with a strong base eliminates to give 2-methylpropene.
   • D: This pair has a tertiary halide, which eliminates, and has no ethyl group at all.

   Remember this

   Keep the alkyl halide primary; a tertiary halide with an alkoxide undergoes elimination and gives the alkene.

4. Question 4 · Easy

   With Lucas reagent at room temperature, which alcohol turns cloudy immediately?

   1. A2-Methylpropan-1-ol
   2. B2-Methylpropan-2-ol
   3. CButan-1-ol
   4. DButan-2-ol

   Show answerHide answer

   Answer: B · 2-Methylpropan-2-ol

   Lucas reagent is conc. HCl with ZnCl₂. Tertiary alcohols form the insoluble alkyl chloride at once by way of a stable carbocation. Secondary alcohols take some minutes and primary ones show no turbidity at room temperature.

   • A: This is a branched primary alcohol, and branching does not change its class.
   • C: This is a primary alcohol, which shows no turbidity at room temperature.
   • D: This is a secondary alcohol, which needs several minutes.

   Remember this

   Lucas turbidity: tertiary at once, secondary in minutes, primary not at room temperature.

5. Question 5 · Medium

   Arrange these compounds in increasing order of acid strength. A. Ethanol B. Phenol C. 4-Methylphenol D. 4-Nitrophenol

   1. AA, B, C, D
   2. BA, C, B, D
   3. CD, B, C, A
   4. DC, A, B, D

   Show answerHide answer

   Answer: B · A, C, B, D

   Phenoxide ions are stabilised by resonance, so phenols are more acidic than ethanol. An electron-donating methyl lowers the acidity of phenol slightly, while an electron-withdrawing nitro at the para position raises it strongly.

   • A: This ranks 4-methylphenol above phenol, treating methyl as electron-withdrawing.
   • C: This reverses the whole order.
   • D: This puts 4-methylphenol below ethanol, ignoring phenoxide resonance.

   Remember this

   Electron-withdrawing groups strengthen a phenol as an acid; electron-donating groups weaken it; every phenol here beats ethanol.

6. Question 6 · Medium

   A sample of 9.4 g of phenol reacts completely with excess bromine water. What mass of the precipitate forms? (C = 12, H = 1, O = 16, Br = 80)

   1. A17.3 g
   2. B9.4 g
   3. C25.2 g
   4. D33.1 g

   Answer and explanation in LearnFree account

7. Question 7 · Hard

   Given below are two statements: Statement I: Anisole with HI gives phenol and methyl iodide, not iodobenzene and methanol. Statement II: tert-Butyl methyl ether with HI gives tert-butyl alcohol and methyl iodide. Choose the correct answer.

   1. AStatement I is incorrect but Statement II is correct
   2. BStatement I is correct but Statement II is incorrect
   3. CBoth Statement I and Statement II are incorrect
   4. DBoth Statement I and Statement II are correct

   Answer and explanation in LearnFree account

8. Question 8 · Easy

   Phenol is shaken with bromine water. What is the white precipitate?

   1. A4-Bromophenol
   2. B2,4,6-Tribromophenol
   3. C2,4-Dibromophenol
   4. D3,5-Dibromophenol

   Answer and explanation in LearnFree account

9. Question 9 · Medium

   Arrange the compounds drawn in order of increasing acid strength. A. Structure A B. Structure B C. Structure C D. Structure D

   

   −+Fit to screenClose

   

   1. AB, A, D, C
   2. BB, A, C, D
   3. CA, B, D, C
   4. DB, D, A, C

   Answer and explanation in LearnFree account

10. Question 10 · Medium

    X and Y in the figure are isomeric alcohols. Given below are two statements: Statement I: With Lucas reagent at room temperature, X turns turbid almost at once, while Y does not. Statement II: On heating with concentrated acid, X dehydrates under milder conditions than Y. Choose the correct answer.

    

    −+Fit to screenClose

    

    1. AStatement I is correct but Statement II is incorrect
    2. BBoth Statement I and Statement II are correct
    3. CStatement I is incorrect but Statement II is correct
    4. DBoth Statement I and Statement II are incorrect

    Answer and explanation in LearnFree account

11. Question 11 · Medium

    Given below are two statements: Statement I: Ethanol is a stronger acid than water. Statement II: Hydroboration-oxidation of propene gives propan-2-ol. Choose the correct answer.

    1. ABoth Statement I and Statement II are incorrect
    2. BStatement I is correct but Statement II is incorrect
    3. CStatement I is incorrect but Statement II is correct
    4. DBoth Statement I and Statement II are correct

    Answer and explanation in LearnFree account

12. Question 12 · Easy

    Phenol is heated with chloroform and aqueous sodium hydroxide, and the mixture is then acidified. The main product is

    1. A2-chlorophenol
    2. Bbenzaldehyde
    3. C2-hydroxybenzoic acid
    4. D2-hydroxybenzaldehyde

    Answer and explanation in LearnFree account

13. Question 13 · Hard

    An alcohol X has the formula C₄H₁₀O. With Lucas reagent at room temperature it turns turbid only after about five minutes, and X is optically active. Identify X.

    1. AButan-1-ol
    2. BButan-2-ol
    3. C2-Methylpropan-1-ol
    4. D2-Methylpropan-2-ol

    Answer and explanation in LearnFree account

14. Question 14 · Medium

    Identify R in the sequence below. Phenol + NaOH → P P + CO₂ (400 K, 4-7 atm), then H⁺ → Q Q + (CH₃CO)₂O, H⁺ → R

    1. A2-Hydroxybenzoic acid
    2. BPhenyl ethanoate
    3. C2-Acetoxybenzoic acid
    4. D4-Acetoxybenzoic acid

    Answer and explanation in LearnFree account

15. Question 15 · Medium

    Methoxybenzene (anisole) is heated with hydrogen iodide. Which products form?

    1. AIodobenzene and iodomethane
    2. BPhenol and iodomethane
    3. CIodobenzene and methanol
    4. DBenzene and methanol

    Answer and explanation in LearnFree account

16. Question 16 · Medium

    Match List-I with List-II. List-I (reaction) A. Ethanol with pyridinium chlorochromate B. Propan-2-ol vapour over Cu at 573 K C. 2-Methylpropan-2-ol vapour over Cu at 573 K D. Phenol heated with zinc dust List-II (main organic product) I. Ethanal II. 2-Methylpropene III. Benzene IV. Propanone Choose the correct answer.

    1. AA-I, B-IV, C-III, D-II
    2. BA-I, B-II, C-IV, D-III
    3. CA-IV, B-I, C-II, D-III
    4. DA-I, B-IV, C-II, D-III

    Answer and explanation in LearnFree account

17. Question 17 · Easy

    Arrange the compounds in increasing order of boiling point. A. Ethanol B. Propane C. Propan-1-ol D. Methoxymethane

    1. AD, B, A, C
    2. BB, A, D, C
    3. CB, D, A, C
    4. DC, A, D, B

    Answer and explanation in LearnFree account

18. Question 18 · Medium

    Methyl tert-butyl ether, (CH₃)₃C–O–CH₃, is heated with one equivalent of HI. Which products are formed?

    1. AIodomethane and 2-methylpropan-2-ol
    2. B2-Iodo-2-methylpropane and iodomethane
    3. C2-Methylpropene and iodomethane
    4. D2-Iodo-2-methylpropane and methanol

    Answer and explanation in LearnFree account

19. Question 19 · Hard

    A compound C₇H₈O dissolves in aqueous NaOH and gives a violet colour with neutral FeCl₃. With bromine water it gives a white precipitate of formula C₇H₅OBr₃. Identify the compound.

    1. A4-Methylphenol
    2. BPhenylmethanol
    3. C2-Methylphenol
    4. D3-Methylphenol

    Answer and explanation in LearnFree account

20. Question 20 · Medium

    Considering only structural isomers, how many alcohols and how many ethers have the molecular formula C₄H₁₀O?

    1. A5 alcohols and 3 ethers
    2. B3 alcohols and 3 ethers
    3. C4 alcohols and 3 ethers
    4. D4 alcohols and 2 ethers

    Answer and explanation in LearnFree account

21. Question 21 · Medium

    Butan-1-ol is treated with pyridinium chlorochromate (PCC) in CH₂Cl₂. What is the product?

    1. AButanal
    2. BButanoic acid
    3. CBut-1-ene
    4. DButan-2-one

    Answer and explanation in LearnFree account

22. Question 22 · Medium

    Ethanol is heated with concentrated H₂SO₄ at 413 K. If 92 g of ethanol is converted completely to ethoxyethane, what mass of ether is obtained? (C = 12, H = 1, O = 16)

    1. A37 g
    2. B74 g
    3. C92 g
    4. D148 g

    Answer and explanation in LearnFree account

23. Question 23 · Easy

    In alcoholic fermentation, glucose is converted by the enzyme zymase: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. What mass of ethanol can 180 g of glucose give at most? (C = 12, H = 1, O = 16)

    1. A180 g
    2. B92 g
    3. C46 g
    4. D88 g

    Answer and explanation in LearnFree account

24. Question 24 · Hard

    Phenols and alcohols differ widely in their pKa values. Arrange the following, weakest acid first. A. 4-Nitrophenol B. 4-Methylphenol C. Ethanol D. 3-Nitrophenol

    1. AC, B, A, D
    2. BB, C, D, A
    3. CC, B, D, A
    4. DC, D, B, A

    Answer and explanation in LearnFree account

25. Question 25 · Easy

    Ethanal reacts with methylmagnesium bromide, and the adduct is hydrolysed with dilute acid. The alcohol formed is

    1. Aethanol
    2. Bpropan-1-ol
    3. C2-methylpropan-2-ol
    4. Dpropan-2-ol

    Answer and explanation in LearnFree account