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Alcohols, Phenols and Ethers Set-4 MCQ Online Practice Test | Class 12 | Quiz Tweek

Alcohols, Phenols and Ethers Set-4

Practice Important MCQs for Alcohols, Phenols and Ethers — Chemistry, Class 12.

This chapter is crucial because it links structure with reactivity: you learn how alcohols/phenols/ethers react under acidic and nucleophilic conditions, how substituents and intramolecular hydrogen bonding affect acidity and orientation, and how cleavage/oxidation/dehydration pathways are decided—topics frequently tested in CBSE and in JEE/NEET for direct mechanism and product-formation questions.

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Q1. When $CH_3CH(OH)CH_2CH_3$ is dehydrated using $conc.\ H_2SO_4$ at 443 K, which alkene is formed predominantly?

(A)

$CH_3CH_2CH=CH_2$ (1‑butene)

(B)

$cis\text{-}CH_3CH=CHCH_3$ (cis‑2‑butene)

(C)

$trans\text{-}CH_3CH=CHCH_3$ (trans‑2‑butene)

(D)

A 1:1 mixture of $cis\text{-}CH_3CH=CHCH_3$ and $trans\text{-}CH_3CH=CHCH_3$

Q2. Treatment of $CH_3CH(CH_3)OCH_2CH_3$ (isopropyl ethyl ether) with excess $HI$ at room temperature gives which major alkyl iodide?

(A)

$CH_3CH(CH_3)I$ (isopropyl iodide)

(B)

$CH_3CH_2I$ (ethyl iodide) (only)

(C)

Equal amounts of $CH_3CH_2I$ and $CH_3CH(CH_3)I$

(D)

$CH_3CH_2I$ (ethyl iodide) predominant over $CH_3CH(CH_3)I$ (about $3:1$ )

Q3. Arrange the following in increasing acidity (least → most): $p$ ‑cresol ( $p$ ‑ $CH_3C_6H_4OH$ ), phenol ( $C_6H_5OH$ ), $o$ ‑nitrophenol ( $o$ ‑ $O_2NC_6H_4OH$ ), $p$ ‑nitrophenol ( $p$ ‑ $O_2NC_6H_4OH$ ).

(A)

$p\text{-}CH_3C_6H_4OH < C_6H_5OH < p\text{-}O_2NC_6H_4OH < o\text{-}O_2NC_6H_4OH$

(B)

$C_6H_5OH < p\text{-}CH_3C_6H_4OH < o\text{-}O_2NC_6H_4OH < p\text{-}O_2NC_6H_4OH$

(C)

$p\text{-}CH_3C_6H_4OH < o\text{-}O_2NC_6H_4OH < C_6H_5OH < p\text{-}O_2NC_6H_4OH$

(D)

$p\text{-}CH_3C_6H_4OH < C_6H_5OH < o\text{-}O_2NC_6H_4OH < p\text{-}O_2NC_6H_4OH$

Q4. Arrange the following ethers in order of increasing ease of cleavage by $HI$ (slowest → fastest): anisole ( $C_6H_5OCH_3$ ), diethyl ether ( $CH_3CH_2OCH_2CH_3$ ), methyl tert‑butyl ether ( $(CH_3)_3COCH_3$ ).

(A)

$C_6H_5OCH_3 < CH_3CH_2OCH_2CH_3 < (CH_3)_3COCH_3$

(B)

$(CH_3)_3COCH_3 < CH_3CH_2OCH_2CH_3 < C_6H_5OCH_3$

(C)

$C_6H_5OCH_3 < (CH_3)_3COCH_3 < CH_3CH_2OCH_2CH_3$

(D)

$CH_3CH_2OCH_2CH_3 < C_6H_5OCH_3 < (CH_3)_3COCH_3$

Q5. Starting from phenol ( $C_6H_5OH$ ), which sequence of reagents will give predominantly $p$ ‑nitroanisole ( $p$ ‑ $O_2NC_6H_4OCH_3$ ) in the highest yield?

(A)

(i) Nitration: $HNO_3/H_2SO_4$ → (ii) Methylation: $CH_3I/K_2CO_3$

(B)

(i) Methylation: $CH_3I/K_2CO_3$ → (ii) Nitration: $HNO_3/H_2SO_4$ (controlled temperature)

(C)

(i) Acetylation: $Ac_2O/pyridine$ → (ii) Nitration: $HNO_3/H_2SO_4$ → (iii) Hydrolysis: $H_2O/\Delta$ → (iv) Methylation: $CH_3I/K_2CO_3$

(D)

(i) Sulfonation: $SO_3/H_2SO_4$ → (ii) Nitration: $HNO_3/H_2SO_4$ → (iii) Desulfonation: $H_2O/\Delta$ → (iv) Methylation: $CH_3I/K_2CO_3$

Q6. Among the following alcohols, which one has the highest normal boiling point? Consider only intermolecular forces and molecular structure.

(A)

( $\mathrm{CH_3CH_2CH_2OH}$ ) 1-propanol

(B)

( $\mathrm{CH_3CH(OH)CH_3}$ ) 2-propanol

(C)

( $\mathrm{CH_3CH_2CH_2CH_2OH}$ ) 1-butanol

(D)

( $\mathrm{(CH_3)_3COH}$ ) tert-butanol

Q7. When methyl tert‑butyl ether ( $\mathrm{(CH_3)_3COCH_3}$ ) is treated with excess hydrogen iodide ( $\mathrm{HI}$ ) at room temperature, the major organic product(s) expected are:

(A)

( $\mathrm{CH_3I + (CH_3)_3COH}$ ) methyl iodide + tert‑butanol

(B)

( $\mathrm{(CH_3)_3CI + CH_3OH}$ ) tert‑butyl iodide + methanol

(C)

( $\mathrm{CH_2=C(CH_3)_2 + CH_3I}$ ) isobutylene + methyl iodide

(D)

Equimolar mixture of ( $\mathrm{CH_3I}$ ) and ( $\mathrm{(CH_3)_3CI}$ )

Q8. Which of the following compounds will react fastest with aqueous $\mathrm{HBr}$ (to give the corresponding alkyl bromide) under standard conditions? Base your choice on mechanism and intermediate stability.

(A)

( $\mathrm{C_6H_5OH}$ ) phenol

(B)

( $\mathrm{C_6H_{11}OH}$ ) cyclohexanol

(C)

( $\mathrm{(CH_3)_2CHOH}$ ) isopropyl alcohol

(D)

( $\mathrm{C_6H_5CH_2OH}$ ) benzyl alcohol

Q9. Assertion: $p$ ‑Nitrophenol is more acidic than $o$ ‑nitrophenol.
Reason: Intramolecular hydrogen bonding in $o$ ‑nitrophenol stabilizes the undissociated molecule (neutral form), thereby decreasing its tendency to lose a proton compared to the para isomer.

(A)

Both Assertion and Reason are true, and Reason correctly explains the Assertion.

(B)

Both Assertion and Reason are true, but Reason does not correctly explain the Assertion.

(C)

Assertion is true but Reason is false.

(D)

Assertion is false but Reason is true.

Q10. Which of the following aryl chlorides will undergo nucleophilic aromatic substitution most readily with methoxide ion ( $\mathrm{CH_3O^-}$ ) in methanol at 25°C?

(A)

( $\mathrm{C_6H_5Cl}$ ) chlorobenzene

(B)

( $p$ ‑ $\mathrm{NO_2C_6H_4Cl}$ ) p‑nitrochlorobenzene

(C)

( $\mathrm{ClC_6H_3(NO_2)_2}$ , 1‑chloro‑2,4‑dinitrobenzene)

(D)

( $m$ ‑ $\mathrm{NO_2C_6H_4Cl}$ ) m‑nitrochlorobenzene

Q11. Among the following compounds, which is the most acidic? Consider resonance, inductive and intramolecular hydrogen‑bonding effects.

(A)

$C_6H_5OH$ (phenol)

(B)

$p$ ‑nitrophenol ( $4$ ‑nitrophenol)

(C)

$o$ ‑nitrophenol ( $2$ ‑nitrophenol)

(D)

$CH_3CH_2OH$ (ethanol)

Q12. Treatment of tert‑butyl methyl ether $CH_3–O–C(CH_3)_3$ with excess $HI$ at room temperature gives which major alkyl iodide as the organic product?

(A)

$C(CH_3)_3I$ (tert‑butyl iodide)

(B)

$CH_3I$ (methyl iodide)

(C)

A roughly equimolar mixture of $CH_3I$ and $C(CH_3)_3I$

(D)

Predominantly $CH_3I$ (methyl iodide) with $C(CH_3)_3I$ as a minor product

Q13. An unknown alcohol A (molecular formula $C_5H_{12}O$ ) on treatment with $PBr_3$ gives only one alkyl bromide: 2‑bromopentane. Oxidation of A with $PCC$ yields exclusively 2‑pentanone. Which isomer is A?

(A)

$CH_3CH_2CH_2CH_2CH_2OH$ (1‑pentanol)

(B)

$CH_3CH_2CH(OH)CH_2CH_3$ (3‑pentanol)

(C)

$(CH_3)_2CHCH_2CH_2OH$ (2‑methyl‑1‑butanol)

(D)

$CH_3CH(OH)CH_2CH_2CH_3$ (2‑pentanol)

Q14. Statement A: The Kolbe–Schmitt carboxylation of sodium phenoxide ( $C_6H_5O^-Na^+$ ) with $CO_2$ under elevated pressure and temperature followed by acidification gives predominantly salicylic acid (o‑hydroxybenzoic acid).
Statement R: The ortho‑selectivity is a consequence of coordination between $Na^+$ and the phenoxide oxygen which positions $CO_2$ to attack the ortho carbon, stabilizing the ortho transition state.

(A)

A is true, R is false.

(B)

A is false, R is true.

(C)

Both A and R are true and R correctly explains A.

(D)

Both A and R are true but R does not explain A.

Q15. Which of the following three‑step sequences converts phenol ( $C_6H_5OH$ ) into $p$ ‑nitrophenol with the highest para‑selectivity (i.e., minimizes ortho substitution)?

(A)

(i) Acetylation: $C_6H_5OH \xrightarrow{CH_3COCl,\,pyridine} C_6H_5OCOCH_3$ ; (ii) Nitration: $HNO_3/H_2SO_4$ ; (iii) Hydrolysis: $H_3O^+$ → $p$ ‑nitrophenol

(B)

(i) Direct nitration: $C_6H_5OH \xrightarrow{HNO_3/H_2SO_4}$ ; (ii) Separate para/isolate; (iii) Purify isolated $p$ ‑isomer

(C)

(i) Methylation: $C_6H_5OH \xrightarrow{CH_3I,\,Ag_2O} C_6H_5OCH_3$ (anisole); (ii) Nitration: $HNO_3/H_2SO_4$ ; (iii) Demethylation: $BBr_3$ → $p$ ‑nitrophenol

(D)

(i) Convert to phenoxide: $C_6H_5OH \xrightarrow{NaOH} C_6H_5O^-Na^+$ ; (ii) Nitration: $HNO_3/H_2SO_4$ ; (iii) Acidify → $p$ ‑/o‑mixture then isolate

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