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Alcohols, Phenols and Ethers Set-5 MCQ Online Practice Test | Class 12 | Quiz Tweek

Alcohols, Phenols and Ethers Set-5

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

This chapter is crucial for CBSE and competitive exams because it links structure with key reactions: preparation and reactions of alcohols and ethers, phenols’ acidity and electrophilic substitution, and stereochemical outcomes in conversions (often tested as assertion/reason and MCQs). Understanding hydrogen bonding, inductive/resonance effects, and SN1/SN2/E2 preferences makes these questions quick and high-scoring.

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Q1. Which of the following compounds has the highest boiling point?

(A)

$CH_3OCH_3$ (dimethyl ether)

(B)

$CH_3NH_2$ (methylamine)

(C)

$CH_3CH_2OH$ (ethanol)

(D)

$CH_3CHO$ (acetaldehyde)

Q2. Which ether among the following is cleaved most readily by $HI$ under mild conditions (i.e., requires the gentlest conditions for C–O bond cleavage)?

(A)

$(CH_3)_3COCH_3$ (methyl tert‑butyl ether)

(B)

$CH_3CH_2OCH_2CH_3$ (diethyl ether)

(C)

$C_6H_5OCH_3$ (anisole)

(D)

$CH_3OCH_3$ (dimethyl ether)

Q3. Arrange the following phenols in order of increasing acidity (least acidic → most acidic): phenol, $m$ ‑nitrophenol, $o$ ‑nitrophenol, $p$ ‑nitrophenol.

(A)

phenol < $o$ ‑nitrophenol < $m$ ‑nitrophenol < $p$ ‑nitrophenol

(B)

phenol < $p$ ‑nitrophenol < $o$ ‑nitrophenol < $m$ ‑nitrophenol

(C)

$m$ ‑nitrophenol < phenol < $o$ ‑nitrophenol < $p$ ‑nitrophenol

(D)

phenol < $m$ ‑nitrophenol < $o$ ‑nitrophenol < $p$ ‑nitrophenol

Q4. In an attempted Williamson ether synthesis, which of the following alkyl halide + alkoxide combinations will predominantly give an alkene (E2 elimination) rather than the desired ether (because SN2 is disfavoured)?

(A)

$CH_3Br + NaOCH_2CH_3$

(B)

$(CH_3)_3CBr + NaOCH_3$

(C)

$C_6H_5CH_2Br + NaOCH_3$

(D)

$CH_3CH_2Br + NaOCH_3$

Q5. Which reagent is most suitable to remove the methyl group from anisole ( $C_6H_5OCH_3$ ) and convert it to phenol under mild conditions without nitration or oxidative cleavage of the aromatic ring?

(A)

hot concentrated $HBr$ (reflux)

(B)

catalytic hydrogenation ( $H_2/Pd$ )

(C)

$BBr_3$ (boron tribromide)

(D)

$KMnO_4$ (oxidative conditions)

Q6. Among the following compounds, which has the lowest boiling point?

(A)

Phenol ( $\mathrm{C_6H_5OH}$ )

(B)

$m$ -Nitrophenol ( $m$ - $\mathrm{NO_2C_6H_4OH}$ )

(C)

$o$ -Nitrophenol ( $o$ - $\mathrm{NO_2C_6H_4OH}$ )

(D)

$p$ -Nitrophenol ( $p$ - $\mathrm{NO_2C_6H_4OH}$ )

Q7. Arrange the following compounds in order of increasing acidity (least → most acidic):
(i) $m$ -Nitrophenol ( $m$ - $\mathrm{NO_2C_6H_4OH}$ ), (ii) $o$ -Nitrophenol ( $o$ - $\mathrm{NO_2C_6H_4OH}$ ), (iii) $p$ -Nitrophenol ( $p$ - $\mathrm{NO_2C_6H_4OH}$ ), (iv) 2,4-dinitrophenol ( $2,4$ - $\mathrm{(NO_2)_2C_6H_3OH}$ ).

(A)

(ii) $<$ (i) $<$ (iii) $<$ (iv)

(B)

(i) $<$ (ii) $<$ (iii) $<$ (iv)

(C)

(i) $<$ (iii) $<$ (ii) $<$ (iv)

(D)

(iv) $<$ (iii) $<$ (ii) $<$ (i)

Q8. Which of the following alcohols will react fastest with $\mathrm{PBr_3}$ to give the corresponding alkyl bromide under typical conditions?

(A)

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

(B)

2-Butanol ( $\mathrm{CH_3CH(OH)CH_2CH_3}$ )

(C)

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

(D)

Benzyl alcohol ( $\mathrm{C_6H_5CH_2OH}$ )

Q9. Assertion (A): $p$ -Nitrophenol is a stronger acid than $o$ -nitrophenol in aqueous solution.
Reason (R): In $o$ -nitrophenol an intramolecular hydrogen bond forms between the $-$ OH and $-$ NO $_2$ group, which reduces the extent of ionization of the hydroxyl proton compared to the para isomer.

(A)

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

(B)

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

(C)

A is true, R is false.

(D)

A is false, R is true.

Q10. Which reagent will convert $(R)$ -2-butanol to $(S)$ -2-bromobutane with inversion of configuration as the major stereochemical outcome while minimizing elimination and rearrangement?

(A)

Conc. $\mathrm{HBr}$ , heat

(B)

$\mathrm{PBr_3}$

(C)

$\mathrm{Br_2}$ , hv

(D)

$\mathrm{SOCl_2}$ (pyridine), then $\mathrm{NaBr}$ , heat

Q11. Among the following compounds, which has the highest boiling point? (Consider hydrogen bonding and molecular branching.)

(A)

$CH_3CH(OH)CH_2CH_3$ (2‑butanol)

(B)

$CH_3CH_2CH_2CH_2OH$ (1‑butanol)

(C)

$(CH_3)_3COH$ (tert‑butanol)

(D)

$CH_3CH_2CH_2CHO$ (butanal)

Q12. Which of the following correctly describes the relative acidity and reactivity in Williamson ether synthesis with $CH_3I$ for $p$ ‑nitrophenol and $m$ ‑nitrophenol?

(A)

$p$ ‑Nitrophenol is more acidic than $m$ ‑nitrophenol, and its phenoxide reacts faster in Williamson synthesis with $CH_3I$ .

(B)

$m$ ‑Nitrophenol is more acidic than $p$ ‑nitrophenol, and its phenoxide reacts faster in Williamson synthesis.

(C)

$m$ ‑Nitrophenol is more acidic, but $p$ ‑nitrophenoxide reacts faster in Williamson synthesis with $CH_3I$ .

(D)

$p$ ‑Nitrophenol is more acidic than $m$ ‑nitrophenol, but the phenoxide from $m$ ‑nitrophenol is more nucleophilic and reacts faster in Williamson synthesis with $CH_3I$ .

Q13. On treatment with excess $HBr$ , methyl tert‑butyl ether ( $CH_3O\!-\!C(CH_3)_3$ ) undergoes cleavage. The major alkyl halide formed is:

(A)

$(CH_3)_3CBr$ (tert‑butyl bromide)

(B)

$CH_3Br$ (methyl bromide)

(C)

A 1:1 mixture of $(CH_3)_3CBr$ and $CH_3Br$

(D)

No reaction under these conditions

Q14. Consider the statements:
S: $p$ ‑Nitrophenol is more acidic than $o$ ‑nitrophenol in aqueous solution.
R: Intramolecular hydrogen bonding in $o$ ‑nitrophenol stabilizes its conjugate base ( $o$ ‑nitrophenoxide), thereby making it less acidic.
Which of the following is correct?

(A)

Both S and R are true and R is the correct explanation of S.

(B)

Both S and R are true but R is not the correct explanation of S.

(C)

S is true but R is false.

(D)

S is false and R is true.

Q15. p‑Cresol ( $p$ ‑methylphenol) is subjected to two different bromination conditions: (i) $N$ ‑bromosuccinimide (NBS) with light ( $h\nu$ ), and (ii) $Br_2$ with $FeBr_3$ . The major organic products X and Y from (i) and (ii) respectively are:

(A)

X = $4$ ‑hydroxybenzyl bromide ( $HO\!-\!C_6H_4\!-\!CH_2Br$ ), Y = 2‑bromo‑4‑methylphenol

(B)

X = 2‑bromo‑4‑methylphenol, Y = $4$ ‑hydroxybenzyl bromide

(C)

X = $4$ ‑bromophenol (ring‑brominated at para), Y = benzyl bromide

(D)

Both (i) and (ii) give a significant mixture of ring‑brominated and benzylic‑brominated products

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