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Alcohols, Phenols and Ethers Set-6 MCQ Online Practice Test | Class 12 | Quiz Tweek

Alcohols, Phenols and Ethers Set-6

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

This chapter is central because it links structure with key chemical behaviors such as acid-base strength of phenols, selective cleavage/addition reactions of ethers, and common synthetic strategies (Williamson synthesis, acid-catalysed etherification, Reimer–Tiemann, etc.). These concepts are repeatedly tested in CBSE boards and frequently appear in JEE/NEET through reaction-based reasoning, stereochemistry, and mechanism/acid-strength comparisons.

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Q1. On acid-catalysed dehydration of ethanol to form diethyl ether according to the equation $2\,C_2H_5OH \xrightarrow{H^+} C_2H_5\!-\!O\!-\!C_2H_5 + H_2O$ , how many molecules of water are produced when $46\ \mathrm{g}$ of ethanol is completely converted to diethyl ether?

(A)

$1.2044\times10^{24}$ molecules

(B)

$3.011\times10^{23}$ molecules

(C)

$6.022\times10^{23}$ molecules

(D)

$1.506\times10^{23}$ molecules

Q2. A mixture containing $1.0$ mol of phenol ( $C_6H_5OH$ ) and $1.0$ mol of ethanol ( $CH_3CH_2OH$ ) is treated with $1.0$ mol of $NaH$ and then with $1.0$ mol of $CH_3I$ . Which is the major organic product obtained?

(A)

Anisole ( $C_6H_5OCH_3$ ) as the major product with negligible $CH_3OCH_2CH_3$

(B)

Methyl ethyl ether ( $CH_3OCH_2CH_3$ ) as the major product

(C)

A 1:1 mixture of anisole and methyl ethyl ether

(D)

No ether formation; only $H_2$ and unreacted alcohols are obtained

Q3. Treatment of tert‑butyl methyl ether $(CH_3)_3COCH_3$ with excess hydriodic acid ( $HI$ ) gives which major products?

(A)

$CH_3I$ and $(CH_3)_3COH$

(B)

$CH_2\!=\!C(CH_3)_2$ and $CH_3I$

(C)

A mixture of $CH_3I$ and isobutane

(D)

$(CH_3)_3CI$ and $CH_3OH$

Q4. Assertion (A): $p$ ‑Nitrophenol is a stronger acid than $o$ ‑nitrophenol.
Reason (R): In $o$ ‑nitrophenol the $-NO_2$ group forms an intramolecular hydrogen bond with the phenoxide ion, thereby stabilizing the phenoxide ion more than in the para isomer.

(A)

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

(B)

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

(C)

A is true but R is false.

(D)

A is false but R is true.

Q5. On treatment of 2‑methoxypropane $(CH_3)_2CHOCH_3$ with excess hydrobromic acid ( $HBr$ ) under reflux, the major organic products obtained are:

(A)

$CH_3Br$ and $(CH_3)_2CHOH$

(B)

$CH_3Br$ and $(CH_3)_2CHBr$

(C)

$CH_3Br$ and $CH_3CH\!=\!CH_2$

(D)

$(CH_3)_2CHBr$ and $CH_3OH$

Q6. How many structural isomers (ignoring stereoisomers) correspond to the molecular formula $C_4H_{10}O$ that are either alcohols or ethers? (Consider only acyclic isomers.)

(A)

(B)

(C)

(D)

Q7. Which of the following compounds is the most acidic? (Acidity determined by stabilization of the phenoxide ion via resonance/inductive effects.)

(A)

Phenol ( $C_6H_5OH$ )

(B)

p‑Cresol (4‑methylphenol, $C_7H_8O$ )

(C)

m‑Nitrophenol ( $C_6H_4(NO_2)OH$ )

(D)

p‑Nitrophenol ( $C_6H_4(NO_2)OH$ )

Q8. When treated with excess HI at 0°C, which of the following ethers will give tert‑butyl iodide as the major organic halide upon cleavage?

(A)

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

(B)

Diethyl ether ( $CH_3CH_2OCH_2CH_3$ )

(C)

Anisole ( $C_6H_5OCH_3$ )

(D)

Ethyl isopropyl ether ( $CH_3CH_2OCH(CH_3)_2$ )

Q9. Assertion (A): The Reimer–Tiemann reaction of phenol with chloroform ( $CHCl_3$ ) in the presence of base gives predominantly ortho‑hydroxybenzaldehyde (salicylaldehyde).
Reason (R): The dichlorocarbene intermediate ( $:CCl_2$ ) generated from chloroform first attacks the para position of phenoxide and then migrates to the ortho position during workup, which is why the ortho‑aldehyde is obtained.

(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 but R is false.

(D)

Both A and R are false.

Q10. Consider the two alcohols: neopentyl alcohol ( $(CH_3)_3CCH_2OH$ ) and tert‑butanol ( $(CH_3)_3COH$ ). Which statement best describes their relative reactivity toward conversion to alkyl bromides with HBr?

(A)

Neopentyl alcohol reacts faster than tert‑butanol under identical conditions.

(B)

tert‑Butanol reacts much faster; neopentyl alcohol reacts very slowly because steric hindrance and the instability of a neopentyl carbocation prevent both SN1 and SN2 pathways efficiently.

(C)

Both react at similar rates because both have three methyl groups attached to the same carbon skeleton.

(D)

Neither reacts with HBr; both must first be converted to tosylates before substitution can occur.

Q11. Among the following isomeric alcohols (formula $C_4H_{10}O$ ), which has the highest boiling point?

(A)

$CH_3CH(OH)CH_2CH_3$ (2-butanol)

(B)

$(CH_3)_2CHCH_2OH$ (2-methyl-1-propanol, isobutanol)

(C)

$CH_3CH_2CH_2CH_2OH$ (1-butanol)

(D)

$(CH_3)_3COH$ (2-methyl-2-propanol, tert-butanol)

Q12. On treatment with excess HI, ethyl tert‑butyl ether $CH_3CH_2-O-C(CH_3)_3$ is cleaved. The major alkyl iodide formed is:

(A)

$C(CH_3)_3I$ (tert‑butyl iodide)

(B)

$CH_3CH_2I$ (ethyl iodide)

(C)

A 1:1 mixture of $C(CH_3)_3I$ and $CH_3CH_2I$

(D)

No alkyl iodide; only alcohols are obtained

Q13. Which pair of reagents will give the highest yield of 1‑methoxypropane ( $CH_3OCH_2CH_2CH_3$ ) by Williamson ether synthesis with minimal side reactions?

(A)

$CH_3O^-Na^+$ and $CH_3CH(CH_3)Br$ (methyl alkoxide + isopropyl bromide)

(B)

$CH_3CH_2O^-Na^+$ and $CH_3I$ (ethoxide + methyl iodide)

(C)

$CH_3CH_2O^-Na^+$ and $CH_3CH_2CH_2Br$ (ethoxide + n‑propyl bromide)

(D)

$CH_3CH_2CH_2O^-Na^+$ and $CH_3I$ (n‑propoxide + methyl iodide)

Q14. Which of the following methods is most suitable to prepare 2‑methoxybutane ( $CH_3OCH(CH_3)CH_2CH_3$ ) from 2‑butanol and methanol with the highest selectivity and minimum side‑products?

(A)

Mix 2‑butanol and excess methanol and heat with concentrated $H_2SO_4$ (acid‑catalysed etherification)

(B)

Convert 2‑butanol to sodium 2‑butoxide ( $CH_3CH(ONa)CH_2CH_3$ ) and react with $CH_3I$ (Williamson method)

(C)

React sodium methoxide ( $CH_3ONa$ ) with 2‑bromobutane ( $CH_3CH(Br)CH_2CH_3$ ) (Williamson with methyl alkoxide and secondary halide)

(D)

Heat 2‑butanol alone with acid to effect self‑dehydration ( $2R–OH \xrightarrow{H^+} R–O–R + H_2O$ )

Q15. Optically active (R)‑2‑butanol ( $CH_3CH(OH)CH_2CH_3$ ) is reacted separately with (i) concentrated HBr and (ii) $PBr_3$ . Which statement correctly describes the stereochemical outcome for the 2‑bromobutane formed in each case?

(A)

(i) Racemic 2‑bromobutane (due to carbocation, SN1); (ii) (S)‑2‑bromobutane (inversion by $PBr_3$ via SN2)

(B)

(i) (S)‑2‑bromobutane (inversion); (ii) Racemic 2‑bromobutane (racemisation)

(C)

(i) Racemic; (ii) Racemic

(D)

(i) (S)‑2‑bromobutane (inversion); (ii) (S)‑2‑bromobutane (retention)

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