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Alcohols, Phenols and Ethers — NEET & JEE MCQs with answers
Alcohols, phenols and ethers are oxygen-containing organic compounds: an alcohol has one or more –OH groups directly attached to carbon atom(s) of an aliphatic system, a phenol has –OH directly attached to carbon atom(s) of an aromatic ring, and an ether results when the hydrogen of the –OH group of an alcohol or phenol is replaced by an alkyl or aryl group. The chapter covers their classification, nomenclature, preparation, physical properties and reactions, including the greater acidity of phenols compared with alcohols and the cleavage of ethers by hydrogen halides.
Topics in this chapter
- 7.1 Classification of Alcohols, Phenols and Ethers
- 7.2 Nomenclature of Alcohols, Phenols and Ethers
- 7.3 Structures of Functional Groups in Alcohols, Phenols and Ethers
- 7.4 Alcohols and Phenols
- 7.5 Some Commercially Important Alcohols
- 7.6 Ethers
Free practice questions
NCERT prints '2-methylcyclopentanol'. This tells us that the ring carries
- A. a hydroxyl group at C-1 and a methyl group at C-2 of a five-membered ring
- B. a hydroxyl group at C-2 and a methyl group at C-1 of a five-membered ring
- C. two methyl groups on a six-membered ring
- D. a hydroxyl group at C-2 of a six-membered ring
Show answer
Answer: A — Option A is correct. The 'cyclopentan' stem fixes a five-membered ring, the 'ol' ending with C-1 implied fixes the hydroxyl group at C-1, and the locant 2 places the methyl group on the adjacent ring carbon.
NCERT Class 12 Chemistry Part-2 · Ch 7 · §7.2 ("2-Methylcyclopentanol")
Commercial alcohol is made unfit for drinking by mixing in it:
- A. formaldehyde and varnish
- B. carbon dioxide and ethanoic acid
- C. copper sulphate and pyridine
- D. invertase and zymase
Show answer
Answer: C — Option C is correct. NCERT: commercial alcohol is made unfit for drinking by mixing in it some copper sulphate and pyridine.
NCERT Class 12 Chemistry Part-2 · Ch 7 · §7.5 ("by mixing in it some copper sulphate (to give it a colour) and pyridine")
According to NCERT, the properties of alcohols and phenols are chiefly due to
- A. The alkyl or aryl group
- B. The carbon skeleton alone
- C. The hydroxyl group
- D. The number of $\pi$ bonds present
Show answer
Answer: C — Option C is correct. NCERT states that alcohols and phenols consist of two parts, an alkyl/aryl group and a hydroxyl group, and that the properties are chiefly due to the hydroxyl group, the alkyl or aryl group simply modifying them.
NCERT Class 12 Chemistry Part-2 · Ch 7 · §7.4.3 ("Alcohols and phenols consist of two parts, an alkyl/aryl group and a")
Which temperature must be used with sulphuric acid if ethanol is to give the **ether** as the main product?
- A. 573 K
- B. 413 K
- C. 443 K
- D. 337 K
Show answer
Answer: B — Option B is correct. NCERT gives 413 K for the ether (ethoxyethane) and the higher 443 K for the alkene (ethene).
NCERT Class 12 Chemistry Part-2 · Ch 7 · §7.6.1 ("At 413 K, ethoxyethane is the main product.")
Which of the following is a benzylic alcohol?
- A. $\mathrm{C_6H_5\!-\!OH}$
- B. $\mathrm{C_6H_5\!-\!CH_2\!-\!OH}$
- C. $\mathrm{C_6H_5\!-\!OCH_3}$
- D. $\mathrm{CH_2=CH\!-\!CH_2\!-\!OH}$
Show answer
Answer: B — Option B is correct. $\mathrm{C_6H_5\!-\!CH_2\!-\!OH}$ carries its hydroxyl group on an $sp^3$ carbon attached to the ring. $\mathrm{C_6H_5\!-\!OH}$ is a phenol, $\mathrm{C_6H_5\!-\!OCH_3}$ is an ether with no hydroxyl group, and the last is allylic.
NCERT Class 12 Chemistry Part-2 · Ch 7 · §7.1.1 ("Benzylic alcohols: In these alcohols, the -OH group is attached")
Which description of the carbon–oxygen bond in an alcohol matches NCERT's account?
- A. A sigma bond from $sp^2$–$sp^2$ overlap, with the bond angle a little below tetrahedral
- B. A sigma bond from $sp^3$–$sp^3$ overlap, with the bond angle a little below tetrahedral
- C. A bond with partial double bond character, with the angle a little above tetrahedral
- D. A sigma bond from $sp^3$–$sp^3$ overlap, with the angle a little above tetrahedral
Show answer
Answer: B — Option B is correct. Two separate statements have to be combined: the sigma bond arises from $sp^3$–$sp^3$ overlap, and the bond angle in alcohols is slightly *less* than the tetrahedral angle. Partial double bond character is asserted only for phenol, and a widened angle only for ethers.
NCERT Class 12 Chemistry Part-2 · Ch 7 · §7.3 ("in alcohols is slightly less than the tetrahedral")
Methyl isopropyl ether, $\mathrm{(CH_3)_2CHOCH_3}$, is tabulated with which systematic name?
- A. 1-methoxypropane
- B. 2-methoxypropane
- C. 2-methoxybutane
- D. 1-methoxy-2-methylpropane
Show answer
Answer: B — Option B is correct. The larger group is isopropyl, so propane is the parent, and the methoxy group is attached to its middle carbon, C-2, giving 2-methoxypropane. NCERT lists this against the common name methyl isopropyl ether.
NCERT Class 12 Chemistry Part-2 · Ch 7 · §7.2 ("2-Methoxypropane")
In primary, secondary and tertiary alcohols the hydroxyl group is attached respectively to
- A. one, two and three carbon atoms
- B. an $sp$, an $sp^2$ and an $sp^3$ carbon atom
- C. a primary, a secondary and a tertiary carbon atom
- D. an alkyl, an allylic and a benzylic carbon atom
Show answer
Answer: C — Option C is correct. NCERT introduces the three types by saying that in them the hydroxyl group is attached to a primary, a secondary and a tertiary carbon atom respectively. A hydroxyl group is of course attached to only one carbon in every case.
NCERT Class 12 Chemistry Part-2 · Ch 7 · §7.1.1 ("alcohols, the -OH group is attached to primary, secondary and")
In phenols, the reactions that take place on the aromatic ring are
- A. Electrophilic substitution reactions
- B. Nucleophilic substitution reactions
- C. Free-radical addition reactions
- D. Elimination reactions
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Answer: A — Option A is correct. NCERT states that in phenols the reactions on the aromatic ring are electrophilic substitution reactions. Nucleophilic substitution, free-radical addition and elimination are not the ring reactions described.
NCERT Class 12 Chemistry Part-2 · Ch 7 · §7.4.4 ("electrophilic substitution reactions (Unit 9, Class XI). The -OH group")
Which of the following is **not** a condition NCERT lays down for preparing an ether by acid dehydration of an alcohol?
- A. The alkyl group should be unhindered
- B. The temperature should be kept low
- C. Only primary alkyl groups are suitable
- D. The alkyl halide used should be primary
Show answer
Answer: D — Option D is correct as the answer to a NOT question. No alkyl halide is used at all in the dehydration route — that reagent belongs to Williamson synthesis. The other three are stated requirements of the dehydration method.
NCERT Class 12 Chemistry Part-2 · Ch 7 · §7.6.1 ("The method is suitable for the preparation of ethers having")
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