CBSE Class 12 Chemistry Chapter 7 Alcohols, Phenols and Ethers — 20 MCQs with Answers

IUPAC nomenclature is the foundation of organic chemistry scoring. Alcohols are named by replacing the terminal '-e' of the parent alkane with '-ol' and numbering the carbon chain to give the hydroxyl group the lowest locant. Phenols have the hydroxyl group directly attached to a benzene ring; common names like catechol (1,2-benzenediol), resorcinol (1,3-benzenediol) and hydroquinone (1,4-benzenediol) are frequently tested. Ethers use the alkoxy alkane system for IUPAC names or the older 'alkyl alkyl ether' common name. Classification divides alcohols into primary (1°), secondary (2°) and tertiary (3°) based on the carbon bearing the -OH group, while phenols form a separate class. Ethers are classified as simple (identical alkyl groups) or mixed (different alkyl groups). These distinctions directly affect reactivity patterns tested in MCQs. Mastering IUPAC rules from NCERT Exercise 7.1 is non-negotiable.

Alcohols are industrially prepared by hydration of alkenes (Markovnikov addition) and biologically by fermentation of sugars. Laboratory methods include reduction of carbonyl compounds (aldehydes yield 1° alcohols, ketones yield 2° alcohols using LiAlH₄ or NaBH₄) and Grignard reaction with carbonyl compounds. Phenols are obtained from cumene (isopropylbenzene) via cumene hydroperoxide intermediate or by nucleophilic substitution of aryl halides with aqueous NaOH at high temperature and pressure (Dow process). Ethers are best prepared by Williamson synthesis: alkoxide ion (from sodium + alcohol) reacts with primary alkyl halide via SN2 mechanism. Dehydration of alcohols at 413 K with conc. H₂SO₄ also yields ethers (intermolecular) or alkenes (intramolecular) depending on temperature. NCERT Example 7.3 walks through the mechanism of Williamson synthesis, a favourite MCQ topic.

Alcohols and phenols are polar due to the -OH group and exhibit extensive hydrogen bonding, leading to higher boiling points than hydrocarbons and ethers of comparable molar mass. For instance, ethanol (C₂H₅OH) boils at 351 K while dimethyl ether (CH₃OCH₃, same molecular formula) boils at 248 K. Lower alcohols (up to C₃) are completely miscible with water due to hydrogen bonding; solubility decreases with chain length as the hydrophobic alkyl part dominates. Phenols are weakly acidic (pKₐ ~ 10) because the phenoxide ion is resonance-stabilised; alcohols are almost neutral (pKₐ ~ 16). Ortho-substituted phenols like ortho-nitrophenol show intramolecular hydrogen bonding, lowering boiling point and water solubility compared to para-isomers. Ethers lack hydrogen bonding among themselves but can accept hydrogen bonds from water, giving limited solubility. NCERT Figure 7.2 illustrates intermolecular vs intramolecular hydrogen bonding.

Alcohols undergo nucleophilic substitution (with HX via SN1 or SN2 depending on alcohol class), dehydration (E1 mechanism catalysed by conc. H₂SO₄ at 443 K to give alkenes), and oxidation. Primary alcohols oxidise to aldehydes (with PCC or mild oxidising agents) or carboxylic acids (with strong oxidising agents like KMnO₄). Secondary alcohols oxidise to ketones; tertiary alcohols resist oxidation. Lucas test differentiates 1°, 2°, 3° alcohols based on rate of formation of alkyl chloride with ZnCl₂/HCl — tertiary alcohols react immediately (turbidity), secondary in 5-10 minutes, primary do not react at room temperature. Esterification with carboxylic acids (Fischer esterification using conc. H₂SO₄ catalyst) is reversible and follows nucleophilic acyl substitution mechanism. NCERT reaction 7.19 details the mechanism of dehydration; NCERT Exercise 7.10 tests oxidation products.

Phenols are weakly acidic; they react with sodium hydroxide to form sodium phenoxide but not with sodium bicarbonate (unlike carboxylic acids). The -OH group activates the benzene ring towards electrophilic substitution (ortho and para directing due to +M effect), making phenol highly reactive. Bromination occurs with bromine water at room temperature to give 2,4,6-tribromophenol (white precipitate), a standard test for phenol. Nitration with dilute HNO₃ yields o- and p-nitrophenol; with conc. HNO₃ it gives 2,4,6-trinitrophenol (picric acid). Kolbe reaction (CO₂ under pressure on sodium phenoxide) produces salicylic acid (o-hydroxybenzoic acid), precursor of aspirin. Reimer-Tiemann reaction (CHCl₃ + NaOH) introduces a formyl group at ortho position, yielding salicylaldehyde. NCERT Section 7.5 covers these reactions with mechanisms.

Ethers are relatively unreactive due to the inert C-O-C linkage but undergo cleavage with hot concentrated HI or HBr. Reaction mechanism depends on ether structure: methyl ethers give methyl iodide and the corresponding alcohol; mixed ethers follow SN2 pathway with iodide attacking the less hindered carbon. Aryl alkyl ethers like anisole cleave to give phenol and alkyl halide because C(aryl)-O bond is stronger than C(alkyl)-O bond. Ethers are distinguished from alcohols by Lucas test (alcohols react, ethers do not) and sodium metal test (alcohols liberate hydrogen, ethers do not). Victor Meyer test distinguishes 1°, 2°, 3° alcohols based on colour of nitroso product after treatment with nitrous acid. Hinsberg test uses benzenesulfonyl chloride to differentiate 1°, 2°, 3° amines; it does not apply to alcohols or ethers. NCERT in-text question 7.11 often becomes an MCQ on ether cleavage products.

CBSE introduced assertion-reason format in 2021; each MCQ presents two statements and four answer codes. Both assertion (A) and reason (R) may be true, but R must be the correct explanation of A to choose option (A). Common traps include true statements that are unrelated or R being a general fact not explaining A. Chapter 7 yields classic assertion-reason pairs: 'A: Ethanol has higher boiling point than ethoxyethane. R: Ethanol forms intermolecular hydrogen bonds.' (Correct answer: Both true, R explains A). Another: 'A: Phenol is more acidic than ethanol. R: Phenoxide ion is resonance stabilised.' HOTS questions test application across chapters, e.g. 'Why is phenol a weaker acid than benzoic acid?' requires understanding electron-withdrawing effect of -COOH vs electron-donating effect of -OH on conjugate base stability. NCERT Exercise 7.20 and 7.21 are prime HOTS sources.

Memorising reactions is not enough; you need instant doubt resolution when a mechanism does not click at 11 PM before the exam. CBSETUTOR.ai provides a 24×7 AI tutor accessible via mobile app or web. Snap a photo of any MCQ from your coaching worksheet or NCERT Exercise — the AI explains the correct answer, common errors, and cross-links to related reactions. The platform hosts 500+ chapter-wise MCQs for Class 12 Chemistry, auto-graded with performance analytics. You can filter by difficulty (Easy/Medium/Hard), by topic (Preparation/Reactions/Tests), and even by previous year board paper frequency. At ₹999/month flat fee covering all subjects from Class 6 to 12, it is far more affordable than weekend crash courses that charge ₹5,000 for a single chapter. Parents in cities like Pune and Jaipur report their children solving 50 MCQs/day on CBSETUTOR.ai during February revision, leading to 8-10 mark improvements in organic chemistry sections. Start your 3-day free trial, upload the trickiest assertion-reason MCQ from this page and experience AI-powered learning that adapts to your pace.

Section A of the CBSE Class 12 Chemistry paper contains 16 MCQs (1 mark each), of which roughly 2-3 come from Alcohols, Phenols and Ethers. Time allocation: 20 minutes for all 16, so you have ~75 seconds per MCQ. Read the question stem carefully — underline keywords like 'major product,' 'immediate,' 'does not react.' Eliminate obviously wrong options first; often two choices are clearly incorrect, leaving a 50-50 guess if needed. For assertion-reason MCQs, verify A and R independently before checking if R explains A; many students lose marks by not reading option codes carefully. If a mechanism-based MCQ stumps you, skip and return after attempting easier questions — do not let one MCQ cost you time for three easier ones. In nomenclature MCQs, double-check IUPAC priority rules: lowest locant to functional group, alphabetical order of substituents, correct suffix (-ol, -oic acid). For numerical or product-prediction MCQs, jot down a quick one-line reaction on the margin; this prevents silly errors and helps in review if time permits. Mark answers on the OMR sheet in batches of five to save time and reduce bubbling errors. CBSETUTOR.ai's MCQ module has a timer and mimics OMR interface so you practise under exam conditions.