JEE Mains Chemistry · Teaching notes
Alcohols, Phenols and Ethers — JEE Mains Chemistry
Alcohols, Phenols and Ethers has 102 past-year questions from 2021 to 2026, and 10 of them ask for a number rather than an option. Three habits carry most of them: rank acidity by how well the ion left behind spreads its negative charge, follow the carbocation whenever an alcohol meets acid and let it shift before the alkene forms, and decide which C–O bond HI breaks, remembering that the aryl–oxygen bond never does. The rest is exact recall, where one swapped reagent costs the mark: which solvent gives which bromophenol, which nitrophenol steam distils, what chloroform and carbon dioxide each put on the ring, and which phenol fails the phthalein test.
Every subtopic, worked example, formula and trap in one printable document — answers shown, ready to share.
Subtopic notes
Classification, Preparation and Physical Properties
13 PYQsAn alcohol is primary, secondary or tertiary by the number of carbons on the carbinol carbon; it is made by hydration, hydroboration, reduction or a Grignard reagent, and hydrogen bonding gives it a far higher boiling point than an ether or alkane of similar mass.
Acidity of Alcohols and Phenols
20 PYQsPhenol is about a million times more acidic than ethanol because the phenoxide ion spreads its charge over the ring; groups that pull electrons, above all nitro groups at ortho and para, make a phenol stronger, and the NaOH, NaHCO₃ and FeCl₃ screens sort compounds by that acidity.
Reactions of Alcohols: Substitution, Dehydration and Rearrangement
15 PYQsAn alcohol reacts at its O–H bond (esters, acetylation) or at its C–O bond once the OH is made a leaving group (halides, Lucas test, dehydration); in acid the carbocation shifts a hydride or methyl to become more stable before the most substituted alkene forms.
Preparation of Phenols and Named Reactions
18 PYQsPhenol is made from chlorobenzene, benzenesulphonic acid, a diazonium salt or cumene, and it is recognised by its named reactions: zinc dust gives benzene, chromic acid gives benzoquinone, Reimer–Tiemann gives salicylaldehyde and Kolbe gives salicylic acid.
Ring Substitution of Phenols and Phenol Tests
17 PYQsThe OH group makes the ring so reactive that bromine water gives 2,4,6-tribromophenol at once while bromine in CS₂ gives mainly p-bromophenol; dilute nitric acid gives o- and p-nitrophenol, concentrated nitric acid gives picric acid, and phthalic anhydride gives phenolphthalein.
Ethers: Williamson Synthesis and Cleavage
19 PYQsEthers are made by the Williamson synthesis, an SN2 reaction of an alkoxide or phenoxide with a methyl or primary halide, and are split by HI or HBr: iodide attacks the smaller alkyl group, a tertiary group leaves as a cation, and the aryl–oxygen bond never breaks.
Formula & revision sheet
10 formulas · 5 reference tables · 34 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
10 formulas · 5 reference tables · 34 gotchas across all subtopics — the exam-eve cheat-sheet
Reference tables (1)
Routes that make alcohols, and routes that do not11 rows
| Route | Reagents | Product | Watch for |
|---|---|---|---|
| Acid hydration of an alkene | Dilute (water, ) | Markovnikov alcohol: | Goes through a carbocation, so methyl and hydride shifts can occur |
| Hydroboration–oxidation | , then | Anti-Markovnikov alcohol: | No carbocation, so no rearrangement |
| Reduction of aldehydes and ketones | , or | Aldehyde → 1° alcohol; ketone → 2° alcohol | Hydrogen adds across the C=O |
| Reduction of acids and esters | or for acids; esters also by over a catalyst | Primary alcohol | leaves a COOH group alone |
| Grignard reagent + carbonyl | RMgX in dry ether, then | HCHO → 1°; RCHO → 2°; → 3° | The new C–C bond forms at the old carbonyl carbon |
| Hydrolysis of an alkyl halide | Aqueous NaOH or KOH | Alcohol with the OH where the halogen was | Aryl halides do not react under these conditions |
| Controlled oxidation of alkanes | , Cu, 523 K, 100 atm; | ; | With methane gives HCHO; with alkanes give acids |
| Methanol from water gas | , , 573–673 K, 200–300 atm | The industrial route to methanol | |
| Fermentation | Sugar with yeast (invertase, then zymase) | Ethanol and | Air must be kept out, or ethanol is oxidised to ethanoic acid |
| Ozonolysis of an alkene | , then Zn and water | Aldehydes and ketones | Never an alcohol: the C=C is cut in two |
| Hydration of an alkyne | Water with | A ketone; ethyne alone gives the aldehyde ethanal | The enol formed first tautomerises; no alcohol survives |
Watch out for (5)
- Acid hydration can move a methyl group→ Routes that make alcohols, and routes that do not
- NaBH₄ does not reduce a carboxylic acid→ Routes that make alcohols, and routes that do not
- Isomers can differ by 80 K→ Classes, common names and boiling points
- Ring carbons count as carbon neighbours→ Classes, common names and boiling points
- The chelated isomer melts lower→ Classes, common names and boiling points
Formulas (2)
Reference tables (1)
Solubility and colour screens with NaOH, NaHCO₃ and FeCl₃4 rows
| Screen | Passes | Fails | Why |
|---|---|---|---|
| Sodium metal ( evolved) | Alcohols, phenols, carboxylic acids | Ethers and alkanes | Sodium replaces the hydrogen of an O–H group |
| Aqueous NaOH (dissolves as a salt) | Phenols, cresols, nitrophenols, carboxylic acids | Alcohols such as cyclohexanol and benzyl alcohol; ethers | Hydroxide removes a proton only from acids stronger than water |
| Aqueous ( evolved) | Carboxylic acids, picric acid, 2,4-dinitrophenol | Phenol, cresols, m- and p-nitrophenol, alcohols | Needs an acid stronger than carbonic acid, pKa below about 6.4 |
| Neutral (colour) | Phenol (violet), salicylic acid, other phenols and enols | Alcohols, benzyl alcohol, anisole | Iron(III) forms a coloured complex with an OH on the ring |
Watch out for (8)
- Lower pKa means the stronger acid→ Why phenol is a stronger acid than an alcohol
- A phenolic O–H uses up a Grignard reagent→ Why phenol is a stronger acid than an alcohol
- Use the molar volume the question gives→ Why phenol is a stronger acid than an alcohol
- Ortho-nitro is not the strongest→ Ranking substituted phenols and alcohols by pKa
- Methoxy at meta makes phenol stronger→ Ranking substituted phenols and alcohols by pKa
- Distance beats electronegativity for −I→ Ranking substituted phenols and alcohols by pKa
- Benzyl alcohol is not a phenol→ Solubility and colour screens with NaOH, NaHCO₃ and FeCl₃
- One nitro group is not enough for bicarbonate→ Solubility and colour screens with NaOH, NaHCO₃ and FeCl₃
Formulas (2)
Watch out for (6)
- Ethanol is primary: no quick Lucas turbidity→ Reactions at the O–H and C–O bonds of alcohols
- Hot copper dehydrates a tertiary alcohol→ Reactions at the O–H and C–O bonds of alcohols
- Acrolein is pungent, not fruity→ Reactions at the O–H and C–O bonds of alcohols
- Check the neighbours before drawing the alkene→ Acid dehydration and carbocation shifts
- A primary alcohol can rearrange too→ Acid dehydration and carbocation shifts
- Acid on an alcohol is Saytzeff; a bulky base on a halide is Hofmann→ Acid dehydration and carbocation shifts
Reference tables (2)
Four ways to make phenol4 rows
| Starting material | Reagents | Intermediate | Products |
|---|---|---|---|
| Chlorobenzene | NaOH, 623 K, about 300 atm; then | Sodium phenoxide | Phenol |
| Benzenesulphonic acid (benzene + oleum) | Fused NaOH; then | Sodium phenoxide | Phenol |
| Aniline | + HCl at 273–278 K; then warm water | Benzenediazonium chloride, | Phenol, and HCl |
| Cumene (isopropylbenzene) | (air); then dilute acid | Cumene hydroperoxide, | Phenol and propanone (acetone) The intermediate is a hydroperoxide (O–O–H), not an alcohol or an ester; acetone is the by-product. |
Named reactions of phenol7 rows
| Reaction | Reagents | Product | Key point |
|---|---|---|---|
| Reduction by zinc dust | Zn, heat | Benzene | Zinc takes the oxygen as ZnO |
| Oxidation | (chromic acid) | Benzo-p-quinone | A conjugated diketone, O=C at C-1 and C-4 |
| Reimer–Tiemann | + aq. NaOH, then | Salicylaldehyde (2-hydroxybenzaldehyde), ortho major | Electrophile ; intermediate is the o-(dichloromethyl)phenoxide, a substituted benzal chloride |
| Kolbe | NaOH; at 400 K, 4–7 atm; then | Salicylic acid (2-hydroxybenzoic acid) | is a weak electrophile, so the phenoxide ion is needed |
| Acetylation | Acetic anhydride or | Phenyl acetate; salicylic acid gives aspirin | Reaction at the O–H, not on the ring |
| Nitration with conc. | Conc. (best via phenol-2,4-disulphonic acid) | Picric acid (2,4,6-trinitrophenol) | A yellow, strongly acidic solid |
| With HCl | Conc. HCl | No reaction: no chlorobenzene | The phenolic C–O bond does not break |
Watch out for (4)
- Hydrolysis of benzal chloride gives benzaldehyde→ Four ways to make phenol
- Multiply step yields, do not add them→ Four ways to make phenol
- Reimer–Tiemann gives the ortho aldehyde as the major product→ Named reactions of phenol
- Chloroform gives the aldehyde, carbon dioxide gives the acid→ Named reactions of phenol
Formulas (2)
Reference tables (1)
The phthalein dye test for phenols4 rows
| Phenol | Position para to OH | Product with phthalic anhydride | Colour in alkali |
|---|---|---|---|
| Phenol | Free | Phenolphthalein | Pink in dilute NaOH; colourless in acid and in excess strong alkali |
| o-Cresol | Free | o-Cresolphthalein | Purple-red |
| p-Cresol | Blocked by | No phthalein dye | No colour The usual answer to 'which phenol gives no colour'. |
| Resorcinol (benzene-1,3-diol) | Free | Fluorescein | Yellow-green fluorescence |
Watch out for (5)
- CS₂ and CHCl₃ both count as low polarity→ Bromination of phenol: the solvent decides
- Count bromine molecules, not bromine atoms→ Bromination of phenol: the solvent decides
- Picric acid is a phenol, not TNT→ Nitration of phenol and picric acid
- Steam carries off the ortho isomer→ Nitration of phenol and picric acid
- Excess alkali removes the pink colour→ The phthalein dye test for phenols
Formulas (3)
Watch out for (6)
- The halide side must be simple→ Making ethers: Williamson synthesis and acid routes
- SN2 does not move the double bond→ Making ethers: Williamson synthesis and acid routes
- A tertiary group reverses the 'smaller group' rule→ Cleaving ethers with HI and HBr
- Phenol is the end of the line→ Cleaving ethers with HI and HBr
- The ring is not a π bond→ Aryl ethers on the ring and in structure proofs
- Para blocked means ortho to the alkoxy group→ Aryl ethers on the ring and in structure proofs
PYQ weightage by concept
15 concepts · 102 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
15 concepts · 102 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Classes, common names and boiling points | 8 | 8% |
| Routes that make alcohols, and routes that do not | 5 | 5% |
| Concept | PYQs | Share |
|---|---|---|
| Ranking substituted phenols and alcohols by pKa | 10 | 10% |
| Why phenol is a stronger acid than an alcohol | 6 | 6% |
| Solubility and colour screens with NaOH, NaHCO₃ and FeCl₃ | 4 | 4% |
| Concept | PYQs | Share |
|---|---|---|
| Acid dehydration and carbocation shifts | 11 | 11% |
| Reactions at the O–H and C–O bonds of alcohols | 4 | 4% |
| Concept | PYQs | Share |
|---|---|---|
| Named reactions of phenol | 11 | 11% |
| Four ways to make phenol | 7 | 7% |
| Concept | PYQs | Share |
|---|---|---|
| Bromination of phenol: the solvent decides | 7 | 7% |
| Nitration of phenol and picric acid | 5 | 5% |
| The phthalein dye test for phenols | 5 | 5% |
| Concept | PYQs | Share |
|---|---|---|
| Cleaving ethers with HI and HBr | 9 | 9% |
| Making ethers: Williamson synthesis and acid routes | 6 | 6% |
| Aryl ethers on the ring and in structure proofs | 4 | 4% |
Test yourself on Alcohols, Phenols and Ethers
20 past JEE Mains questions from this chapter, timed at 48 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.