Alcohol, Ether and Phenol Notes for Class 12, JEE and NEET: Preparation, Reactions and Tests
eSaral Academic and Editorial Team
Summary
Alcohol, Ether and Phenol notes for Class 12 cover the NCERT chapter Alcohols, Phenols and Ethers: classification, preparation, physical properties, reactions, acidity, name reactions (Williamson, Kolbe, Reimer–Tiemann) and tests to distinguish the compounds. This page gives reaction tables, solved examples and handwritten notes for CBSE boards, JEE and NEET.
Alcohol, Ether and Phenol notes work best as a reaction-by-reaction revision sheet. In the current NCERT Class 12 Chemistry book, the chapter Alcohols, Phenols and Ethers is Unit 7 of 10. Older books number it Chapter 11, so some websites and notes still use the old number. The CBSE syllabus focuses on primary alcohols for chemical properties, so check the latest syllabus for what is required in the boards.
Alcohol, Ether and Phenol Notes: Classification and Structure
Compound | General formula | Feature |
|---|---|---|
Alcohol | R–OH | –OH on an sp³ carbon. Primary (1°), secondary (2°) or tertiary (3°) |
Phenol | Ar–OH | –OH on a benzene ring carbon (sp²) |
Ether | R–O–R′ | Oxygen between two alkyl or aryl groups |
Alcohols and ethers with the same formula are functional isomers (for example, ethanol and methoxymethane).
Preparation in Alcohol, Ether and Phenol Notes
Preparation of Alcohols
Method | Reaction | Note |
|---|---|---|
Acid-catalysed hydration of alkenes | Alkene + H₂O (H⁺) → alcohol | Follows Markovnikov’s rule |
Hydroboration–oxidation | Alkene → alcohol (B₂H₆, then H₂O₂/NaOH) | Anti-Markovnikov product |
Reduction of aldehydes and ketones | Aldehyde → 1° alcohol, ketone → 2° alcohol (NaBH₄ or LiAlH₄) | |
Reduction of carboxylic acids | RCOOH → 1° alcohol (LiAlH₄) | |
Grignard reagent with carbonyl compounds | HCHO → 1° alcohol, other aldehydes → 2° alcohols, ketones → 3° alcohols | Followed by hydrolysis |
Preparation of Phenols
- From haloarenes: chlorobenzene with NaOH at about 623 K and high pressure, followed by acidification.
- From benzenesulphonic acid: fusion with NaOH, followed by acidification.
- From diazonium salts: warming with water, or with dilute acid.
- Cumene process (industrial): cumene is oxidised to cumene hydroperoxide, which gives phenol and acetone.
Preparation of Ethers
- Dehydration of alcohols: with conc. H₂SO₄ at 413 K. This works for primary alcohols.
- Williamson ether synthesis: R–ONa + R′–X → R–O–R′ + NaX. It is an SN2 reaction, so a primary alkyl halide must be used. Secondary and tertiary halides give an alkene by elimination.
Physical Properties in Alcohol, Ether and Phenol Notes
- Boiling point: alcohols and phenols have much higher boiling points than ethers, alkanes and haloalkanes of similar mass, because they form hydrogen bonds. Among isomeric alcohols, the boiling point decreases as branching increases: 1° > 2° > 3°.
- Solubility: lower alcohols are soluble in water because of hydrogen bonding with water, and the solubility decreases as the alkyl chain gets longer.
- Ethers: have low boiling points, similar to alkanes of comparable mass, because they cannot form hydrogen bonds with each other.
Chemical Reactions of Alcohols in Alcohol, Ether and Phenol Notes
Reaction | Reagent and result |
|---|---|
Acidic character | Alcohol + Na → sodium alkoxide + H₂. Acidity: 1° > 2° > 3° |
Esterification | Alcohol + carboxylic acid (conc. H₂SO₄) → ester + water |
With HX (Lucas test) | Alcohol + HCl/ZnCl₂ → alkyl chloride. Reactivity: 3° > 2° > 1° |
With PCl₅, PCl₃ or SOCl₂ | Alcohol → alkyl chloride. SOCl₂ is preferred, because the by-products (SO₂ and HCl) are gases |
Dehydration | Conc. H₂SO₄ at 443 K → alkene. At 413 K → ether (for primary alcohols). Ease: 3° > 2° > 1° |
Oxidation | 1° alcohol → aldehyde (PCC) → carboxylic acid (KMnO₄ or K₂Cr₂O₇). 2° alcohol → ketone. 3° alcohols resist oxidation |
Dehydrogenation (Cu, 573 K) | 1° → aldehyde, 2° → ketone, 3° → alkene |
Lucas Test to Distinguish Alcohols
Alcohol type | Observation with Lucas reagent (ZnCl₂ + conc. HCl) |
|---|---|
Tertiary | Turbidity appears immediately |
Secondary | Turbidity appears in about 5 minutes |
Primary | No turbidity at room temperature |
Tertiary alcohols react fastest because they form the most stable carbocation (SN1 mechanism).
Chemical Reactions of Phenols in Alcohol, Ether and Phenol Notes
Acidity of Phenol
Phenol (pKa about 10) is more acidic than water (about 15.7), and water is more acidic than alcohols (about 16–18). Phenol is more acidic because the phenoxide ion is stabilised by resonance, with the negative charge spread over the ring. Electron-withdrawing groups (such as –NO₂ at the ortho or para position) increase the acidity, and electron-donating groups (such as –CH₃) decrease it. Phenol reacts with NaOH, but it is not acidic enough to liberate CO₂ from NaHCO₃.
Electrophilic Substitution in Phenol
The –OH group activates the ring and directs incoming groups to the ortho and para positions.
Reaction | Conditions and product |
|---|---|
Nitration | Dilute HNO₃ → o- and p-nitrophenol. Conc. HNO₃ → 2,4,6-trinitrophenol (picric acid) |
Halogenation | Br₂ in CS₂ at low temperature → o- and p-bromophenol. Br₂ water → 2,4,6-tribromophenol (white precipitate) |
Kolbe’s reaction | Sodium phenoxide + CO₂ (400 K, 4–7 atm), then H⁺ → salicylic acid |
Reimer–Tiemann reaction | Phenol + CHCl₃ + NaOH, then H⁺ → salicylaldehyde |
Other reactions of phenol: reaction with zinc dust gives benzene, oxidation with chromic acid gives benzoquinone, and neutral FeCl₃ gives a violet colour (a test for phenols).
Chemical Reactions of Ethers in Alcohol, Ether and Phenol Notes
- Cleavage by HI: R–O–R′ + HI → R–OH + R′–I. With a primary or secondary alkyl group, the iodide attacks the smaller alkyl group (SN2). With a tertiary alkyl group, the tertiary alkyl iodide is formed (SN1). Anisole with HI gives phenol and methyl iodide.
- Electrophilic substitution in aromatic ethers: the –OR group is activating and directs to the ortho and para positions, as in halogenation, nitration and Friedel–Crafts reactions of anisole.
Important Name Reactions and Tests in Alcohol, Ether and Phenol Notes
Name | Reaction |
|---|---|
Williamson synthesis | Alkoxide + primary alkyl halide → ether |
Kolbe’s reaction | Sodium phenoxide + CO₂ → salicylic acid |
Reimer–Tiemann reaction | Phenol + CHCl₃ + NaOH → salicylaldehyde |
Lucas test | Distinguishes 1°, 2° and 3° alcohols |
FeCl₃ test | Phenols give a violet colour |
Bromine water test | Phenol gives a white precipitate of 2,4,6-tribromophenol |
Cumene process | Cumene → phenol + acetone |
Solved Examples from Alcohol, Ether and Phenol Notes
Q1. Arrange in the increasing order of acidity: ethanol, water, phenol, p-nitrophenol.
Ethanol < water < phenol < p-nitrophenol. The –NO₂ group increases the acidity by withdrawing electrons and stabilising the phenoxide ion.
Q2. Which alcohol gives turbidity immediately with Lucas reagent: butan-1-ol, butan-2-ol or 2-methylpropan-2-ol?
2-Methylpropan-2-ol, because it is a tertiary alcohol and forms a stable tertiary carbocation.
Q3. What is formed when anisole reacts with HI?
Phenol and methyl iodide. The iodide attacks the methyl group (SN2), because the phenyl–oxygen bond does not break.
Q4. Why is a primary alkyl halide used in the Williamson synthesis?
An alkoxide is a strong base, so with a secondary or tertiary halide it eliminates to give an alkene. A primary halide undergoes SN2 substitution to give the ether.
India's Best Exam Preparation for Class 12th - Download Now
India's Best Exam Preparation for Class 12th - Download Now
India's Best Exam Preparation for Class 12th - Download Now
India's Best Exam Preparation for Class 12th - Download Now
India's Best Exam Preparation for Class 12th - Download Now
India's Best Exam Preparation for Class 12th - Download Now
.
India's Best Exam Preparation for Class 12th - Download Now
India's Best Exam Preparation for Class 12th - Download Now
India's Best Exam Preparation for Class 12th - Download Now
Common Mistakes in Alcohol, Ether and Phenol Problems
Mistake | Correct approach |
|---|---|
Using a secondary or tertiary halide in the Williamson synthesis | Use a primary alkyl halide, because other halides eliminate |
Mixing up the dehydration temperatures | 443 K gives an alkene and 413 K gives an ether (for primary alcohols) |
Thinking that phenol reacts with NaHCO₃ | Phenol reacts with NaOH only. Carboxylic acids react with NaHCO₃. |
Forgetting that tertiary alcohols do not oxidise easily | 1° gives aldehyde, 2° gives ketone, and 3° resists oxidation |
Cleaving the aryl–oxygen bond in anisole with HI | The O–CH₃ bond breaks, and phenol is formed |
How to Study Alcohol, Ether and Phenol Notes for Exams
- Read the NCERT chapter first. Download it from eSaral’s NCERT Class 12 books page.
- Solve the textbook questions with eSaral’s NCERT Solutions for Class 12 Chemistry Chapter 7.
- Learn the reactions from the Alcohol, Ether and Phenol notes in groups: preparation, acidity, oxidation, electrophilic substitution and name reactions. Write each reaction with its reagent and condition.
- For JEE, practise mechanism-based questions, such as why phenol is more acidic than ethanol, and why tertiary alcohols react fastest in the Lucas test. For NEET, practise recall of reagents and products.
Frequently Asked Questions
What is the acidity order of alcohols, phenols and water?
Phenol (pKa about 10) is more acidic than water (about 15.7), which is more acidic than alcohols (about 16–18). Phenol is more acidic because of the resonance stabilisation of the phenoxide ion. This order is a common question in JEE Main and NEET, and it is part of eSaral’s Alcohol, Ether and Phenol notes.
Why does a tertiary alcohol react fastest in the Lucas test?
The Lucas reagent (ZnCl₂ and conc. HCl) converts an alcohol into an alkyl chloride. Tertiary alcohols form the most stable carbocation (SN1 mechanism), so the solution turns turbid immediately. Secondary alcohols take about 5 minutes, and primary alcohols give no turbidity at room temperature.
What is the Williamson ether synthesis, and why must a primary alkyl halide be used?
It is an SN2 reaction between a sodium alkoxide and an alkyl halide to give an ether. With a secondary or tertiary halide, the strongly basic alkoxide causes elimination (E2) and gives an alkene instead of an ether. The Alcohol, Ether and Phenol notes on this page show the reaction.
What are the conditions for the dehydration of alcohols to give an alkene or an ether?
Both use an alcohol and conc. H₂SO₄. At 443 K, intramolecular dehydration gives an alkene. At 413 K, intermolecular dehydration gives an ether, and this works well for primary alcohols. Temperature decides the product.
How does the –OH group in phenol direct electrophilic substitution?
The –OH group donates electron density to the ring by resonance, so it activates the ring and directs incoming groups to the ortho and para positions. For example, bromine water gives 2,4,6-tribromophenol without a catalyst, while Br₂ in CS₂ at low temperature gives mainly o- and p-bromophenol.
Which chapter is Alcohols, Phenols and Ethers in Class 12 Chemistry?
In the current NCERT Class 12 Chemistry book, it is Unit 7 of 10. Older books call it Chapter 11. Check the contents page of your edition, and follow the chapter name. These Alcohol, Ether and Phenol notes use the current numbering.
How do you distinguish between phenol and alcohol?
In Alcohol, Ether and Phenol notes, the usual tests are as follows: phenol gives a violet colour with neutral FeCl₃, a white precipitate with bromine water, and it reacts with NaOH. An alcohol does not give these results. Ethanol also reacts with sodium to give hydrogen, as phenol does, so use the FeCl₃ test to separate them.
What happens when anisole reacts with HI?
Anisole gives phenol and methyl iodide, because the iodide ion attacks the methyl group in an SN2 reaction. The aryl–oxygen bond does not break.
Where can I find notes and solutions for this chapter on eSaral?
eSaral has handwritten Alcohol, Ether and Phenol notes on this page, the NCERT book for Class 12 and step-by-step NCERT solutions for the chapter, all linked on this page.
Team eSaral
eSaral Academic and Editorial Team
Team eSaral is the collective author profile for educational content created by eSaral’s teachers and academic contributors. The team draws on expertise from IIT graduates, doctors, experienced educators and subject specialists to develop resources for JEE, NEET and school students. Our articles aim to explain concepts clearly and help students study with confidence.
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