Organic compounds containing oxygen play a very important role in our daily life. In Class 12 Chemistry, the chapter “Alcohols, Phenols and Ethers Class 12 Notes” is one of the most scoring and concept-based chapters. Questions from this chapter are frequently asked in CBSE board exams, competitive exams, and school tests.
In this chapter, we study:
- Alcohols – compounds containing –OH group attached to carbon
- Phenols – –OH group attached directly to benzene ring
- Ethers – oxygen atom connected to two alkyl or aryl groups
These notes explain each topic, formula, reaction, and mechanism (Alcohol Phenol and Ether Class 12 Notes) in detail so that students can easily understand and revise before exams. ✅
Alcohol Phenol and Ether Class 12 Notes | CBSE Chemistry Full Explanation & Important Questions
🔹 Classification of Alcohols
Alcohols are organic compounds containing hydroxyl group (–OH) attached to a saturated carbon atom.
1️⃣ Based on Number of –OH Groups
(a) Monohydric Alcohols
Contain one –OH group
Example:
- Methanol (CH₃OH)
- Ethanol (C₂H₅OH)
(b) Dihydric Alcohols
Contain two –OH groups
Example:
- Ethylene glycol (HO–CH₂–CH₂–OH)
(c) Trihydric Alcohols
Contain three –OH groups
Example:
- Glycerol (HO–CH₂–CHOH–CH₂–OH)
2️⃣ Based on Nature of Carbon Atom
(a) Primary (1°) Alcohol
–OH attached to carbon connected to one alkyl group
Example: Ethanol (CH₃CH₂OH)
(b) Secondary (2°) Alcohol
–OH attached to carbon connected to two alkyl groups
Example: Isopropyl alcohol
(c) Tertiary (3°) Alcohol
–OH attached to carbon connected to three alkyl groups
Example: tert-Butyl alcohol
🔹 Nomenclature of Alcohols
- Replace –e of alkane with –ol
Example:
Ethane → Ethanol
Propane → Propanol
Numbering is done so that –OH gets the lowest number.
🔹 Preparation of Alcohols
1️⃣ From Alkenes (Hydration)
Acid-catalyzed hydration
Alkene + H₂SO₄ → Alcohol
Example:
CH₂=CH₂ + H₂O → CH₃CH₂OH
✔ Follows Markovnikov’s rule
2️⃣ From Alkyl Halides
Using aqueous KOH or NaOH
R–X + KOH → R–OH + KX
3️⃣ From Aldehydes and Ketones
Using reducing agents
- NaBH₄
- LiAlH₄
Aldehyde → Primary alcohol
Ketone → Secondary alcohol
🔹 Physical Properties of Alcohols
- Boiling Point
Alcohols have higher boiling point due to hydrogen bonding - Solubility in Water
Lower alcohols are soluble due to hydrogen bonding
Solubility decreases with increase in carbon chain length
🔹 Chemical Properties of Alcohols
1️⃣ Reaction with Sodium
2R–OH + 2Na → 2R–ONa + H₂↑
✔ Used to detect –OH group
2️⃣ Oxidation of Alcohols
| Type of Alcohol | Oxidation Product |
|---|---|
| Primary | Aldehyde → Acid |
| Secondary | Ketone |
| Tertiary | No oxidation |
Oxidizing agents:
- KMnO₄
- K₂Cr₂O₇
3️⃣ Dehydration of Alcohols
Using conc. H₂SO₄ at 443 K
Alcohol → Alkene + H₂O
🔹 Phenols
🔸 Definition
Phenols are compounds in which –OH group is directly attached to benzene ring.
Example:
C₆H₅OH (Phenol)
🔹 Preparation of Phenol
1️⃣ From Cumene Process
Cumene → Cumene hydroperoxide → Phenol + Acetone
✔ Important industrial method
2️⃣ From Chlorobenzene (Dow’s Process)
Chlorobenzene + NaOH (623 K, 300 atm) → Sodium phenoxide
Acidification → Phenol
🔹 Physical Properties of Phenol
- Colorless crystalline solid
- Higher boiling point due to hydrogen bonding
- Slightly soluble in water
🔹 Chemical Properties of Phenol
1️⃣ Acidic Nature of Phenol
Phenol is weakly acidic due to resonance stabilization of phenoxide ion.
Reaction with NaOH:
C₆H₅OH + NaOH → C₆H₅ONa + H₂O
2️⃣ Electrophilic Substitution Reactions
(a) Nitration
Phenol + dilute HNO₃ → o-nitrophenol + p-nitrophenol
(b) Halogenation
Phenol + Br₂ water → 2,4,6-tribromophenol (white ppt)
3️⃣ Kolbe’s Reaction
Sodium phenoxide + CO₂ → Salicylic acid
4️⃣ Reimer–Tiemann Reaction
Phenol + CHCl₃ + NaOH → Salicylaldehyde
🔹 Ethers
🔸 Definition
Ethers are compounds in which oxygen is connected to two alkyl or aryl groups.
General formula:
R–O–R′
Example:
Diethyl ether (C₂H₅–O–C₂H₅)
🔹 Nomenclature of Ethers
- Name alkyl groups in alphabetical order + ether
Example:
CH₃–O–C₂H₅ → Ethyl methyl ether
🔹 Preparation of Ethers
1️⃣ Williamson Ether Synthesis
R–ONa + R′–X → R–O–R′ + NaX
✔ Best method for preparing ethers
✔ SN2 reaction
2️⃣ Dehydration of Alcohols
2R–OH → R–O–R + H₂O
Occurs at 413 K using conc. H₂SO₄
🔹 Physical Properties of Ethers
- Pleasant smell
- Low boiling point
- Slightly soluble in water
🔹 Chemical Properties of Ethers
1️⃣ Reaction with HI
R–O–R′ + HI → R–I + R′–OH
At excess HI:
R–I + R′–I
🔹 Differences Between Alcohol, Phenol and Ether
| Property | Alcohol | Phenol | Ether |
|---|---|---|---|
| –OH group | Present | Present | Absent |
| Acidic nature | Very weak | Weak acid | Neutral |
| Hydrogen bonding | Strong | Strong | Weak |
🔹 Important Formulas & Reactions (Quick Revision)
- Alcohol + Na → Sodium alkoxide
- Phenol + Br₂ water → 2,4,6-tribromophenol
- Ether + HI → Alkyl iodide
- Oxidation of alcohol → Aldehyde / Ketone
Below are Important Questions & Repeated Questions from the chapter
Alcohol Phenol and Ether Class 12 Notes
🔥 Important & Repeated Questions
🔹 1️⃣ Very Short Answer Questions (1 Mark)
- What is the general formula of alcohols?
- Why do alcohols have higher boiling points than alkanes?
- Name the functional group present in alcohols and phenols.
- Write the IUPAC name of CH₃–CH₂–OH.
- Which alcohol does not undergo oxidation easily?
- Why is phenol acidic in nature?
- Write the chemical formula of phenol.
- What is Williamson ether synthesis?
- Write one use of ethanol.
- Which type of alcohol gives aldehyde on oxidation?
✔ Repeated in Board Exams
🔹 2️⃣ Short Answer Questions (2 Marks)
- Distinguish between primary, secondary and tertiary alcohols with one example each.
- Why are phenols more acidic than alcohols? Explain briefly.
- Write the reaction of alcohol with sodium metal.
- Why is ether considered relatively unreactive?
- Write the structure of ethyl methyl ether.
- What happens when phenol reacts with bromine water?
- Write the chemical equation for dehydration of ethanol.
- Give two physical properties of alcohols.
- Write one method of preparation of phenol.
- What is hydrogen bonding? How does it affect boiling point?
✔ Frequently Repeated
🔹 3️⃣ Short Answer Questions (3 Marks)
- Explain the acidic nature of phenol with resonance structures.
- Write the mechanism of dehydration of ethanol.
- Describe the oxidation reactions of primary and secondary alcohols.
- Explain Williamson ether synthesis with example.
- Write three differences between alcohols and phenols.
- What happens when ethyl ether is heated with excess HI?
- Describe the preparation of phenol from chlorobenzene.
- Why tertiary alcohols do not undergo oxidation easily?
- Explain the solubility of alcohols in water.
- Write the mechanism of Kolbe’s reaction.
✔ Board-Based Questions
🔹 4️⃣ Long Answer Questions (5 Marks)
- Describe the preparation, physical and chemical properties of alcohols.
- Explain the preparation and chemical reactions of phenol in detail.
- Discuss the preparation, properties and reactions of ethers.
- Explain the following reactions:
- Kolbe’s reaction
- Reimer–Tiemann reaction
- Williamson ether synthesis
- Give a detailed comparison between alcohol, phenol and ether.
- Explain why phenol is more acidic than ethanol.
- Write the chemical tests to distinguish between alcohol, phenol and ether.
✔ Highly Repeated in CBSE Exams
🔹 5️⃣ Assertion – Reason Questions (Repeated Pattern)
- Assertion (A): Phenol is acidic in nature.
Reason (R): Phenoxide ion is stabilized by resonance. - Assertion (A): Ethers have lower boiling points than alcohols.
Reason (R): Ethers do not form hydrogen bonds. - Assertion (A): Tertiary alcohols do not undergo oxidation.
Reason (R): They do not have α-hydrogen.
✔ Important for Objective Section
🔹 6️⃣ Case-Based / Competency-Based Questions
- A compound reacts with sodium metal releasing hydrogen gas.
(a) Identify the functional group
(b) Write the reaction
(c) Name the compound - Phenol gives white precipitate with bromine water.
(a) Name the product
(b) Write the balanced equation
(c) State the type of reaction
✔ New Exam Pattern Focus
🔹 7️⃣ Most Repeated Reactions to Remember
- Alcohol + Na → Sodium alkoxide + H₂
- Phenol + Br₂ water → 2,4,6-Tribromophenol
- Phenol + NaOH → Sodium phenoxide
- Ether + HI → Alkyl iodide
- Dehydration of alcohol → Alkene
🔹 Conclusion (Exam Tip)-Alcohol Phenol and Ether Class 12 Notes
If you prepare these important & repeated questions along with reactions and mechanisms, you can easily score maximum marks from the chapter Alcohol Phenol and Ether in Class 12 Chemistry. 🎯📖