NCERT Class 12 Chemistry Chemistry-II: Chapter 2 — Alcohols, Phenols and Ethers
This chapter, Alcohols, Phenols and Ethers, is the second chapter in the NCERT Class 12 Chemistry textbook. It introduces students to the nomenclature, preparation, and properties of these important organic compounds. The chapter details the classification of alcohols based on the number of hydroxyl groups (mono-, di-, polyhydric) and the hybridization of the carbon atom attached to the -OH group (sp3 and sp2 hybridized carbons). It further categorizes sp3 hybridized alcohols into primary, secondary, and tertiary, as well as allylic and benzylic alcohols. Phenols are defined as compounds with -OH groups directly attached to aromatic systems, while ethers are formed by replacing the hydrogen of the -OH group with an alkyl or aryl group. The chapter aims to provide a systematic understanding of these compounds, highlighting their relevance in everyday life and industry, and preparing students for advanced organic chemistry concepts.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 12 |
| Subject | Chemistry |
| Book | Chemistry-II |
| Chapter | Chapter 2 — Alcohols, Phenols and Ethers |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 4 minutes |
| Word count | 611 |
Learning outcomes
- Name alcohols, phenols, and ethers using IUPAC nomenclature.
- Discuss methods for preparing alcohols from alkenes, aldehydes, ketones, and carboxylic acids.
- Explain the preparation of phenols from haloarenes, benzene sulphonic acids, diazonium salts, and cumene.
- Describe the synthesis of ethers from alcohols and from alkyl halides/sodium alkoxides/aryloxides.
- Correlate the physical properties of alcohols, phenols, and ethers with their structures.
- Analyze the chemical reactions of alcohols, phenols, and ethers based on their functional groups.
Vocabulary
| Word | Meaning |
|---|---|
| Alcohols | Organic compounds containing one or more hydroxyl (–OH) groups directly attached to an aliphatic carbon atom. |
| Phenols | Organic compounds containing one or more hydroxyl (–OH) groups directly attached to an aromatic system. |
| Ethers | Organic compounds formed by replacing the hydrogen atom of the hydroxyl group of an alcohol or phenol by an alkyl or aryl group. |
| Monohydric | Alcohols or phenols containing one hydroxyl group. |
| Dihydric | Alcohols or phenols containing two hydroxyl groups. |
| Polyhydric | Alcohols or phenols containing many hydroxyl groups. |
| sp3 hybridised carbon | A carbon atom involved in four single bonds. |
| Allylic carbon | An sp3 hybridised carbon atom adjacent to a carbon-carbon double bond. |
| Benzylic carbon | An sp3 hybridised carbon atom adjacent to an aromatic ring. |
| Primary alcohol | An alcohol where the -OH group is attached to a primary carbon atom. |
| Secondary alcohol | An alcohol where the -OH group is attached to a secondary carbon atom. |
| Tertiary alcohol | An alcohol where the -OH group is attached to a tertiary carbon atom. |
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Practice questions
- What is the difference between an alcohol and a phenol? Answer: In alcohols, the -OH group is attached to an aliphatic carbon atom, while in phenols, it is attached to an aromatic carbon atom.
- Classify alcohols based on the number of hydroxyl groups. Answer: Alcohols can be classified as monohydric (one -OH group), dihydric (two -OH groups), or polyhydric (many -OH groups).
- What is an allylic alcohol? Answer: An allylic alcohol is one where the -OH group is attached to an sp3 hybridised carbon atom adjacent to a carbon-carbon double bond.
- How are ethers formed? Answer: Ethers can be formed by substituting the hydrogen atom of the hydroxyl group of an alcohol or phenol by an alkyl or aryl group.
Practice MCQs
Q1. Which of the following is an example of a phenol?
Explanation: Phenol has a hydroxyl group directly attached to an aromatic ring (benzene ring).
Q2. A compound with the formula CH3OCH3 is classified as:
Explanation: CH3OCH3, dimethyl ether, fits the general structure of an ether (R-O-R').
Q3. Which type of alcohol has the -OH group attached to a tertiary carbon atom?
Explanation: Tertiary alcohols are defined by the -OH group being bonded to a carbon atom that is itself bonded to three other carbon atoms.
Q4. In an allylic alcohol, the -OH group is attached to:
Explanation: Allylic alcohols specifically have the -OH group on an sp3 carbon next to a double bond.
Q5. Which of the following is a polyhydric alcohol?
Explanation: Ethylene glycol (ethane-1,2-diol) has two -OH groups, making it a dihydric alcohol, a type of polyhydric alcohol.
Frequently asked questions
What is the main difference between alcohols and phenols?
Alcohols have a hydroxyl (-OH) group attached to an aliphatic carbon atom, whereas phenols have the -OH group directly attached to an aromatic carbon atom.
How are ethers structurally different from alcohols?
Ethers have an oxygen atom bonded to two alkyl or aryl groups (R-O-R'), while alcohols have a hydroxyl group (-OH) attached to an alkyl or aryl group (R-OH).
What does 'polyhydric' mean in the context of alcohols?
Polyhydric alcohols are compounds that contain more than two hydroxyl (-OH) groups in their structure.
What is a benzylic alcohol?
A benzylic alcohol is an alcohol where the -OH group is attached to a saturated carbon atom (sp3 hybridized) that is next to an aromatic ring.
Why is the classification of alcohols important?
Classification helps in systematically studying their properties, reactions, and applications, making the subject of organic chemistry more manageable.
What are the key applications mentioned for alcohols, phenols, and ethers?
Alcohols are basic compounds for detergents, phenols for antiseptics, and ethers for fragrances.
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NCERT Class 12 Chemistry — Chemistry-II — Chapter 2 — Alcohols, Phenols and Ethers. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.