CBSE Class 12 Chemistry Chapter 22: Alcohols, Phenols, and Ethers NCERT Solutions

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NCERT Solutions PDF Class 12 PDF

CBSE Class 12 Chemistry Chapter 11, Alcohols, Phenols, and Ethers, introduces students to these vital organic compounds. The NCERT Solutions offer a clear path to understanding their nomenclature, structures, and properties. You'll learn to confidently name diverse alcohols, phenols, and ethers using IUPAC rules and to draw their structures from given names. The solutions present numerous examples, solidifying your grasp of nomenclature principles and improving your ability to visualize molecular arrangements. This chapter is key to building a robust foundation in organic chemistry, essential for both exam success and further studies. By working through these solutions, you'll sharpen your problem-solving abilities and gain confidence in tackling related topics.

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BoardCBSE
ClassClass 12
SubjectChemistry
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 22

Chapter summary

Chapter 22 of the NCERT Class 12 Chemistry syllabus focuses on Alcohols, Phenols, and Ethers. This section provides detailed solutions for exercises related to the IUPAC nomenclature of these compounds. Students will practice naming complex structures and drawing structures from given names, covering alcohols, phenols, and ethers. The solutions aim to clarify the systematic naming conventions and structural representations essential for organic chemistry.

Learning outcomes

  • Understand the IUPAC nomenclature rules for alcohols, phenols, and ethers.
  • Write IUPAC names for given structures of alcohols, phenols, and ethers.
  • Draw the chemical structures corresponding to given IUPAC names.
  • Identify and differentiate between alcohols, phenols, and ethers based on their structures.
  • Apply nomenclature rules to complex organic molecules containing multiple functional groups.

Topics covered

Paper topics

  • IUPAC Nomenclature of Alcohols
  • IUPAC Nomenclature of Phenols
  • IUPAC Nomenclature of Ethers
  • Structure Drawing from IUPAC Names
  • Functional Group Identification
  • Alkyl Group Naming
  • Aryl Group Naming
  • Substituent Naming
  • Parent Chain Identification
  • Locant Assignment

Important topics

  • IUPAC Nomenclature of Alcohols
  • IUPAC Nomenclature of Phenols
  • IUPAC Nomenclature of Ethers
  • Structure Drawing from IUPAC Names
  • Parent Chain Identification
  • Locant Assignment

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Questions and Solutions

Question 11.1

Write IUPAC names of the following compounds:

(i) CH_3

CH_3 - CH - CH - CH_3

| |

CH_3 OH

(ii)

H_3C - CH - CH_2 - CH - CH - CH_2 - CH_3

| | |

OH OH C_2H_5

(iii)

CH_3 - CH - CH - CH_3

| |

OH OH

(iv)

HO - CH_2 - CH - CH_2 - OH | OH (v) CH_3 | CH_3 - C - CH_3 | OH

(vi)

CH_3 | CH_3 - CH - CH_2 - CH_3 | OH

(vii)

CH_3 | CH_3 - CH - CH_2 - CH - CH_3

| |

OH CH_3

(viii)

CH_3 | CH_3 - CH - CH - CH_3

| |

OH CH_3

(ix)

CH_3 - CH_2 - O - CH - CH_2 - CH_3 | CH_3 (x) C_6H_5 - O - C_2H_5

(xi)

C_6H_5 - O - CH_2 - CH_2 - CH_2 - CH_2 - CH_2 - CH_2 - CH_3

(xii)

CH_3 - CH_2 - O - CH - CH_2 - CH_3 | CH_3

Solution:

To determine the IUPAC names, we follow the systematic rules of organic nomenclature:

  1. (i) The longest carbon chain containing the hydroxyl group has 5 carbons (pentane). The hydroxyl group is on the third carbon. There are two methyl groups on the second carbon and one methyl group on the fourth carbon. However, the longest chain containing the -OH group is the pentane chain. Let's re-examine the structure. The longest chain containing the -OH group is 5 carbons long. The -OH group is on carbon 3. There are two methyl groups on carbon 2 and one methyl group on carbon 4. The correct longest chain is 5 carbons. The -OH is on C3. There are two methyl groups on C2 and one on C4. The correct IUPAC name is 2,2,4-Trimethylpentan-3-ol.

  2. (ii) The longest carbon chain has 7 carbons (heptane). There is an ethyl group (C2H5) on carbon 5 and hydroxyl groups on carbons 2 and 4. The IUPAC name is 5-Ethylheptane-2,4-diol.

  3. (iii) The longest carbon chain has 4 carbons (butane). There are hydroxyl groups on the second and third carbons. The IUPAC name is Butane-2,3-diol.

  4. (iv) The longest carbon chain has 3 carbons (propane). There are hydroxyl groups on carbons 1, 2, and 3. The IUPAC name is Propane-1,2,3-triol.

  5. (v) This is a phenol derivative. The hydroxyl group is directly attached to the benzene ring. The methyl group is at the ortho position (position 2) relative to the hydroxyl group. The IUPAC name is 2-Methylphenol.

  6. (vi) This is a phenol derivative. The hydroxyl group is directly attached to the benzene ring. The methyl group is at the para position (position 4) relative to the hydroxyl group. The IUPAC name is 4-Methylphenol.

  7. (vii) This is a phenol derivative. The hydroxyl group is directly attached to the benzene ring. There are methyl groups at positions 2 and 5. The IUPAC name is 2,5-Dimethylphenol.

  8. (viii) This is a phenol derivative. The hydroxyl group is directly attached to the benzene ring. There are methyl groups at positions 2 and 6. The IUPAC name is 2,6-Dimethylphenol.

  9. (ix) This is an ether. The oxygen atom is attached to a methyl group and a 2-methylpropyl group. The longest chain attached to oxygen is the 2-methylpropyl group (isobutyl group). The oxygen is attached to the first carbon of this chain. The IUPAC name treats the CH3O- group as a methoxy substituent. The parent chain is propane. The structure is CH3-CH(CH3)-CH2-O-CH3. The longest chain is 3 carbons. The methoxy group is on C1. There is a methyl group on C2. The IUPAC name is 1-Methoxy-2-methylpropane.

  10. (x) This is an ether. The oxygen atom is attached to a phenyl group (C6H5) and an ethyl group (C2H5). The phenyl group is treated as a substituent on the ethoxy chain. The IUPAC name is Ethoxybenzene.

  11. (xi) This is an ether. The oxygen atom is attached to a phenyl group (C6H5) and a straight-chain heptyl group (C7H15). The phenyl group is treated as a substituent on the heptoxy chain. The IUPAC name is 1-Phenoxyheptane.

  12. (xii) This is an ether. The oxygen atom is attached to an ethyl group (CH3CH2-) and a sec-butyl group (CH3-CH(CH3)-CH2-). The longest chain attached to oxygen is the sec-butyl group. The oxygen is attached to the second carbon of this 4-carbon chain. The IUPAC name treats the ethyl group as an ethoxy substituent. The parent chain is butane. The ethoxy group is on carbon 2. The IUPAC name is 2-Ethoxybutane.

Question 11.2

Write structures of the compounds whose IUPAC names are as follows:

(i) 2-Methylbutan-2-ol

Solution:

To draw the structure for 2-Methylbutan-2-ol, we break down the IUPAC name:

  • Butan-2-ol: This indicates a parent chain of 4 carbon atoms (butane) with a hydroxyl (-OH) group attached to the second carbon atom.
  • 2-Methyl: This indicates that a methyl (-CH3) group is also attached to the second carbon atom.

Combining these parts, we construct the structure:

CH_3 - C(OH)(CH_3) - CH_2 - CH_3

The structure has a central carbon atom bonded to a methyl group, a hydroxyl group, an ethyl group, and another methyl group. This is indeed 2-Methylbutan-2-ol.

Common mistakes

  • Incorrectly identifying the parent carbon chain.
  • Misplacing locants for substituents or functional groups.
  • Confusing numbering priorities in complex molecules.
  • Errors in naming ethers, especially with complex alkyl or aryl groups.
  • Failing to account for all substituents when naming.

Revision tips

  • Practice drawing structures from names and vice versa repeatedly.
  • Create flashcards with common functional groups and their IUPAC naming prefixes/suffixes.
  • Focus on identifying the longest carbon chain containing the principal functional group.
  • Review the rules for numbering the carbon chain to give the lowest locants.
  • Work through all examples in the chapter to ensure comprehensive understanding.

Practice MCQs

Q1. What is the IUPAC name for the compound with the structure CH3-CH(OH)-CH(OH)-CH3?

Q2. Which IUPAC name correctly describes the structure C6H5-O-C2H5?

Q3. The IUPAC name for HO-CH2-CH(OH)-CH2-OH is:

Q4. What is the IUPAC name for a phenol with a methyl group at position 4?

Q5. Which structure corresponds to 2-Methylbutan-2-ol?

Frequently asked questions

What is the main focus of Chapter 22 NCERT Solutions for Class 12 Chemistry?

The main focus is on the IUPAC nomenclature of Alcohols, Phenols, and Ethers. It includes writing IUPAC names for given structures and drawing structures from given IUPAC names.

How do these solutions help in understanding organic chemistry?

These solutions provide clear, step-by-step explanations for naming organic compounds, reinforcing the systematic rules of IUPAC nomenclature and helping students visualize molecular structures.

Are the questions in the solutions exactly the same as in the NCERT textbook?

Yes, the questions are preserved exactly as they appear in the NCERT textbook, ensuring that students are practicing with the official material. The wording of the questions may be expanded for clarity.

What is the difference between an alcohol and a phenol?

In alcohols, the hydroxyl (-OH) group is attached to an aliphatic carbon atom, while in phenols, the hydroxyl group is directly attached to an aromatic ring carbon atom.

How are ethers named using IUPAC nomenclature?

Ethers are named as alkoxyalkanes. The smaller alkyl group along with the oxygen atom is considered as the alkoxy substituent (e.g., methoxy, ethoxy) attached to the parent alkane chain derived from the larger alkyl group.

Can these solutions be used for quick revision before exams?

Yes, these solutions are ideal for revision as they offer concise explanations and cover all the essential nomenclature rules and examples from the chapter.

Important links

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