NCERT Class 12 Chemistry Chemistry-II: Chapter 3 — Aldehydes, Ketones and Carboxylic Acids
This chapter, "Aldehydes, Ketones and Carboxylic Acids," is a crucial part of the NCERT Class 12 Chemistry curriculum. It delves into organic compounds featuring the carbonyl group (>C=O), which is fundamental in organic chemistry and found in various materials like fabrics, flavors, plastics, and drugs. The chapter covers the nomenclature and structure of aldehydes, ketones, and carboxylic acids, explaining their common and IUPAC naming systems. It details methods for preparing these compounds and explores their characteristic reactions. Students will learn to correlate the physical properties and chemical behaviors of these functional groups with their structures. The chapter also touches upon the mechanisms of selected reactions, the factors influencing the acidity of carboxylic acids, and their overall significance in biochemical processes and industrial applications. This unit is essential for understanding a wide range of organic molecules and their roles in everyday life and scientific advancements.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 12 |
| Subject | Chemistry |
| Book | Chemistry-II |
| Chapter | Chapter 3 — Aldehydes, Ketones and Carboxylic Acids |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 3 minutes |
| Word count | 485 |
Learning outcomes
- Write common and IUPAC names of aldehydes, ketones, and carboxylic acids.
- Describe the structures of compounds containing carbonyl and carboxyl groups.
- Explain important methods of preparation and reactions of these compound classes.
- Correlate physical properties and chemical reactions with their structures.
- Understand factors affecting the acidity of carboxylic acids and their reactions.
- Recognize the uses of aldehydes, ketones, and carboxylic acids.
Vocabulary
| Word | Meaning |
|---|---|
| Carbonyl group | A functional group consisting of a carbon atom double-bonded to an oxygen atom (>C=O). |
| Aldehyde | A compound containing a carbonyl group bonded to a carbon atom and a hydrogen atom. |
| Ketone | A compound containing a carbonyl group bonded to two carbon atoms. |
| Carboxylic acid | A compound containing a carboxyl group (-COOH), where the carbonyl carbon is bonded to a hydroxyl group. |
| Nomenclature | The system of naming chemical compounds. |
| IUPAC names | Systematic names for chemical compounds established by the International Union of Pure and Applied Chemistry. |
| Common names | Informal names for chemical compounds, often derived from their source or properties. |
| Functional group | A specific group of atoms within a molecule responsible for the characteristic chemical reactions of that molecule. |
| Biochemical processes | Chemical reactions that occur within living organisms. |
| Solvents | Substances that dissolve other substances. |
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Practice questions
- What is the difference between an aldehyde and a ketone based on their structure? Answer: In aldehydes, the carbonyl group is bonded to at least one hydrogen atom, while in ketones, the carbonyl group is bonded to two carbon atoms.
- How are the common names of most aldehydes derived? Answer: The common names of most aldehydes are derived from the common names of the corresponding carboxylic acids by replacing the ending '-ic' with 'aldehyde'.
- What is the functional group present in carboxylic acids? Answer: The functional group present in carboxylic acids is the carboxyl group (-COOH).
- Give an example of a compound that adds fragrance to nature and belongs to the aldehyde family. Answer: Vanillin (from vanilla beans), salicylaldehyde (from meadow sweet), and cinnamaldehyde (from cinnamon) are examples.
Practice MCQs
Q1. Which functional group is central to the compounds discussed in this chapter?
Explanation: The chapter focuses on organic compounds containing the carbon-oxygen double bond (>C=O), which is known as the carbonyl group.
Q2. In ketones, the carbonyl group is bonded to:
Explanation: Ketones are defined by the carbonyl group being attached to two carbon atoms.
Q3. The common name of an aldehyde is derived from the corresponding carboxylic acid by replacing '-ic' with:
Explanation: The nomenclature rule states that the ending '-ic' of the carboxylic acid name is replaced by 'aldehyde' to form the common name of the aldehyde.
Q4. Which of the following is a derivative of carboxylic acids?
Explanation: Amides, acyl halides, esters, and anhydrides are mentioned as derivatives of carboxylic acids in the text.
Q5. Vanillin, known for its pleasant fragrance, is an example of:
Explanation: The text explicitly mentions vanillin as an example of an aldehyde that adds fragrance to nature.
Frequently asked questions
What are the main classes of organic compounds discussed in NCERT Class 12 Chemistry Chapter 3?
The main classes are Aldehydes, Ketones, and Carboxylic Acids, all characterized by the carbonyl group or carboxyl group.
What is the significance of the carbonyl group in organic chemistry?
The carbonyl group (>C=O) is one of the most important functional groups, found in compounds that are constituents of fabrics, flavorings, plastics, and drugs.
How do common names of aldehydes relate to carboxylic acids?
The common names of most aldehydes are derived from the common names of the corresponding carboxylic acids by replacing the ending '-ic' with 'aldehyde'.
What is the difference between aldehydes and ketones in terms of bonding?
In aldehydes, the carbonyl carbon is bonded to at least one hydrogen atom, while in ketones, it is bonded to two carbon atoms.
Besides aldehydes and ketones, what other related compounds are mentioned?
Carboxylic acids, amides, acyl halides, esters, and anhydrides are also discussed as related compounds or derivatives.
Where are aldehydes, ketones, and carboxylic acids found in nature?
They are widespread in the plant and animal kingdom and play important roles in biochemical processes, adding fragrance and flavor to nature.
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NCERT Class 12 Chemistry — Chemistry-II — Chapter 3 — Aldehydes, Ketones and Carboxylic Acids. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.