Aldehydes Ketones and Carboxylic Acids — Class 12 Chemistry NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 12 Chemistry chapter "Aldehydes Ketones and Carboxylic Acids" — 8 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 12 Chemistry chapter "Aldehydes Ketones and Carboxylic Acids" — 8 important questions with detailed answer…

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Key Questions Covered:

  1. What is the difference between an aldehyde and a ketone? Give structural form…
  2. Explain the mechanism of nucleophilic addition to carbonyl groups. Use the re…
  3. Describe the Aldol condensation reaction. Write the equation for the aldol co…
  4. Explain the oxidation of aldehydes to carboxylic acids. Write the equation fo…
  5. What is a carboxylic acid? Write the IUPAC name of CH3CH2CH2COOH and describe…
  6. Explain the esterification of carboxylic acids. Write the equation for the es…
  7. + 2 more questions in the full chapter

Solutions Summary:

Question Status
What is the difference between an aldehyde and a ketone? … ✓ Solved
Explain the mechanism of nucleophilic addition to carbony… ✓ Solved
Describe the Aldol condensation reaction. Write the equat… ✓ Solved
Explain the oxidation of aldehydes to carboxylic acids. W… ✓ Solved
What is a carboxylic acid? Write the IUPAC name of CH3CH2… ✓ Solved
Explain the esterification of carboxylic acids. Write the… ✓ Solved

Showing 6 of 8 questions

Q1: What is the difference between an aldehyde and a ketone? Give structural formulas and one example of each.

Aldehyde: A compound containing a carbonyl group (C=O) with the carbon bonded to at least one hydrogen atom. The carbonyl carbon is at the end of a carbon chain. General formula: R-CHO or RCHO Example: CH3CHO (acetaldehyde or ethanal) Structural formula: H is always bonded to the carbonyl carbon Ketone: A compound containing a carbonyl group (C=O) where the carbonyl carbon is bonded to two alkyl or aryl groups. The carbonyl carbon is always in the middle of the carbon chain. General formula: R-...

Q2: Explain the mechanism of nucleophilic addition to carbonyl groups. Use the reaction of acetaldehyde with HCN as an example.

Nucleophilic addition mechanism to carbonyl compounds: Reaction: CH3CHO (acetaldehyde) + HCN (hydrogen cyanide) → CH3CH(OH)CN (cyanohydrin) Mechanism (two steps): Step 1: Nucleophilic attack by CN- The CN- ion (from HCN dissociation or formation) acts as a nucleophile. It attacks the electrophilic carbonyl carbon from above or below the C=O plane. The π electrons of C=O move to oxygen, forming a tetrahedral intermediate with negative charge on oxygen. Structure: CH3-CH(-CN)-O- (tetrahedral in...

Q3: Describe the Aldol condensation reaction. Write the equation for the aldol condensation of acetaldehyde.

Aldol condensation: Reaction between two molecules of an aldehyde (or ketone) in the presence of a dilute base, resulting in C-C bond formation. The product is a β-hydroxy aldehyde (aldol) which may further dehydrate to form an α,β-unsaturated aldehyde. Alternative name: Aldol reaction (when the product is an aldol), Aldol condensation (when the product is dehydrated) Reaction of acetaldehyde: 2 CH3CHO + dilute NaOH → CH3CH(OH)CH2CHO (aldol product, 3-hydroxybutanal) Conditions: Dilute base (N...

Q4: Explain the oxidation of aldehydes to carboxylic acids. Write the equation for oxidation of acetaldehyde with Tollens' reagent.

Oxidation of aldehydes to carboxylic acids: Aldehydes are easily oxidized to carboxylic acids (one-step oxidation): R-CHO + [O] → R-COOH Use of Tollens' reagent: Reaction: CH3CHO + 2 Ag(NH3)2+ + H2O → CH3COONH4 + 2 Ag↓ + 3 NH3 + H+ Or written more clearly: CH3CHO + 2 [Ag(NH3)2]+ + 2 OH- → CH3COO- + 2 Ag↓ + 4 NH3 + H2O Tollens' reagent: - Silver ammonia complex: [Ag(NH3)2]+ - Prepared by adding ammonia to AgNO3 solution until the white precipitate of Ag2O dissolves - The product is a clear, c...

Q5: What is a carboxylic acid? Write the IUPAC name of CH3CH2CH2COOH and describe its structure.

Carboxylic acid: An organic compound containing a carboxyl group (-COOH) bonded to a carbon atom. Structure of -COOH group: - Contains a carbonyl group (C=O) bonded to a hydroxyl group (-OH) - The carbon is bonded to the oxygen with a C=O double bond - The same carbon is bonded to -OH with a single bond - General formula: R-COOH where R is an alkyl or aryl group Example: CH3CH2CH2COOH Structure: O || CH3-CH2-CH2-C-OH IUPAC name: Butanoic acid (or butyric acid - common name) Namin...

Q6: Explain the esterification of carboxylic acids. Write the equation for the esterification of acetic acid with ethanol.

Esterification: Reaction between a carboxylic acid and an alcohol to form an ester and water. The reaction is reversible and typically acid-catalyzed. Reaction equation: CH3COOH + C2H5OH ⇌ CH3COOC2H5 + H2O (acetic acid + ethanol → ethyl acetate + water) Conditions: 1. Acid catalyst (usually concentrated H2SO4 or HCl) 2. Heat (reflux or warming) 3. Removal of water (using drying agents like P2O5 or molecular sieves to shift equilibrium forward) Alternative equation showing the reversible natur...

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