Aldehydes, Ketones, and Carboxylic Acids Class 12 Chemistry PDF

Class 12 Chemistry: Aldehydes, Ketones, and Carboxylic Acids 1. Introduction Aldehydes, Ketones, and Carboxylic Acids are important classes of organic compounds. They contain the carbonyl group (C=O) and exhibit unique physical and chemical properties. This chapter covers their nomenclature, prep...

Class 12 Chemistry: Aldehydes, Ketones, and Carboxylic Acids 1. Introduction Aldehydes, Ketones, and Carboxylic Acids are important classes of organic compounds. They contain the carbonyl group (C=O) and exhibit unique physical and chemical properties. This chapter covers their nomenclature, preparation, properties, reactions, and applications. 2. Detailed Explanation 2.1 Aldehydes: Organic compounds with the -CHO functional group. Example: Methanal (Formaldehyde), Ethanal (Acetaldehyde). 2.2 Ketones: Organic compounds with a C=O group bonded to two alkyl or aryl groups. Example: Propanone (Acetone), Butanone. 2.3 Carboxylic Acids: Organic acids containing the -COOH group. Example: Methanoic acid (Formic acid), Ethanoic acid (Acetic acid). 3. Reaction Mechanisms Aldol Condensation: Involves the enolate ion of one molecule attacking the carbonyl group of another. Forms beta-hydroxy aldehydes/ketones, followed by dehydration to alpha, beta-unsaturated carbonyl compounds. Cannizzaro Reaction: Disproportionation reaction of non-enolizable aldehydes to alcohol and carboxylic acid in a basic medium. HVZ Reaction: Substitution of the alpha-hydrogen of carboxylic acids with a halogen using red phosphorus and halogen. Clemmensen Reduction: Reduces aldehydes/ketones to alkanes using Zn(Hg) in HCl. Wolff-Kishner Reduction: Converts aldehydes/ketones to alkanes using hydrazine and KOH. 4. Important Conversions Some key conversions include: 1. Ethanol to Acetic Acid: Ethanol is oxidized with acidified KMnO4 to acetic acid. 2. Benzaldehyde to Benzoic Acid: Oxidation using an oxidizing agent like alkaline KMnO4. 3. Acetone to 2-Propanol: Reduction using NaBH4 or LiAlH4. 5. Important Questions and Answers Q1: Write the mechanism for Aldol Condensation. A1: Step 1: Formation of the enolate ion. Step 2: Nucleophilic attack on the carbonyl group. Step 3: Dehydration to form alpha, beta-unsaturated carbonyl compounds. Q2: Explain the Cannizzaro Reaction with an example. A2: Disproportionation of formaldehyde in the presence of NaOH gives methanol and sodium formate. Q3: How will you convert acetaldehyde to acetic acid? A3: Oxidation of acetaldehyde with acidified KMnO4 or K2Cr2O7 yields acetic acid. Q4: Discuss the acidic nature of carboxylic acids with reasons. A4: Carboxylic acids are acidic due to the stabilization of the carboxylate ion by resonance. Q5: Write a short note on the HVZ reaction. A5: Halogenation of carboxylic acids at the alpha position using red phosphorus and halogens.