Hello,Welcome to StudentBro.
Hello,Welcome to StudentBro.
Hello,Welcome to StudentBro.
Aldehydes and ketones are important classes of organic compounds containing the carbonyl (-C=O) functional group. They play a significant role in biological processes, pharmaceuticals, and industrial applications. Aldehydes have the carbonyl group at the end of the carbon chain, whereas ketones have it within the chain. Understanding their structure, preparation, properties, and reactions is crucial for NEET aspirants.
Aldehydes contain a -CHO functional group and follow the general formula R-CHO.
Aliphatic Aldehydes – Contain open-chain structures (e.g., Formaldehyde, Acetaldehyde).
Aromatic Aldehydes – Contain a benzene ring attached to the -CHO group (e.g., Benzaldehyde).
Ketones contain a C=O group bonded to two carbon atoms and follow the general formula R-CO-R'.
Simple Ketones – Both R groups are the same (e.g., Acetone).
Mixed Ketones – Different R groups are attached to the carbonyl carbon (e.g., Methyl Ethyl Ketone).
Aldehydes: Named by replacing the -e in the parent hydrocarbon with -al (e.g., Ethanal for CH₃CHO).
Ketones: Named by replacing -e in the parent hydrocarbon with -one (e.g., Propanone for CH₃COCH₃).
Aldehydes: Named by adding the suffix -aldehyde (e.g., Acetaldehyde for CH₃CHO).
Ketones: Named by indicating the alkyl groups followed by ketone (e.g., Dimethyl Ketone for CH₃COCH₃).
From Alcohols – Oxidation of primary alcohols using PCC or KMnO₄.
From Alkenes – Ozonolysis of alkenes followed by reduction.
From Acid Chlorides – Rosenmund reduction using hydrogen and palladium catalyst.
From Nitriles – Reduction of nitriles using SnCl₂/HCl.
From Alcohols – Oxidation of secondary alcohols using PCC or KMnO₄.
From Alkenes – Ozonolysis of alkenes leading to ketone formation.
From Acyl Chlorides – Reaction with organocadmium compounds.
From Nitriles – Reduction of nitriles using Grignard reagents.
Boiling Points – Higher than hydrocarbons due to dipole interactions but lower than alcohols (no hydrogen bonding).
Solubility – Soluble in water due to hydrogen bonding with water molecules; higher members are insoluble.
Odor – Lower aldehydes have a pungent smell, while ketones are relatively less odorous.
Addition of HCN – Forms cyanohydrins.
Addition of Grignard Reagents – Forms alcohols after hydrolysis.
Addition of Alcohols – Forms hemiacetals and acetals in aldehydes.
Aldehydes Oxidation – Converts aldehydes into carboxylic acids (KMnO₄, Tollens’ test).
Ketones Oxidation – Oxidizes under strong conditions to form carboxylic acids.
Reduction to Alcohols – Aldehydes reduce to primary alcohols, ketones to secondary alcohols (NaBH₄, LiAlH₄).
Reduction to Hydrocarbons – Clemmensen reduction (Zn/HCl) and Wolff-Kishner reduction (NH₂NH₂/KOH).
Aldehydes and ketones with α-hydrogen undergo aldol condensation in the presence of a base, forming β-hydroxy aldehydes or ketones.
Aldehydes without α-hydrogen undergo disproportionation in the presence of a strong base, forming an alcohol and a carboxylic acid.
Methyl ketones react with iodine and NaOH to form iodoform (CHI₃), a yellow precipitate.
Aldehydes react with Tollens’ reagent (AgNO₃/NH₃) to form a silver mirror.
Ketones do not respond to this test.
Aldehydes react with Fehling’s solution to form a red precipitate of Cu₂O.
Ketones do not react.
Ketones with a CH₃CO- group react with iodine and NaOH to form a yellow iodoform precipitate.
Aldehydes do not give this test.
Formaldehyde – Used in disinfectants, resins, and plastics.
Acetaldehyde – Used in the synthesis of acetic acid and perfumes.
Acetone – Common solvent in nail polish removers and industrial cleaning.
Methyl Ethyl Ketone (MEK) – Used in the production of synthetic rubber and plastics.
Aldehydes and ketones are fundamental organic compounds with vast applications in industry and biological systems. Understanding their classification, preparation, properties, and reactions is essential for NEET aspirants, as they frequently appear in competitive exams.
