Aldehydes, Ketones & Carboxylic Acids - Concept Based Problems - Identifying Compounds Based On Tests

Slide 1: Aldehydes, Ketones & Carboxylic Acids - Concept Based Problems - Identifying compounds based on tests

Introduction to aldehydes, ketones, and carboxylic acids
Importance and applications of these compounds
Types of tests used to identify these compounds

Slide 2: Identifying aldehydes

Selective oxidation of aldehydes to carboxylic acids using Tollens’ reagent
Formation of silver mirror on the inner wall of the test tube
Example: Identification of formaldehyde using Tollens’ test

Slide 3: Identifying ketones

Ketones do not give positive results for Tollens’ test
Ketones undergo nucleophilic addition reactions with nucleophiles like Grignard reagent
Example: Identification of acetone using Grignard reaction

Slide 4: Formation of carboxylic acids

Carboxylic acids are formed by the oxidation of primary alcohols and aldehydes
Strong oxidizing agents like potassium permanganate and chromic acid are used
Example: Oxidation of ethanol to acetic acid using potassium permanganate

Slide 5: Tests for carboxylic acids

Carboxylic acids are acidic in nature and react with bases to form salts
Effervescence is observed when carboxylic acids react with carbonates and bicarbonates
Example: Identification of acetic acid using sodium carbonate

Slide 6: Silver nitrate test for carboxylic acids

Carboxylic acids react with silver nitrate to form silver salts
Cloudiness or precipitation of the silver salt is observed
Example: Identification of benzoic acid using silver nitrate test

Slide 7: Acidified potassium dichromate test

Carboxylic acids are oxidized by acidified potassium dichromate to form carbon dioxide and water
Change in color of the solution from orange to green is observed
Example: Identification of formic acid using acidified potassium dichromate test

Slide 8: Functional group tests

Chemical tests to identify the functional groups present in organic compounds
Examples: Fehling’s test for aldehydes, iodoform test for methyl ketones, haloform test for methyl ketones containing α-hydrogens

Slide 9: Reaction with sodium hydrogen carbonate

Carboxylic acids react with sodium hydrogen carbonate to produce carbon dioxide, water, and salt
Effervescence and the formation of a salt can be observed
Example: Identification of acetic acid using sodium hydrogen carbonate

Slide 10: Summary

Aldehydes, ketones, and carboxylic acids can be identified by specific chemical tests
Tollens’ reagent for aldehydes, Grignard reagent for ketones, and various tests for carboxylic acids
Understanding the reactions and properties of these compounds is crucial for organic chemistry.

Slide 11: Reactions of Aldehydes

Aldehydes undergo oxidation reactions to form carboxylic acids
Tollens’ reagent and Fehling’s solution are commonly used to oxidize aldehydes
Reduction of aldehydes forms primary alcohols
Example: Oxidation of ethanol to acetaldehyde using Tollens’ reagent

Slide 12: Reactions of Ketones

Ketones do not undergo oxidation reactions as easily as aldehydes
Reduction of ketones forms secondary alcohols
Nucleophilic addition reactions are common for ketones
Example: Reduction of acetone to isopropanol using sodium borohydride

Slide 13: Reactions of Carboxylic Acids

Carboxylic acids can undergo esterification reactions with alcohols
Acyl chlorides react with alcohols to form esters
Decarboxylation reactions convert carboxylic acids to alcohols
Example: Esterification of acetic acid with ethanol to form ethyl acetate

Slide 14: Substitution Reactions of Carboxylic Acids

Carboxylic acids can undergo substitution reactions with nucleophiles
Sulphonation reactions with sulphuric acid and acylation reactions with acyl chlorides are common
Example: Reaction of benzoic acid with thionyl chloride to form benzoyl chloride

Slide 15: Nucleophilic Acyl Substitution Reactions

Nucleophilic acyl substitution reactions involve the replacement of the acyl group in the carboxylic acid by a nucleophile
Nucleophiles can be any electron-rich species such as an amine or alcohol
Example: Reaction of acetic acid with ammonia to form ammonium acetate

Slide 16: Reactions of Carboxylic Acid Derivatives

Carboxylic acid derivatives include esters, amides, acid chlorides, and anhydrides
Ester hydrolysis produces a carboxylic acid and an alcohol
Amide hydrolysis produces a carboxylic acid and an amine
Example: Hydrolysis of ethyl acetate to form acetic acid and ethanol

Slide 17: Physical Properties of Aldehydes, Ketones, and Carboxylic Acids

Aldehydes and ketones have lower boiling points than carboxylic acids
Carboxylic acids have higher boiling points due to hydrogen bonding
Solubility in water increases as the number of carbons in the molecule decreases
Example: Solubility comparison of acetic acid, acetone, and benzaldehyde

Slide 18: Chemical Properties of Aldehydes, Ketones, and Carboxylic Acids

Aldehydes and ketones undergo nucleophilic addition reactions
Carboxylic acids are weak acids and undergo acid-base reactions
Oxidation reactions are common for aldehydes and primary alcohols
Example: Oxidation of benzaldehyde to benzoic acid using potassium permanganate

Slide 19: Common Applications of Aldehydes, Ketones, and Carboxylic Acids

Aldehydes are used as preservatives, flavoring agents, and in the production of polymers
Ketones find application as solvents, pharmaceuticals, and in the production of plastics
Carboxylic acids are used in food preservation, drug formulation, and as intermediates in organic syntheses
Example: Use of acetic acid in vinegar production

Slide 20: Summary and Key Takeaways

Aldehydes, ketones, and carboxylic acids have distinct chemical properties and reactions
They can be identified through specific tests such as Tollens’ reagent, Grignard reaction, and silver nitrate test
Understanding the reactions and properties of these compounds is essential for their applications in various industries
Reviewing and practicing these concepts will help in mastering the topic.

Slide 21: Oxidation of Aldehydes and Ketones

Aldehydes can be oxidized to carboxylic acids using strong oxidizing agents like potassium permanganate or chromic acid
Ketones are relatively resistant to oxidation reactions due to the absence of the hydrogen atom bonded to the carbonyl carbon
Example: Oxidation of formaldehyde to formic acid using potassium permanganate

Slide 22: Reduction of Aldehydes and Ketones

Aldehydes and ketones can be reduced to form alcohols using reducing agents like sodium borohydride or lithium aluminum hydride
Reduction of aldehydes and ketones occurs through the addition of hydrogen to the carbonyl group
Example: Reduction of acetone to isopropanol using sodium borohydride

Slide 23: Esterification Reactions of Carboxylic Acids

Carboxylic acids can react with alcohols in the presence of an acid catalyst to form esters
This esterification reaction involves the loss of water molecule (dehydration)
Example: Formation of ethyl acetate from acetic acid and ethanol

Slide 24: Amide Formation from Carboxylic Acids

Carboxylic acids react with amines to form amides
This reaction involves the substitution of the hydroxyl group in the carboxylic acid by the amine group
Example: Formation of acetamide from acetic acid and ammonia

Slide 25: Hydrolysis of Esters

Esters can be hydrolyzed to form carboxylic acids and alcohols in the presence of an acid or base
Acid-catalyzed ester hydrolysis forms carboxylic acids and alcohols
Base-catalyzed ester hydrolysis forms carboxylate ions and alcohols
Example: Hydrolysis of ethyl acetate to form acetic acid and ethanol

Slide 26: Fischer Esterification

Fischer esterification is the reaction between a carboxylic acid and an alcohol in the presence of an acid catalyst to form an ester
The reaction involves the combination of the carboxylic acid’s hydroxyl group and the alcohol’s hydroxyl group, followed by elimination of water
Example: Fischer esterification of acetic acid with methanol to form methyl acetate

Slide 27: Fischer Esterification Mechanism

Fischer esterification mechanism involves several steps including protonation, nucleophilic attack, and elimination of water
The mechanism proceeds through an intermediate called acylium ion
Example: Mechanism of Fischer esterification between acetic acid and methanol

Slide 28: Acid-Base Properties of Carboxylic Acids

Carboxylic acids are weak acids due to the presence of the carboxyl group (–COOH)
They can donate a proton (H+) to a base and form carboxylate ions
The equilibrium between the acid and its conjugate base makes carboxylic acids weak acids
Example: Dissociation of acetic acid in water to form acetate ion and a hydronium ion

Slide 29: Acidity Comparison of Carboxylic Acids

The acidity of carboxylic acids depends on the stability of the carboxylate ion formed after losing a proton
Electron-withdrawing groups attached to the carboxyl group increase acidity
Examples: Comparison of acetic acid and benzoic acid acidity and the effect of electron-withdrawing groups

Slide 30: Applications of Carboxylic Acids

Carboxylic acids are widely used in various industries and applications
They are used as food preservatives, flavoring agents, and in the production of soaps and detergents
They are also used in pharmaceuticals, cosmetics, and as intermediates in organic synthesis
Example: Use of salicylic acid in the production of aspirin and benzoic acid as a food preservative