Introduction to Aldehydes, Ketones, and Carboxylic Acids

Aldehydes, ketones, and carboxylic acids are essential topics in NEET Organic Chemistry. These compounds contain carbonyl or carboxyl functional groups and exhibit distinct chemical behavior.

• Aldehydes (R-CHO): Carbonyl group attached to at least one hydrogen.

• Ketones (R-CO-R’): Carbonyl group bonded to two carbon atoms.

• Carboxylic acids (R-COOH): Carbonyl group bonded to a hydroxyl group.

Understanding these compounds is important for NEET because they are frequently tested in reactions, functional group identification, and mechanism-based questions.

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Nomenclature

Aldehydes:

• Replace “-e” of the parent alkane with “-al”.

  • Example: CH3CHO → Ethanal

Ketones:

• Replace “-e” of the parent alkane with “-one”.

  • Example: CH3COCH3 → Propanone

Carboxylic Acids:

• Replace “-e” of the parent alkane with “-oic acid”.

  • Example: CH3COOH → Ethanoic acid

Proper IUPAC nomenclature is frequently tested in NEET MCQs.

Physical Properties

• Boiling Points: Carboxylic acids > Alcohols > Aldehydes/Ketones due to hydrogen bonding.

• Solubility: Aldehydes and ketones are moderately soluble; carboxylic acids are highly soluble in water.

• Odor: Lower aldehydes and ketones are pungent; carboxylic acids have sour smell.

• State: Lower members are liquids; higher members may be solids.

Physical properties are linked with polarity, hydrogen bonding, and molecular weight, which is important for NEET conceptual questions.

Chemical Properties of Aldehydes and Ketones

1. Nucleophilic Addition Reactions

   • Carbonyl carbon is electrophilic, reacts with nucleophiles.

   • Common reactions:

     • Formation of cyanohydrins

     • Reaction with Grignard reagents forming alcohols

     • Addition of H2O, alcohols, or amines

2. Oxidation Reactions

   • Aldehydes are easily oxidized to carboxylic acids.

   • Ketones resist oxidation unless strong oxidizing agents are used.

3. Reduction Reactions

   • Both aldehydes and ketones reduce to primary and secondary alcohols respectively.

4. Special Reactions

   • Aldehydes undergo Tollens’, Fehling’s, and Benedict’s tests (positive for aldehydes).

   • Ketones generally do not give these tests.

NEET questions often focus on reaction type, products, and distinguishing tests.

Chemical Properties of Carboxylic Acids

1. Acidity

   • Carboxylic acids are weak acids, forming carboxylate ions in solution.

   • Stabilization of the carboxylate ion explains their acidity.

2. Reactions with Bases

   • Forms salts: R-COOH + NaOH → R-COONa + H2O

3. Reduction

   • Reduced to primary alcohols using LiAlH4.

4. Substitution Reactions

   • Acid reacts with alcohols to form esters (esterification).

   • Reacts with SOCl2 to form acid chlorides.

NEET questions often focus on functional group reactions, acidity, and derivatives.

Mechanisms to Focus On

• Nucleophilic addition in aldehydes/ketones (mechanism-based MCQs).

• Acid-catalyzed esterification of carboxylic acids.

• Oxidation of aldehydes to acids.

Understanding mechanisms helps in reasoning-based NEET questions.

Comparison Table

Comparison helps NEET students quickly differentiate reactivity and properties.

Applications

1. Aldehydes: Formaldehyde used in resins, disinfectants, and plastics.

2. Ketones: Acetone used as solvent and nail polish remover.

3. Carboxylic Acids: Acetic acid used in vinegar, food preservatives, and chemical synthesis.

Linking reactions and properties to applications strengthens conceptual understanding.

Tips for NEET Students

1. Focus on functional group identification and reactions.

2. Learn distinguishing tests for aldehydes and ketones.

3. Revise mechanisms for nucleophilic addition and esterification.

4. Use tables and flowcharts to remember acidity, oxidation, and reduction trends.

5. Relate applications with structure and reactions for better retention.

Conclusion

Aldehydes, Ketones, and Carboxylic Acids are high-yield topics in NEET Organic Chemistry. By mastering structure, physical and chemical properties, reactions, and applications, students can confidently answer a variety of NEET questions.

At StudentBro.in, we provide concise, exam-focused notes for NEET 2026 aspirants, enabling them to revise efficiently, strengthen conceptual clarity, and perform better in exams.