Carboxylic Acids and Their Derivatives – NEET Chemistry Class 12

Carboxylic acids and their derivatives are organic compounds containing the –COOH group and its functional derivatives like esters, acid chlorides, anhydrides, and amides. This chapter is crucial for NEET because it covers acidity, nucleophilic acyl substitution, and reaction mechanisms.

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Introduction to Carboxylic Acids

• Definition: Organic compounds containing one or more –COOH groups.

• General Formula: R–COOH

• Importance: Carboxylic acids are reactive due to polar carbonyl and hydroxyl groups, making them key in both laboratory and biological chemistry.

Nomenclature

• IUPAC Names: Suffix –oic acid (e.g., Ethanoic acid, Propanoic acid)

• Common Names: Based on source or trivial names (e.g., Acetic acid, Formic acid)

• Derivatives: Named based on functional group:

  • Esters: –oate (e.g., Methyl ethanoate)

  • Acid chlorides: –oyl chloride (e.g., Ethanoyl chloride)

  • Amides: –amide (e.g., Ethanamide)

  • Anhydrides: –anhydride (e.g., Ethanoic anhydride)

Physical Properties

• Carboxylic Acids:

  • Hydrogen bonding → higher boiling points than alcohols

  • Soluble in water, especially lower members due to H-bonding

• Derivatives:

  • Esters: Pleasant odor, lower boiling point than acids

  • Acid chlorides: Reactive, moisture-sensitive

  • Amides: High boiling points due to H-bonding

Chemical Properties

1. Acidity:

   • Carboxylic acids ionize to form R–COO⁻

   • Acidity decreases with electron-donating groups, increases with electron-withdrawing groups

2. Reactions of Carboxylic Acids:

   • Formation of acid chlorides, esters, amides, anhydrides

   • Reduction to primary alcohols (LiAlH₄)

   • Decarboxylation reactions

3. Reactions of Derivatives:

   • Nucleophilic acyl substitution is common

   • Acid chlorides react with water, alcohols, ammonia to form corresponding derivatives

   • Esters undergo hydrolysis (acidic or basic) to give carboxylic acids

Mechanisms and Reactivity

• Nucleophilic Acyl Substitution: Key reaction for carboxylic acid derivatives

  • Nucleophile attacks carbonyl carbon → tetrahedral intermediate → substitution of leaving group

• Reactivity order: Acid chloride > Anhydride > Ester > Amide

Importance for NEET Preparation

• Questions often involve reaction products, mechanisms, acidity, and comparative reactivity.

• Esters and amides are frequently asked in identification and synthetic applications.

• Acidity trends and nucleophilic substitution mechanisms are high-yield topics in NEET exams.

Previous Year NEET Questions – Insights

• Hydrolysis of esters and amides

• Formation of derivatives from carboxylic acids

• Acidity and resonance stabilization in carboxylates

• Reduction of carboxylic acids to alcohols

• Mechanism-based questions involving nucleophilic acyl substitution

Study Tips for Students

1. Memorize Nomenclature Rules – Acids and derivatives

2. Practice Reaction Mechanisms – Nucleophilic acyl substitution, esterification, reduction, decarboxylation

3. Understand Physical Properties – Boiling points, solubility, H-bonding

4. Refer NCERT Examples – NEET often uses NCERT-based reactions

5. Solve Previous Year Questions – Helps reinforce mechanisms, trends, and reaction outcomes

Conclusion

Mastering Carboxylic Acids and Their Derivatives is essential for NEET success. It allows students to predict reaction products, solve mechanism-based questions, and understand acidity trends confidently. A strong understanding ensures high scoring potential in Class 12 organic chemistry.