Chapter 13: Carboxylic Acids

Complete notes for Chapter 13. Covers Carboxylic Acids (Preparation, Reactions), Amino Acids (Classification, Zwitterion, Synthesis), Peptides, and Proteins.

Introduction & Classification

Carboxylic Acids: Contain -COOH group. General formula R-COOH.

Aliphatic: R is alkyl group (e.g., Acetic acid).
Aromatic: -COOH attached to benzene ring (e.g., Benzoic acid).
Fatty Acids: Long chain aliphatic acids (e.g., Palmitic acid C15H31COOH, Stearic acid C17H35COOH). Obtained from fats.

Nomenclature

Common Names: Derived from source. Formic acid (Ants - Formica), Acetic acid (Vinegar - Acetum), Butyric acid (Butter - Butyrum).
IUPAC Names: Alkanoic Acid. (e.g., Methanoic acid, Ethanoic acid).

Preparation of Carboxylic Acids

Oxidation of Primary Alcohols/Aldehydes: With K2Cr2O7/H2SO4.
Hydrolysis of Nitriles: R-CN + H2O/H+ -> R-COOH + NH3.
From Grignard Reagent: R-Mg-X + CO2 -> R-COOMgX -> R-COOH.
Hydrolysis of Esters: R-COOR' + NaOH -> R-COONa + R'-OH -> R-COOH.
Oxidative Cleavage of Alkenes: With alkaline KMnO4.

Reactions of Carboxylic Acids

Salt Formation: With Base (NaOH), Carbonates (Na2CO3), Bicarbonates (NaHCO3 - Effervescence of CO2), Metals (Na).
Reaction involving -OH group:
- Acid Halides: With PCl5 or SOCl2.
- Esters: With Alcohols (conc. H2SO4). Fruity smell.
- Amides: With Ammonia (NH3) -> Ammonium salt -> Amide (-CONH2).
- Anhydrides: Dehydration with P2O5.
Reduction:
- Partial: To Alcohols (LiAlH4).
- Complete: To Alkanes (HI/Red P).

Acetic Acid (Vinegar)

Preparation: Oxidation of Ethanol ( Fermentation of Molasses -> Ethanol -> Acetic Acid). From Acetylene. From Methyl Nitrile.

Physical Properties: Freezes at 17°C to ice-like solid (Glacial Acetic Acid). Strong vinegar odor.

Uses: Coagulant for latex, Manufacturing of plastics (PVA), rayon, medicines, solvent, vinegar (food seasoning).

Amino Acids

Contain both Amino (-NH2) and Carboxyl (-COOH) groups. Alpha-Amino Acids: Both groups on alpha-carbon (e.g., Glycine, Alanine). Building blocks of proteins.

Classification:
- Neutral: 1 NH2, 1 COOH (Glycine).
- Acidic: 1 NH2, 2 COOH (Aspartic Acid, Glutamic Acid).
- Basic: 2 NH2, 1 COOH (Lysine, Histidine).
Essential Amino Acids: Body cannot synthesize, must be in diet (10 types). Deficiency causes disease.
Non-Essential Amino Acids: Body can synthesize (10 types).

Zwitterion (Dipolar Ion)

In aqueous solution, proton transfers from -COOH to -NH2. Exists as dipolar ion (Zwitterion). Amphoteric nature (reacts with both acids and bases). Isoelectric point.

Peptides and Proteins

Peptide Bond: Amide linkage (-CO-NH-) formed by condensation of amino acids.
Polypeptides: Many amino acids linked. Molar mass < 10,000.
Proteins: Polypeptides with molar mass > 10,000. Complex structures. Hydrolysis yields amino acids.

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Chapter 13

chemistry • intermediate 12th