This lesson explores the major families of oxygen-containing organic compounds, their structures, functional groups, reactions, and distinguishing tests.

1. Core Concepts (Short Notes)

13.1 Alcohols (R–OH)

• Contain the hydroxyl (–OH) group.

• Classified as primary (1°), secondary (2°), or tertiary (3°).

Properties:

• Hydrogen bonding → high boiling points.

• Soluble in water (lower alcohols).

Reactions:

• Oxidation:

  • 1° → aldehydes → carboxylic acids.

  • 2° → ketones.

  • 3° → no oxidation.

13.2 Phenols (Ar–OH)

• –OH group attached to a benzene ring.

• More acidic than alcohols.

Reactions:

• React with Na → hydrogen gas.

• Undergo electrophilic substitution (e.g., bromination) easily.

13.3 Aldehydes (R–CHO)

• Contain the carbonyl group at the end of a chain.

Properties:

• Easily oxidized → carboxylic acids.

Tests:

• Tollens’ test → silver mirror.

• Fehling’s/Benedict’s test → brick-red precipitate.

13.4 Ketones (R–CO–R')

• Carbonyl group in the middle of chain.

• Cannot be oxidized further.

Reactions:

• React with 2,4-DNP → orange precipitate.

• Do NOT give Tollens’ or Fehling’s test.

13.5 Carboxylic Acids (R–COOH)

• Contain both carbonyl and hydroxyl groups.

• Strong hydrogen bonding.

Properties:

• Acidic (react with bases and carbonates).

Reactions:

• Neutralization → salts.

• Esterification with alcohols (acid catalyst).

• Reduction → alcohols.

13.6 Esters (R–COOR')

• Formed from acid + alcohol.

• Fruity smell.

Reaction: Carboxylic acid + alcohol ⇌ ester + water

2. Key Reactions & Equations to Memorize

Oxidation Reactions

• Ethanol → ethanal → ethanoic acid.

• Propan-2-ol → propanone.

Esterification

R–COOH + R'–OH ⇌ R–COOR' + H₂O

Phenol Reaction With Bromine Water

Phenol + Br₂ → 2,4,6-tribromophenol (white precipitate)

Tests

• Tollens’ → aldehydes.

• 2,4-DNP → aldehydes & ketones.

• Sodium carbonate → acids produce CO₂.

3. Tips & Tricks for Exams

• Identify carbonyl compounds by their smell and tests.

• Remember: aldehydes oxidize, ketones do not.

• Phenol undergoes substitution more easily than benzene.

• Carboxylic acids dissolve in alkalis → salt formation.

• For naming esters: alcohol part → “yl”, acid part → “oate”.

• Use oxidation color changes (e.g., dichromate orange → green).

4. Important Points to Remember

• Functional groups dictate chemical behavior.

• Alcohol oxidation level depends on classification.

• Phenols are more acidic due to resonance stabilization.

• Esters have pleasant smells and form through esterification.

Aldehydes and ketones both contain carbonyl groups, but differ in placement and reactivity.