📖 Theory & Concepts ▼

Aldehyde vs Ketone

Both contain C=O (carbonyl) but aldehydes have H attached, making them stronger reducing agents.

Aldehydes (R-CHO)

Carbonyl at terminus. Easily oxidized to carboxylic acids.

Examples: HCHO, CH₃CHO, C₆H₅CHO

Ketones (R-CO-R')

Carbonyl between C atoms. Resistant to mild oxidation.

Examples: CH₃COCH₃ (acetone)

Distinguishing Tests

  • Tollens': Aldehydes give silver mirror (Ag⁺ → Ag)
  • Fehling's: Aliphatic aldehydes give Cu₂O (red ppt)
  • 2,4-DNP: Both give orange ppt (confirms C=O)
  • Iodoform: CH₃CO- or CH₃CH(OH)- give CHI₃ (yellow)

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📊 Summary

Test Aldehydes Ketones Differentiates?
Tollens' ✓ Positive ✗ Negative Yes
Fehling's ✓ Aliphatic only ✗ Negative Yes
2,4-DNP ✓ Positive ✓ Positive No (both +ve)
Iodoform CH₃CHO only CH₃CO- only Specific groups

Observations

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