Unknown compound
        |
        v
  [Add 2,4-DNP]
  Orange/yellow ppt?
  YES → C=O group present (aldehyde OR ketone)
  NO  → No carbonyl
        |
  [If YES: Add Tollens' reagent]
  Silver mirror?
  YES → ALDEHYDE (-CHO)
  NO  → KETONE (C=O, not -CHO)
        |
  [If Aldehyde: Add Fehling's solution]
  Brick-red Cu2O ppt?
  YES → Aliphatic aldehyde (e.g., CH3CHO)
  NO  → Aromatic aldehyde (e.g., C6H5CHO)
        |
  [If Ketone: Add I2/NaOH]
  Yellow CHI3 ppt?
  YES → METHYL KETONE (CH3CO-R)
  NO  → Non-methyl ketone
        |
[Add neutral FeCl3]
Violet/blue/green color?
YES → PHENOLIC -OH
        |
[Add NaHCO3]
CO2 effervescence?
YES → CARBOXYLIC ACID (-COOH)
        |
[Add CHCl3 + KOH, heat]
Foul smell (isocyanide)?
YES → PRIMARY AMINE (-NH2)