| Test | Reagent | Result | Detects | Does NOT detect |
|---|---|---|---|---|
| Tollens' | Ammoniacal AgNO3 | Silver mirror | All aldehydes | Ketones |
| Fehling's | Cu2+ tartrate/NaOH | Brick-red Cu2O | Aliphatic aldehydes, reducing sugars | Aromatic aldehydes (benzaldehyde), ketones |
| 2,4-DNP | 2,4-Dinitrophenylhydrazine | Orange/yellow ppt | ALL carbonyl (aldehyde + ketone) | Non-carbonyl compounds |
| Schiff's | Decolorized fuchsin | Pink/magenta color | Aldehydes | Ketones |
| Iodoform | I2/NaOH | Yellow CHI3 crystals | Methyl ketones (CH3CO-R), CH3CHO, ethanol | Non-methyl ketones, other aldehydes |
Key distinction for NEET: 2,4-DNP cannot distinguish aldehyde from ketone. Tollens' distinguishes aldehyde from ketone. Fehling's distinguishes aliphatic aldehyde from aromatic aldehyde.