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2,4-DNP Test
2,4-Dinitrophenylhydrazine gives yellow/orange precipitate with carbonyl compounds (aldehydes & ketones).
How It Works
1
Three Unknown Compounds
Tubes A, B, C contain aldehyde, ketone, and alcohol.
2
Add 2,4-DNP Reagent
2,4-DNPH reacts with C=O group to form hydrazones (yellow/orange ppt).
3
Observe Precipitate
Yellow ppt = Aldehyde. Orange ppt = Ketone. No ppt = Alcohol.
Reaction Key
Aldehyde:
Yellow precipitate (2,4-DNP hydrazone)
Ketone:
Orange precipitate (2,4-DNP hydrazone)
Alcohol:
No precipitate (no C=O group)