Used primarily as a reagent to detect and characterize aldehydes and ketones in organic analysis. It reacts with carbonyl groups to form yellow, orange, or red crystalline solids known as 2,4-dinitrophenylhydrazones, which are easy to isolate and have sharp melting points, aiding in identification. Commonly used in qualitative testing in laboratories and in teaching environments to demonstrate carbonyl reactivity. Also applied in analytical chemistry for the purification and derivatization of carbonyl compounds prior to spectroscopic analysis.