Crotonaldehyde 2,4-Dinitrophenylhydrazone is the 2,4-dinitrophenylhydrazone derivative of crotonaldehyde, formed by reacting crotonaldehyde with 2,4-dinitrophenylhydrazine (DNPH). It is primarily used as an analytical reference standard in chemistry for the identification and quantification of crotonaldehyde in environmental samples, food safety testing, and other matrices. This stable, colored compound allows for sensitive detection using techniques such as UV-Vis spectroscopy or HPLC, enabling trace-level analysis of crotonaldehyde, a toxic and potentially carcinogenic aldehyde. It is also utilized in research to characterize hydrazone derivatives, study carbonyl compound reactivity, and confirm functional groups in synthetic organic chemistry.