pdimethylaminobenzaldehyde

p-Dimethylaminobenzaldehyde, also known as Ehrlich's reagent, is an organic compound with the chemical formula (CH₃)₂NC₆H₄CHO. It is a substituted benzaldehyde where a dimethylamino group is attached to the para position of the benzene ring. This compound typically appears as a white to pale yellow crystalline solid.

Ehrlich's reagent is widely recognized for its use as a diagnostic test, most notably for the detection of indole. In the presence of an acid, p-dimethylaminobenzaldehyde reacts with indoles to form a colored complex, usually pink or purple. This reaction is the basis of the Ehrlich test, which can be used in various fields, including microbiology to identify bacteria that produce indole, and in forensic science to detect certain illicit substances derived from indole. It is also employed in analytical chemistry for the quantitative determination of specific compounds. The reagent is typically prepared by dissolving p-dimethylaminobenzaldehyde in a suitable solvent, such as ethanol or hydrochloric acid.