2,4-Dinitrochlorobenzene
2,4-Dinitrochlorobenzene (DNCB) is an organic compound with the chemical formula (ON)CHCl. It is a yellow solid that is soluble in organic solvents. It is an important intermediate for the industrial production of other compounds. DNCB is produced commercially by the nitration of "p"-nitrochlorobenzene with a mixture of nitric and sulfuric acids. Other methods afford the compound less efficiently include the chlorination of dinitrobenzene, nitration of o-nitrochlorobenzene and the dinitration of chlorobenzene. Uses. By virtue of the two nitro groups, the chloride is susceptible to nucleophilic substitution. In this way, the compound is a precursor to many  other compounds. Base gives the dinitrophenol, ammonia the dinitroaniline, methoxide the dinitroanisole, and amines the secondary amines. Laboratory use. DNCB is used as a substrate in GST enzyme activity assays. The molecule is conjugated to a single molecule of reduced glutathione which then absorbs at 340 nm. Affinity of CDNB for each class of GST varies and so it is not a good measure of activity for some forms (e.g. GSTT and GSTZ). Medical use. DNCB can be used to treat warts with an effective cure rate of 80%. DNCB induces an allergic immune response toward the wart-causing virus . Safety. DNCB induces a type IV hypersensitivity reaction in almost all people exposed to it, so it is used medically to assess the T cell activity in patients. This is a useful diagnostic test for immunocompromised patients. It can also be used to treat warts. DNCB can cause contact dermatitis.