picric acid pĭk´rĭk [key] or 2,4,6-trinitrophenoltrī˝nī˝trōfē´nōl [key], C6H2(NO2)3OH, a toxic yellow crystalline solid that melts at 122°C and is soluble in most organic solvents. Picric acid is a derivative of phenol. It reacts with metals to form metal picrates, which like picric acid itself are highly sensitive explosives that can be detonated by heat, flame, shock, or friction. The high explosives lyddite and melinite are composed mostly of compressed or fused picric acid. Picric acid is often used as a booster to detonate another, less sensitive explosive, such as TNT (trinitrotoluene). Although picric acid can be synthesized by nitration of phenol, higher yields are obtained if chlorobenzene is used as a starting material; the latter method involves several steps and the formation of several intermediate products. In addition to its use in explosives, picric acid has been used as a yellow dye, as an antiseptic, and in the synthesis of chloropicrin, or nitrotrichloromethane, CCl3NO2, a powerful insecticide.
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