4-Iodobenzonitrile is an organic compound featuring a benzene ring substituted with an iodine atom and a nitrile (cyano) group at the para positions. It is a white to off-white crystalline solid with a molecular formula of C7H4IN. This compound is a versatile bifunctional building block in organic synthesis. Its primary application is as a key intermediate in the synthesis of more complex molecules, particularly in pharmaceutical and materials chemistry research. The iodine atom serves as an excellent site for cross-coupling reactions (e.g., Suzuki, Sonogashira, Heck reactions), while the nitrile group can be hydrolyzed to carboxylic acids, reduced to amines, or serve as a precursor to heterocycles like tetrazoles. It is frequently used in the preparation of liquid crystals, OLED materials, and various biologically active compounds. The compound should be handled with care in a well-ventilated area, using appropriate personal protective equipment. It is stable under recommended storage conditions but may decompose upon heating to produce toxic fumes, including hydrogen iodide and nitrogen oxides.