arylhalogenide

An aryl halide is an aromatic compound in which a halogen atom is attached directly to an sp2-hybridized carbon of an aromatic ring. Common halogens are fluorine, chlorine, bromine, and iodine.

Common examples include fluorobenzene, chlorobenzene, bromobenzene and iodobenzene. Polyhalogenated derivatives such as 1,4-dichlorobenzene are also encountered.

In contrast to alkyl halides, aryl halides typically do not undergo SN1 or SN2 substitutions at the halogen-bearing carbon, making them relatively unreactive in direct nucleophilic substitution. They readily participate in transition-metal-catalyzed cross-coupling reactions, such as Suzuki-Miyaura, Heck, Sonogashira, and Negishi couplings, enabling formation of C-C and C-heteroatom bonds.

Preparation methods include electrophilic halogenation of arenes, and the Sandmeyer reaction, which converts aryl diazonium salts to aryl halides. Aryl chlorides can also be prepared from phenols via conversion to chlorides, while fluoroarenes require more specialized fluorination approaches.

Aryl halides are versatile building blocks in organic synthesis and are widely used in pharmaceuticals, agrochemicals, and materials science. Some entries in this class can be hazardous or toxic, and handling often requires appropriate safety precautions.