The Sandmeyer reaction is a chemical process used to synthesize aryl halides from aryl amines. In this reaction, an aryl amine is first converted into a diazonium salt, typically using nitrous acid. The diazonium salt can then be treated with a copper(I) halide, such as copper(I) bromide, to replace the diazonium group with a halogen atom, resulting in the formation of the desired aryl halide. This reaction is particularly useful in organic chemistry for creating compounds that are important in pharmaceuticals and dyes. The Sandmeyer reaction allows for the selective introduction of halogens, which can further participate in various chemical reactions, expanding the versatility of aryl halides in synthetic applications.