Describe the reaction conditions and products formed when diazonium fluoroborate is heated with aqueous sodium nitrite in the presence of copper.

When diazonium fluoroborate is heated with aqueous sodium nitrite (NaNO₂) in the presence of copper, the Sandmeyer reaction occurs. The reaction conditions involve heating the mixture under acidic conditions. The diazo group (-N₂⁺) is replaced by a nitro group (-NO₂) on the aromatic ring, leading to the formation of a nitro compound. For instance, treating benzenediazonium fluoroborate with sodium nitrite and copper results in the production of nitrobenzene. This transformation is valuable in organic synthesis for the preparation of nitroaromatic compounds, which have various applications in the synthesis of dyes, pharmaceuticals, and agrochemicals.