The Gattermann reaction serves as a historical and functional alternative to the Sandmeyer reaction — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

While the Sandmeyer reaction employs a homogeneous or highly soluble $Cu(I)$ halide salt, the Gattermann reaction utilizes elemental copper powder ($Cu^0$) suspended in the corresponding hydrogen halide acid (e.g., $HCl$ or $HBr$). Because the metallic copper powder acts as a heterogeneous solid-state catalyst, the reaction is reliant on surface area and electron transfer from the solid metal to the solution, which is generally less efficient. Consequently, the Gattermann reaction typically affords a noticeably lower yield of the aryl halide compared to the Sandmeyer process.