Green Reductive Homocoupling of Bromobenzene

Although transition-metal-catalyzed reactions are important in contemporary organic chemistry, relatively few resources for the second-year organic chemistry curriculum discuss the subject. The inquiry-based experiment described here, an iron-catalyzed preparation of biphenyl from bromobenzene, introduces this topic. The reaction uses an inexpensive and relatively benign iron precatalyst that is air- and moisture-stable, and the experiment can be performed using the equipment found in a typical organic teaching laboratory. The crude product can be analyzed by melting point determination or by gas chromatography. The experiment allows for a general discussion of redox cycles common in many metal-catalyzed reactions, redox processes of organic substrates, and green chemistry. The experiment can be used in organic or inorganic laboratories.