Bridged compounds

A bridged compound is a chemical compound, generally an organic compound, but also possibly inorganic, that has two or more rings (a ring system) that contains a bridge—a single atom or an unbranched chain of atoms (or even just a valence bond) that connect two "bridgehead" atoms. The bridgehead atoms are defined as any atom that is not a hydrogen, and that is part of the skeletal framework of the molecule that is bonded to three or more other skeletal atoms. Clayden simplifies this description, saying that bridged bicyclic compounds "are just what the name implies—[molecules in which] a bridge of [an atom or of atoms] is thrown across from one side of the ring to the other," examples of which are shown at left and right, and below. The presence of the bridge connecting the bridgehead atoms, which are most often two non-adjacent atoms, distinguishes bridged compounds from fused ring compounds that have two rings linked by two adjacent atoms, and from spiro compounds that have two rings linked by a single atom.