Rebirth of polyene chemistry

Abstract

Polyene chemistry has attracted little attention of organic chemists due to the scarcity of known compounds and lack of novel properties. The concept of cross-conjugation was also overlooked by them. However, recently a number of new compounds and such novel properties have been discovered that attract the interest of physicists. “Cross-conjugation” has become one of the most important keywords in these areas. We have already noticed the importance of cross-conjugation and began to reconstruct the polyene chemistry from theoretical stand-point. There a cross-conjugated hydrocarbon is a non-linear acyclic and monocyclic conjugated hydrocarbon constructed by fusing two or more linear polyene networks, all having one Kekulé structure. Then radialenes, fulvenes, and quinoides are included into this category. The stability of these molecules is highly correlated with the topological index Z, and also well correlated with the mean length of conjugation L. These discussions are extended to the theoretical justification and indication of the coverage of “organic electron theory”.