A special issue of the Journal of Organic Chemistry has been dedicated to the 50th anniversary of the discovery of the role of orbital symmetry in the control of organic cycloaddition reactions. The principles underlying the conservation of orbital symmetry and the consequences for understanding the mechanisms of such reactions have been formalized in the famous Woodward-Hoffmann rules, familiar to any undergraduate organic chemistry student. Over the past 50 years, the powerful ideas expressed in the Woodward-Hoffmann rules have been used to understand the mechanisms of many different types of reactions, as well as serving as a predictive tool to chart new synthetic strategies for complex molecules.
Current EFree University Partner Roald Hoffmann (Cornell) offers his perspective on the development of this fundamental advance in organic chemistry in the Preface to this special issue: http://pubs.acs.org/doi/ipdf/10.1021/acs.joc.5b01741
The Editorial accompanying the special issue may be found here: http://pubs.acs.org/doi/ipdf/10.1021/acs.joc.5b02469