1 1 orbita1 theory has had some notable successes in the ana1ysis of individua1 organic reactions and in corre1ations between reaction series. Gen ll? the theory has invoked to exp1ain known chemica1 phenomena, and rather infrequent1y broad1y-based predictions. In 1965 Woodward and published ? series of papers the 1 1 orbita1 inter pretation of various types of concerted cyc10-addition reactions, which hitherto had rather 1? understood. Because these processes (now known as pericyclic reactions) had great synthetic importance, and because the Woodward-Hoffmann theory was stated so...