CHANGES OF STRUCTURE AND ENERGY ON THE ROUTE FROM DIOXETANE TO CARBONYL PRODUCTS - A QUANTUM-CHEMICAL STUDY

Energy diagrams, changes of geometry and bond orders were calculated s emi-empirically for the thermolysis of 1,5-dioxetane. Stretching of th e O-O bond, then of the C-C bond and distortion of the whole quadrangu lar structure make major, but different, contributions to the reaction coordinate on the path to formaldehyde. The activation barrier repres ents a vast region where the gaps between the ground and excited state s are small, and this favours horizontal radiationless transitions lea ding to the excitation of a product. The results show that semi-empiri cal calculations may help to provide better insight into the nature an d mechanism of the chemiluminescence excitation. (C) 1998 John Wiley & Sons, Ltd.