| Abstract: | Energy diagrams, changes of geometry and bond orders were calculated semi-empirically for the thermolysis of 1,2-dioxetane. Stretching of the O–O bond, then of the C–C bond and distortion of the whole quadrangular structure make major, but different, contributions to the reaction coordinate on the path to formaldehyde. The activation barrier represents a vast region where the gaps between the ground and excited states are small, and this favours horizontal radiationless transitions leading to the excitation of a product. The results show that semi-empirical calculations may help to provide better insight into the nature and mechanism of the chemiluminescence excitation. © 1998 John Wiley & Sons, Ltd. |
