Electronic Excitation Energy Partitioning in Dissymmetric Dioxetane Thermolyses. The Absolute Chemiluminescence Yields and Triplet to Singlet Excited State Ratios for 3-Acetyl-4,4-dimethyl-1,2-dioxetane

Prerequisite to the logical design of efficient chemiluminescent systems is the detailed knowledge of the fundamental excitation steps in known chemiluminescent processes. The study of the unimolecular thermal decomposition of 1,2-dioxetanes, subsequent to the isolation and characterization of the first dioxetane in 1969, has provided considerable insight into the chemistry of this ring system. Primary emphasis in the study of the excitation process in 1,2-dioxetanes has been given to the determination of those factors (energetic, geometric, Franck-Condon) which control the total excited state yield and the ratio of triplet to singlet excited state products. Any postulated excitation mechanism must account for the relatively high activation energies, the efficient production of eta pi excited state carbonyl containing products, and the high triplet to singlet excited state ratios observed for nearly all alkyl or phenyl substituted 1,2-dioxetane thermal decompositions.