THEORETICAL CHARACTERIZATION OF THE THERMODYNAMICS OF THE PHOTOISOMERIZATIONS OF ETHYLENE AND PROPYLENE

A number of structures which may play a role in the thermal and triple t photochemistry of ethylene and propylene are calculated using ab ini tio methods. The energies and other properties obtained from these ab initio calculations are employed to calculate the heats of formation o f the structures using the bond additivity correction (BAG) method of Carl Melius. Generally, the heats of formation appear to be accurate t o within several kilocalories per mole, even for the triplet states an d transition states encountered in this study. A final analysis reache s the conclusion that the triplet-sensitized photochemistries of ethyl ene and propylene occur through the hot ground states of these materia ls rather than through their respective triplet states.