The photoabstraction and phosphorescence of triplet acetophenones requires a mixing between zero-order n,T* and T,R* states with interaction energies 2100 cm-I. The extent of mixing ( b z ) and the energy separation ( A E ) of the resultant states are fundamental properties of the molecule and are independent of the phenomena being observed. However, the best expressions for the radiative rate constants (eq 1) and for the reaction rate constants (eq 6 ) differ since no activation energies are involved in the former while there ?re substantial barriers to reaction in the latter. Variations in photoreactivity between compounds are then mainly manifested as activation energy differences and the reactivity of a given compound changes significantly with temperature. On the other hand the radiative rate constants show essentially no temperature dependence although they do differ widely from compound to compound. 4
ResultsPreparation of 3 and 4. The requisite 1,5-dienes, 3 and 4, were prepared as outlined in Schemes I and 11. Dieckmann cyclization of diethyl @-vinyl adipate (5)4 produced a mixture of @-keto esters which upon hydrolysis and decarboxylation Scheme I CH,Ph,PCH,Br, NaH, Me,SO 1 CHz 3