Temperature Dependence of the Photochemistry of Aryl Alkyl Ketones

Article abstract of DOI:10.1021/ja00345a030

The photochemistry of several phenyl alkyl and p-anisyl alkyl ketones has been examined using laser flash photolysis and conventional quantum yield techniques.The methoxy-substituted ketones show higher activation energies (ΔE_a ca. 3 kcal mol^-1) for the Norrish type I and type II processes.It is concluded that both reactions are adiabatic processes occurring from the triplet n?<*> surface.In the case of p-methoxy-substituted ketones the upper n?<*> surface is reached from the low-lying ??<*> triplet, with the energy gap between both states reflected as an increase in the activation energy.