ABSTRACT
Numerous reviews on the photochemistry and photophysics of ketones and azoalkanes are already available. This chapter focuses on intermolecular photoreactions of azoalkanes, which are compared with known data for ketones. It focuses on some new developments, which have largely resulted from investigations on the comparative photochemistry of bicyclic azoalkanes with simple ketones. The prototypal structures, all of which possess an n,p* configuration in both the lowest singlet- and triplet-excited states. Instructive is also a comparison of the state energy diagrams of ketones and azoalkanes. The change in dipole moment upon excitation provides another contrast between ketones and azoalkanes. For ketones, electronic excitation involves the promotion of a lone pair electron from oxygen to the carbonyl carbon, which may be part of a delocalized p system in the case of aromatic ketones. The peculiar reactivity pattern of azoalkanes signifies a higher nucleophilicity of excited azoalkanes compared to ketones.
