Transient spectroscopy and kinetics of the reactions of mesocyclic diamines with tert-butoxyl and with ketone triplets. Effects of ring conformation

Abstract

Absolute rate constants for the reactions of tert-butoxyl and triplet benzophenone, with a series of di-tert-amines have been obtained via laser flash photolysis. These diamines have in common the feature that the nitrogen centers are in the backbone of an aliphatic eight-membered ring at positions 1 and 5. A modest rate enhancement is observed, particularly for 1 in its H-abstraction reaction with tert-butoxyl, which may be explained by the operation of a stereoelectronic effect. From the absorption maxima of the radical cations of these diamines (produced quenching acetophenone triplets), information concerning the conformations of the eight-membered rings may be inferred. It is concluded that these radical-cations are stabilized by relatively strong through-space bonding interactions between the two nitrogen centers.