69624-87-9Relevant academic research and scientific papers
Azomethineimine. VI. On the Thermic Behaviour of the Photochromic System Azomethineimine/Diaziridine, Investigated by Means of the Photoproducts of Pyrazolidone-(3)-Azomethineimines
Geissler, G.,Menz, I.,Angermueller, K.,Tomaschewski, G.
, p. 197 - 204 (2007/10/02)
The photochemically obtained cycloproducts 2 of pyrazolidone-(3)-azomethineimines 1 react thermically to 1 in aprotic solvents.This backreaction was investigated by following up the growth of the intensive long wave absorption band of 1.The kinetic analysis was carried out according to Swinbourne.The thermic backreaction is accelerated by factors favouring a polarization of the C-N(2)-bond (Cδ+ - Nδ-) of diaziridine 2.Such factors are polar solvents, donors in the substituent R and extensive, easily polarizable ?-electronic systems in R.The influence of substituents on the backreaction can be correlated by means of the ?+-Hammett-constants.For most compounds the values of EA ca. ΔH(excit.),ΔS(excit.) and ΔG(excit.) were determined.The possible reaction mechanism is discussed.The influence of steric factors on the thermic backreaction is regarded as a first indication of an exo-form of the bicyclic diaziridines 2.
