ISSN:
0021-8383
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Azomethineimine. VI. On the Thermic Behaviour of the Photochromic System Azomethineimine/Diaziridine, Investigated by Means of the Photoproducts of Pyrazolidone-(3)-AzomethineiminesThe 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 absorptionband of 1. The kinetic analysis was carried out according to SWINBOURNE [5, 6]. 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 π-electronic systems in R. The influence of substituents on the backreaction can be correlated by means of the σ+-Hammett-constants. For most compounds the values of EA ≈ ΔH≠, Δ≠ and ΔG≠ 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.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/prac.19833250204
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