REACTION OF OXYGEN WITH GAMMA,DELTA-ETHYLENIC PHENYLHYDRAZONES - MODEL REACTION OF END-GROUP BEHAVIOR IN PHENYLHYDRAZINE-ACCELERATED OXIDATION OF NATURAL-RUBBER

An accurate definition of terminal groups of chains in the liquid poly mers obtained by the phenylhydrazine-accelerated oxidation of natural rubber is needed. The object of the work was to use model molecules to explore the behavior of gamma,delta-ethylenic methylketone phenylhydr ozone end-groups in oxidation conditions. We have investigated the syn thesis and characterization of models of these hypothetical end-groups , methylketones and phenones 1, their phenylhydrazones 2, the alpha-(p henyldiazenyl)hydroperoxides 3 resulting from reaction of 2 with oxyge n, and the alpha-(phenyldiazenyl) alcohols 4 as characteristic derivat ives of 3 or as models of possible reduced structures in oxidized liqu id natural rubber. Three original syntheses of gamma,delta-ethylenic k etones were carried out. In the case of gamma,delta-ethylenic phenylhy drazones, the oxidation led to the expected alpha-(phenyldiazenyl)hydr operoxides and to epoxide derivatives of alpha-(phenyldiazenyl)alcohol s 5 and ketones 6. An intramolecular mechanism is proposed. The result s are used to predict the possibilities of identification of the corre sponding end-groups in liquid rubbers produced in this way.