THERMAL DEGRADATION STUDIES ON OXADIAZOLES.
ROYAL AIRCRAFT ESTABLISHMENT FARNBOROUGH (ENGLAND)
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2,5-DIPHENYL-1,3,4-OXADIAZOLE AND 3,5-DIPHENYL-1,2,4-OXADIAZOLE WERE PYROLYSED IN DEALED AMPOULES AND THE VOLATILE DEGRADATION PRODUCTS EXAMINED EITHER BY GAS LIQUID CHROMATOGRAPHY OR BY MASS SPECTROMETRY. Good agreement was obtained between the results of the two analytical techniques. Despite a considerable difference in the thermal stability of the two compounds, the major breakdown products, benzonitrile and phenyl isocyanate, were the same in both cases. The penyl isocyanate further reacted to a certain extent to give diphenylcarbodiimide and carbon dioxide. As the 1,3,4-oxadiazole structure was the more thermally stable, polyphenylene-1,3,4-oxadiazole was prepared and its degradation studied by the sealed ampoule method and also by flash pyrolysis into a G.L.C. using either the tungsten filament technique, or that involving introduction of a small boat containing polymer into a previously heated furnace. The results obtained for the polymer by the three methods are compared and contrasted and the mechanism of decomposition compared with that of the model compounds. Author
- Organic Chemistry
- Polymer Chemistry