Thermal decomposition of 4H-1,3,5-Oxadiazine derivatives

Derivatives of 1,3,5-oxadiazines are of great interest in medicine and agriculture. The thermal decomposition of 6-(4-chlorophenyl)-N-aryl-4-(trichloromethyl)-4H-1,3,5-oxadiazin-2-amines with the use of the gas chromatography/mass spectrometry (GC/MS) was studied in this work. Samples for the analysis were injected into the injector in the form of a saturated solution in acetonitrile. Thermal decomposition was carried out directly in the injector at a temperature of 300 °C in a helium flow. According to the results of GC/MS analysis, none of these 4H-1,3,5-oxadiazine derivatives could produce a peak with an appropriate molecular weight, which is connected with the thermal instability of these compounds. It was shown that during the thermal decomposition of the compounds under study, the splitting of the oxadiazine ring occurs in two main directions (A and B). In the first case, the 4-chlorobenzonitrile is cleaved, followed by splitting of the resulting 1-aryl-3-(2,2,2-trichloroethylidene)urea. In the second case, N-arylcyanamides are cleaved to form 4-chloro-N-(2,2,2-trichloroethylidene)benzamide. [Display omitted]