Kinetics and mechanism of dehydrochlorination of 3-chloro-1,5-diarylformazans and their mass spectra

In aqueous dioxane containing triethylamine the title 3-chloroformazans 1 a re converted into the corresponding 1,4-bis(arylazo)-3,6-diaryl-1,2,4,5-tet razines 3 via head-to-tail dimerization of the intitially formed 1,3-dipola r ions 2. The kinetics of triethylamine-catalyzed dehydrochlorination of 1 in 70% dioxane at 27 degreesC and ionic strength of 0.1 were studied. The r ate data were linearly correlated with enhanced Hammett substituent constan ts sigma (-)(x) and an overall rho value of 0.2 was determined for the vari ation of the N-aryl substituent. These results were interpreted in terms of a two-step mechanism. Also, the mechanisms of the unimolecular fragmentati on of 1 and 3 in the mass spectrometer are discussed.