Arylidenepyridylhydrazines: Synthesis, and kinetics and mechanism of their gas-phase pyrolysis

Five arylidenepyridin-2-ylhydrazines (1a-e) were synthesized using conventional and microwave enhanced techniques, and then subjected to flash vacuum and static (sealed-tube) pyrolysis. The pyrolysates from both reactions were analyzed, and their constituents characterized and identified. Further, the kinetics of pyrolysis of the substrates were investigated over the temperature range: 497-632 K. Rates of reaction and entropies of activation at 500 K were evaluated and used to correlate substrate molecular reactivities, and to provide evidence in support of the mechanism suggested for the pyrolysis reactions. An interesting gas-phase oxidative cyclization reaction observed for the present hydrazines is described and explained. (C) 2017 Elsevier B.V. All rights reserved.