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

- FVP and static pyrolysis of Arylidenepyridylhydrazines 1a-e.
- An interesting gas-phase oxidative cyclization reaction observed for the present hydrazines is described and explained.
- These triazoloheterocycles are noted for their antifungal, antibacterial, and herbicidal effects.

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.

71The two pyrolysis pathways are compatible with product analysis, and rates and entropy of activation.