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Science and Technology of Energetic Materials

Vol.70, No.1 (2009)

Research paper

Synthesis and thermal behavior of 2‚4-diaryl-3H -1‚2‚4-triazole-3-ones
Satoru Yoshino, Shogo Ihara, Masahiro Tajima, Katsuji Matsunaga,
and Atsumi Miyake
p.16-22

Abstract

1‚2‚4-Triazole-3-one derivatives with 2‚4-aryl groups (ArTOs) were synthesized and their thermal behavior was investigated using thermogravimetry / differential thermal analysis (TG / DTA), sealed cell differential scanning calorimetry (SC-DSC), and flash pyrolysis FT-IR. In addition, semiempirical molecular orbital (MO) calculations were carried out using the AM 1 method to estimate the strength of bonds and two-center energies in the ArTOs. The ArTOs were obtained in good yields by the heating of semicarbazidomethylenemalonic acid derivatives. The TG / DTA and SC-DSC results showed that the introduction of electron-releasing substituents on the 2‚4-aryl groups of ArTOs influenced their thermal characteristics. No residue was observed after TG / DTA was performed on the ArTOs. Since decomposition of ArTOs showed endothermic peaks without residue under open pan conditions, but exothermic peaks with residue under closed pan conditions, it was considered that the decomposition of ArTOs proceeds in the gas phase. Flash pyrolysis FT- IR measurements indicated the formation of isocyanate and hydrogen cyanate. This suggested that thermal decomposition of 2‚4-diphenyl-3H -1‚2‚4-triazole-3-one was mainly initiated at either the N2-C3 and N4-C5 bonds, or the N1 -N 2 and C3-N4 bonds. The calculated two-center energies of the N1-N2 and N2-C3 bonds, which correspond to the bond energies, were lower than those of the other bonds. This result supports, and is consistent with, our experimental results.

Keywords

2‚4-diaryl-3H -1‚2‚4-triazole-3-one, Semicarbazidomethylenemalonic acid,
Pyrolysis mechanism, Flash pyrolysis FT-IR, Molecular orbital calculations.

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