Abstract Differential scanning calorimetry at an elevated external pressure (Pressure DSC) allows for shifting the vaporization of a sample to higher temperatures, thus often facilitating the direct observation of its thermal decomposition. In the present work, the thermolysis of a promising energetic material 3,5-dinitropyrazole was studied under pressures up to 10 MPa. The thermokinetic analysis of the datasets acquired at 2 and 5 MPa exhibited a pronounced kinetic compensation, thus allowing to build the joint formal kinetic model. The final kinetic scheme is comprised of the two parallel reactions, viz., the first-order process (Ea = 198 kJ mol-1) along with a first-order autocatalysis (Ea = 127 kJ mol-1). The experiment was complemented with the highly accurate CCSD(T)-F12 quantum chemical calculations. Theory revealed an unusual primary decomposition channel, viz., a sigmatropic [ 1 , 5 ]H-shift followed by the pyrazole ring opening yielding a molecular nitrogen and a nitro radical as simple primary products. Apart from this, the comparative thermogravimetry at a normal pressure yielded the vapor pressure of 3,5-dinitropyrazole along with the internally consistent set of phase change enthalpies. In general, the pressure DSC is a facile technique to study the true decomposition kinetics of the compounds that vaporize/sublime in conventional DSC experiments.

中文翻译：

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用于高能材料的压力 DSC。第 2 部分。 3,5-二硝基吡唑的蒸发和热分解之间的切换

摘要 外部压力升高的差示扫描量热法（压力 DSC）允许将样品的汽化转移到更高的温度，因此通常有助于直接观察其热分解。在目前的工作中，在高达 10 MPa 的压力下研究了有前途的含能材料 3,5-二硝基吡唑的热分解。在 2 和 5 MPa 下获得的数据集的热动力学分析表现出明显的动力学补偿，从而允许建立联合正式动力学模型。最终的动力学方案由两个平行反应组成，即一级过程 (Ea = 198 kJ mol-1) 以及一级自催化 (Ea = 127 kJ mol-1)。该实验辅以高精度的 CCSD(T)-F12 量子化学计算。理论揭示了一个不寻常的初级分解通道，即 sigmatropic [ 1 , 5 ] H 位移，然后是吡唑开环，产生分子氮和硝基自由基作为简单的初级产物。除此之外，在常压下的比较热重分析产生了 3,5-二硝基吡唑的蒸气压以及内部一致的相变焓集。一般而言，压力 DSC 是研究在常规 DSC 实验中蒸发/升华的化合物的真实分解动力学的简便技术。5-二硝基吡唑以及一组内部一致的相变焓。一般而言，压力 DSC 是研究在常规 DSC 实验中蒸发/升华的化合物的真实分解动力学的简便技术。5-二硝基吡唑以及一组内部一致的相变焓。一般而言，压力 DSC 是研究在常规 DSC 实验中蒸发/升华的化合物的真实分解动力学的简便技术。