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<p>3,5-Dimethyl-4-hydroxyphenylpentazole (DHPP) has attracted considerable interest as the most promising precursor for preparing cyclopentazolate (cyclo-N<sub>5</sub><sup>−</sup>) anions reported to date. However, there is limited information available regarding its structural properties and thermal stability, which hinders the large-scale preparation of cyclo-N<sub>5</sub><sup>−</sup> anions. In this study, optical microscopy and a microgas flowmeter were employed to visualize the rate of gas release during DHPP decomposition, providing insights into its physical properties. Low-temperature ultraviolet-visible (UV–Vis) spectroscopy analysis revealed that the methanol solution of DHPP remains stable at a critical temperature of − 20&#xa0;°C. Furthermore, the crystal structures of 3,5-dimethyl-4-hydroxyphenylazide (DHPA), 2,6-dimethylbenzoquinone (DBQ), and 4-(4-hydroxy-3,5-dimethylphenyl)imino-2,6-dimethylcyclohexa-2,5-dienone (IDCD) were determined using single-crystal X-ray diffraction, further elucidating the multistep mechanism of DHPP decomposition. The stability of the pentazole ring was assessed using density functional theory (DFT), and the results suggest that the para-hydroxyl or meta-methyl groups may enhance the delocalization of the pentazole ring, thereby improving the stability of DHPP.</p>

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Experimental and theoretical investigation into the decomposition mechanism of 3,5-dimethyl-4-hydroxyphenylpentazole

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年3月14日

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  • Lei Chen,
  • Chao Gao,
  • Chong Zhang,
  • Chengguo Sun,
  • Deren Kong,
  • Bingcheng Hu

摘要

3,5-Dimethyl-4-hydroxyphenylpentazole (DHPP) has attracted considerable interest as the most promising precursor for preparing cyclopentazolate (cyclo-N5−) anions reported to date. However, there is limited information available regarding its structural properties and thermal stability, which hinders the large-scale preparation of cyclo-N5− anions. In this study, optical microscopy and a microgas flowmeter were employed to visualize the rate of gas release during DHPP decomposition, providing insights into its physical properties. Low-temperature ultraviolet-visible (UV–Vis) spectroscopy analysis revealed that the methanol solution of DHPP remains stable at a critical temperature of − 20 °C. Furthermore, the crystal structures of 3,5-dimethyl-4-hydroxyphenylazide (DHPA), 2,6-dimethylbenzoquinone (DBQ), and 4-(4-hydroxy-3,5-dimethylphenyl)imino-2,6-dimethylcyclohexa-2,5-dienone (IDCD) were determined using single-crystal X-ray diffraction, further elucidating the multistep mechanism of DHPP decomposition. The stability of the pentazole ring was assessed using density functional theory (DFT), and the results suggest that the para-hydroxyl or meta-methyl groups may enhance the delocalization of the pentazole ring, thereby improving the stability of DHPP.