摘要
以咪唑为原料,经两次硝化、重排、硝化、中和成盐5步反应得到目标产物2,4,5-三硝基咪唑铵盐,总收率为57.7%,纯度大于96%。研究了混酸硝化、醋酐硝化和重排反应的反应机理,讨论了影响各步反应的主要因素,并对各因素进行了优化,确定最佳工艺条件。
实验表明：合成4-硝基咪唑的较优条件为：反应温度为125℃,反应时间为12 h,n(咪唑)：n(68%硝酸)：n(98%硫酸)=1：3：4,4-硝基咪唑的产率可达80.3%；合成1,4-二硝基咪唑的较优条件为：反应温度为25℃,反应时间为10 h,n(4-硝基咪唑)：n(醋酸)：n(醋酐)：n(硝酸)=1：3.5：2：2,产物收率最高可达94.1%；合成2,4-二硝基咪唑的较优条件为：1,4-二硝基咪唑3 g,氯苯30 mL,反应温度为125℃,反应时间为10 h,2,4-二硝基咪唑的收率最高可达93.3%；2,4,5-三硝基咪唑铵盐的较优合成工艺为：n(2,4-二硝基咪唑)：n(发烟硝酸)：n(20%发烟硫酸)=1：12：13.7,反应温度为95℃,反应时间为15 min,后处理反应液pH为0.5,采用乙醚作萃取剂,产物收率为81.7%。
采用红外光谱、核磁共振氢谱和质谱等对目标产物进行了结构表征；对目标产物进行差示扫描量热法DSC(分解温度为308℃)测试,结果表明目标产物具有良好的热稳定性；通过理论计算得到爆速、爆压、爆热、爆温、爆容等爆炸性能参数,分别为8782 m·s-1、34.6 GPa、1203.94 kJ·mol-1、4395.88 K、814.55 L·kg-1,爆炸性能接近RDX；机械感度测试结果表明目标化合物具有较低的撞击感度和摩擦感度,安全性能显著优于RDX,与TNT相当；综合考虑,2,4,5-三硝基咪唑铵盐可作为一种高能钝感炸药。
Ammonium 2,4,5-trinitroimidazole was prepared via five steps:twice nitration, rearrangement, nitration and neutralization, using imidazole as a starting material. The total yield is 57.7% in a purity of 96%. The reaction mechanisms of mixed acid nitration, acetic nitration and rearrangement were studied. Major factors which influenced on reaction were investigated and the optimal technological conditions of unit reaction were optimized.
The optimum synthesis conditions of 4-nitroimidazole were obtained as follows:the molar radio of imidazole to nitric acid (68%) to sulfuric acid(98%) was 1:3:4, react 12 h under 125℃, the yield of 4-nitroimidazole was 80.3%. The optimum synthesis conditions of 1,4-dinitroimidazole were obtained as follows:the molar radio of 4-nitroimidazole to acetic acid to acetic anhydride to nitric acid was 1:3.5:2:2, react 10h under 25℃, the yield of 1,4-dinitroimidazole was 94.1%. The optimum synthesis conditions of 2,4-dinitroimidazole were obtained as follows:the reaction solution contain 1 g 1,4-dinitroimidazole per 1 mL chlorobenzene, react 10 h under 25℃, the yield of 2,4-dinitroimidazole was 93.3%. The optimum synthesis conditions of ammonium 2,4,5-trinitroimidazole were obtained as follows:the molar radio of 2,4-dinitroimidazole to fuming nitric acid to fuming sulfuric acid was 1:12:13.7, react 15 min under 95℃, the pH of reaction solution after treatment was 0.5, using aether as the extracting agent, the yield of ammonium 2,4,5-trinitroimidazole was 81.7%.
The products were characterized by MS, IR,1H NMR, and the properties of ammonium 2,4,5-trinitroimidazole were studied. The thermal stability was tested by differential scanning calorimetry(DSC), the decomposition temperature was 308℃; the explosive performances including explosion velocity, detonation pressure, heat of explosion, explosion temperature and specific volume were obtained by theoretical calculation, the values are 8782 m·s-1,34.6 GPa,1203.94 kJ·mol-1,4395.88 K,814.55 L·kg-1, respectively, and were found to be comparable to those of RDX. The results of mechanical sensitivity tests showed that the safety performances of the product were close to TNT, better than RDX. To conclude, ammonium 2,4,5-trinitroimidazole could be used in the field of insensitive high energy materials.
引文
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