This study systematically investigated the nitration reaction of 2,4-dichlorobenzotrifluoride (2,4-DCBTF),focusing on the reaction conditions,mechanism,and thermal safety.Screening experiments identified the optimal reaction conditions:n(2,4-DCBTF)∶n(HNO3)=1∶1.1,n(HNO3)∶n(H2SO4)=1∶6.5,reaction temperature of 60℃,stirring rate of 300 r/min,and reaction time of 3 h.Under these conditions,the conversion of 2,4-DCBTF reached 90%,with a selectivity for 2,4-dichloro-5-nitrobenzotrifluoride (2,4-DC 5-NBTF) of up to 91%.Density functional theory (DFT) calculations revealed that the reaction proceeds via an $HS{\mathrm{O}}_{4}^{-}$-induced nitration mechanism,where the attack of $N{\mathrm{O}}_{2}^{+}$ on the benzene ring carbon and hydrogen abstraction by $HS{\mathrm{O}}_{4}^{-}$ occur synergistically.The pathway leading to 2,4-DC 5-NBTF has the lowest energy barrier,consistent with the experimental findings.The measured reaction enthalpy was approximately -117.72 to -121.11 kJ/mol.When the stirring rate exceeded 280 r/min,mass transfer effects were eliminated,and both the maximum accumulation degree and maximum temperature of the synthesis reaction (MTSR) significantly decreased compared to lower stirring rates.A suitable feeding time of 1 h was determined,which further enhanced reaction efficiency and substantially reduced the maximum accumulation degree and MTSR compared to shorter feeding times,indicating high reaction efficiency and low thermal risk.
为了研究2,4-DCBTF硝化反应的热力学数据,及搅拌速率和加料时间对硝化反应放热行为的影响,设计了7组量热实验,见表2。在0℃下,将 1 144 g 98% H2SO4缓慢加入170.58 g 65% HNO3中配制混酸。将配制好的混酸加入反应量热仪RC1e反应釜中,开启搅拌,控制反应温度60℃,使用加料泵将351 g 2,4-DCBTF匀速加入釜中,加料结束后持续监测反应至放热完全。后处理与反应条件筛选实验一致。量热实验反应条件见表2。
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