Devi Rimpi, Sharma Kalpana, Ghule Vikas D
Department of Chemistry, National Institute of Technology Kurukshetra, Kurukshetra 136119, Haryana, India.
ACS Omega. 2025 May 21;10(21):21985-21993. doi: 10.1021/acsomega.5c02042. eCollection 2025 Jun 3.
Dinitromethyl and trinitromethyl moieties are promising functional groups in the development of energetic compounds with enhanced oxygen balance, density, and performance. The reliable data of energy content are crucial thermodynamic parameters in determining their performance and application prospects toward energetic materials (EMs). Direct experimental measurements of enthalpy of formation through bomb calorimetry are complicated due to their unstable nature and higher heat release, while the large size of these molecules limits the use of highly accurate quantum chemical methods that suffer from scaling problems. The isodesmic reaction method is commonly applied to determine the heat of formation of large EMs by cleaving them into simple molecules with known accurate experimental heats of formation and conserving the number and type of bonds on both sides of the reaction. However, the unavailability of experimental heats of formation for dinitromethane, 1,1-dinitroethane, trinitromethane, and 1,1,1-trinitroethane raises the use of nitromethane in isodesmic reactions, leads to a significant change in bond environments, and involves multiple compounds in isodesmic reactions. In this work, we calculated the gas-phase enthalpies of formation for dinitromethane, 1,1-dinitroethane, trinitromethane, and 1,1,1-trinitroethane compounds using an isodesmic reaction scheme and validated the results with quantum composite (Gaussian-4 and CBS-QB3) methods. The heats of formation obtained from the Gaussian-4 (G4) method are used to predict the energy content of EMs with dinitromethyl and trinitromethyl functional groups to reduce the error associated with different bonding environments in isodesmic reactions. We believe that the combined use of isodesmic reaction and the composite method can significantly reduce the error in the prediction of heats of formation of target dinitromethyl- and trinitromethyl-substituted EMs.
二硝基甲基和三硝基甲基部分是开发具有增强氧平衡、密度和性能的含能化合物中很有前景的官能团。能量含量的可靠数据是决定它们在含能材料（EMs）方面性能和应用前景的关键热力学参数。通过弹式量热法直接实验测量生成焓很复杂，因为它们性质不稳定且放热较高，而这些分子的大尺寸限制了因存在缩放问题而难以使用的高精度量子化学方法。等键反应法通常用于通过将大分子含能材料裂解为具有已知准确实验生成热的简单分子，并保持反应两边键的数量和类型来确定其生成热。然而，二硝基甲烷、1,1 - 二硝基乙烷、三硝基甲烷和1,1,1 - 三硝基乙烷的实验生成热无法获取，这使得在等键反应中使用硝基甲烷，导致键环境发生显著变化，并且在等键反应中涉及多种化合物。在这项工作中，我们使用等键反应方案计算了二硝基甲烷、1,1 - 二硝基乙烷、三硝基甲烷和1,1,1 - 三硝基乙烷化合物的气相生成焓，并用量子组合（高斯 - 4和CBS - QB3）方法验证了结果。从高斯 - 4（G4）方法获得的生成热用于预测具有二硝基甲基和三硝基甲基官能团的含能材料的能量含量，以减少与等键反应中不同键环境相关的误差。我们认为等键反应和组合方法的联合使用可以显著降低目标二硝基甲基和三硝基甲基取代的含能材料生成热预测中的误差。
