The Theoretical Studies On Nitrolysis Mechanism Of Preparing RDX From Urotropine

With the development of modern technology and improvement of national defence technology level, the studies on preparing of energetic materials are focused on more and more. Amount the nitryl-kind detonators, RDX possesses excellent capability. Its processing technology is practiced, but the few theoretical studies are reported. Due to the lack of theoretical investigation, the producing of RDX is limited. This must be influence on constructing of economy and national defence.The nitration mechanism of arene has important apocalypse on the nitrolysis mechanism of urotropine, so the experimental and theoretic investigations on the nitration mechanism of arene were summarized firstly in this study. Theoretical methods, ab initio and density functional theory (DFT), mainly used in this study on nitrolysis mechanism of urotropine were introduced in the second chapter.The tautomerism reaction between NO₂⁺·H₂O and H₂NO₃⁺ was calculated by B3LYP and MP2 methods at the 6-311++G^** level. In the reaction of NO₂⁺ and H₂O,the change of each thermodynamic quantity and equilibrium constant were studied using statistical thermodynamics method.Δ,H,Ea,Δ_?G and K^θat different temperature were obtained. The results indicate that the isomer,where both the two hydrogen atoms lie to the oxygen atom without the hydrogen, is the most stable one in nitration process. The Ea is 22.52 and 25.37 kJ·mol^-1 for two major channels, respectively.The geometric configuration of the monomers and complexes between urotropine and nitric acid, HA·HNO₃ and HA·2HNO₃,were optimized and the corresponding vibration frequencies were calculated by B3LYP method at 6-311++G^** and aug-cc-pVTZ level in chapter 4. Natural Bond Orbital (NBO) analysis and the calculation on temperature effect were carried out using B3LYP/6-311++G^** level. The results indicate that, in the solvent of nitric acid, the major form of urotropine is not complex formed by weak bond but the HA·HNO₃ accompanied by the ionic bond between the hydrogen and nitrogen atoms, and the most stable is the geometric configuration in which the distance of hydrogen bond is 2.745 A, bond length of O23-H9 is 2. 784 (?),bond angle of O26-C13-N7 and O26-C6-N7 is 91.1°and 101.8°,respectively. For HA·HNO₃,the bond length of C-N which is adjacent with N-H bonds is longer than the others. This indicates that the reaction of preparing RDX happens between the carbon and nitrogen atoms of C-N bond. While for HA·2HNO₃,only one chemical bond between nitrogen of urotropine and the hydrogen of nitric acid is observed, and the other is the hydrogen bond that formed by nitrogen of urotropine and the other hydrogen of nitric acid. This indicates that the break of bond is happened by stages. Structure analysis indicates that the forming of complex plays a great role in the first step of nitrolysis mechanism,every transition states in path of nitrolysis mechanism reaction were simulated by B3LYP/6-311++G(d,p) method. Zero point energy, total energy,Δ_?H andΔ_?G were obtained. The results indicate that the channelis easier than channel.