Quantum Mechanics Study Of The Transition State Of Response Acceleration And High-speed Reaction Period In Thermal Decomposition Of Nitromethane

Energetic materials has a long history,energetic materials has the feature that it isexplosive,and it can release large amounts of high-speed and high output energy afterspecific excitation conditions.So it is applied to the fields of military and civilianwidely.Energetic materials can be used as launch drugs, propellants, explosives anddetonating powder. Due to the high energy output of energetic materials, it can alsobe an important part as a weapon. On the fields of civilian, energetic materials canalso be used as a civilian blasting industrial explosives, fireworks,and so on.It can beused for mining, construction, oil field, geological exploration, processing ofexplosion, fireworks, movie and television photography etc.Because of the importantapplication of energetic materials, a more accurate understanding of the nature andmechanism of pyrolysis can improve efficiency. On the other hand, due to the largepower of energetic materials and it may be more sensitive to external stimuli, thesecurity problem of energy storage, transportation and other aspects of energeticmaterials has cropped up. Therefore, the study for thermal decomposition mechanismof the energetic materials under high temperature and high-pressure has become a hotissue of the world.Nitromethane（Molecular formula:CH₃NO₂）is a typical energetic materials, itsmolecular composition is simple relatively, so it often as a prototype for energeticmaterials studied extensively. Nitromethane is explosive, it is the most simple nitrocompounds of organic chemistry,it can be researched as typical of other nitroderivatives. Therefore, the research of nitromethane has a very important theoreticaland practical significance.It has been studied from the1930s to the present, the studyof their properties and thermal decomposition mechanism has been ongoing. With thecontinuous improvement of the performance of computer hardware,the developmentof computational physics, quantum chemistry calculations and molecular modelingtechnology also has developed rapidly, the research of nitromethane has been a largenumber of valuable breakthrough. The main content of this paper is based on the thermal decomposition of thesolid phase of nitromethane with ab initio molecular dynamics simulations studied byProfessor Wei in Shanghai Jiaotong University.The paper has studied the importantreactions of response acceleration period and high-speed reaction period of the wholepyrolysis process, and use Gaussian09to optimize the structure of reactants and theresultants. Then it calculate the energy, frequency,enthalpy and the transition state ofeach process.So that we can understand the reaction path of response accelerationperiod and high-speed reaction period for the thermal decomposition of nitromethane.First,for the response acceleration period. We have researched several importantreactions of response acceleration period under the level of B3LYP/6-31G.Thetransition state of the reactions are calculated using the Gaussian09software.And ithas the only one imaginary frequency of the transition state structure,and thetransition state structure checked by the IRC.Through the analysis of transition stateto understand the low-energy response path of the response acceleration period. Aftercalculation can be seen,CH₃NO₂can become cis_CH₃ONO and trans_CH₃ONOthrough the transition state TS1and TS2.The energy barrier of these two reactions areboth higher than the C-N bond dissociation.Trans_CH₃ONO can break up into CH₂Oand HNO subsequently.Secondly,for the high-speed reaction period. All of the reactants, intermediates,products and transition state structure optimized by using the density functionalmethod B3LYP with6-31G basis set.With frequency analysis, all of the reactants,intermediates, products have no imaginary frequency, and transition state has the onlyone imaginary frequency, then show the IRC verification of all the transition statestructure. The main reactions of high-speed reaction period are the reaction of protontransfer.This stage has appeared two final product:H₂O and CO₂in the whole thermaldecomposition process, during which it also produced a number of important carrierof hydrogen molecules, such as H₂O, CNO, NCO, etc.They have played a leadingrole in the proton transfer process soon.After the analysis of the transition state,according to the calculations of the energy barrier can be seen, H₂O and HCNOproton transfer occurs through the transition state TS10generate the CNO and H₃Oreaction, the energy barrier highest for48.40kcal/mol. The lowest energy barrier is the CNO and H₂N （CH）（NH） OH proton transfer occurs to generate H₂N （CH） NOHand HCNO energy barrier is only0.805kcal/mol.