| Hexanitrohexaazaisowurtzitane,also named as CL-20,is one of the most comprehensive single explosives at present,which has excellent application prospect.However,“three-step”synthesis process of CL-20 starting from benzylamine makes its cost high,which seriously limits its large-scale application.Therefore,the development of efficient synthesis process to achieve CL-20 high-efficiency,green and low-cost manufacturing has important application value and practical significance for expanding the application scenario of CL-20 and realizing the renewal and replacement of weapon systems.In this study,the effect mechanism of electronic structures of primary amine?benzyl amine,benzoyl amine and benzenesulfonyl amine?on the construction of caged skeleton was elaborated.Then,a predicted model of describing the condensation reaction barrier based on nitrogen atom form amino group in primary was established.Based on the prediction and experiment,sulfamates?ammonium salt,potassium salt and sodium salt?are considered to be an alternative of benzylamine to synthesize CL-20.Finally,the feasibility of synthesis of CL-20 in two steps via condensation and nitrification by sulfamate was confirmed experimentally,and the optimum parameters for synthesis of CL-20 were obtained.Main research contents and results are as follows:?1?The electronic structures of benzyl amines were calculated.The results show that the Hirshfeld charge of amino N atom of benzyl amine is-0.230--0.210 au;the N-H bond length is 1.0170-1.0195?,and N-H bond energy is 105.5-108.5 kcal·mol-1.The distance of N atom to H+in complex is 2.10-2.20?,and the attraction potential of that is 1.75-1.95 kcal·mol-1,and the reaction energy barrier is between 13.0-17.0 kcal·mol-1?The synergistic effect of what the H atom on amino group is easy to leave and the amino group has a strong attraction to the positive center makes caged skeleton condensation reaction barrier low,which is the reason why benzyl amines are easy to construct caged skeleton with glyoxal.?2?The electronic structures of benzoyl amines were calculated.The results show that the Hirshfeld charge of amino N atom of benzoyl amine is-0.165--0.145 au;the N-H bond length is 1.0075-1.0090?,and N-H bond energy is 127.5-131.0 kcal·mol-1.The distance of N atom to H+in complex is 2.50-2.80?,and the attraction potential of that is 0.15-0.75 kcal·mol-1,and the reaction energy barrier is between 26.5-30.5 kcal·mol-1?The synergistic effect of what the H atom on amino group is hard to leave and the amino group has a weak attraction to the positive center makes caged skeleton condensation reaction barrier high,which is the reason why benzoyl amines are hard to construct caged skeleton with glyoxal.?3?The electronic structures of benzenesulfonyl amines were calculated.The results show that the Hirshfeld charge of amino N atom of benzenesulfonyl amine is-0.200--0.180 au;the N-H bond length is 1.0135-1.0205?,and N-H bond energy is 115.5-119.5 kcal·mol-1.The distance of N atom to H+in complex is 2.75-2.95?,and the attraction potential of that is 0.01-0.22 kcal·mol-1,and the reaction energy barrier is between 22.0-28.0 kcal·mol-1?With the energy barrier of the condensation between benzenesulfonyl amine and glyoxal is between that of which by benzyl amine and that of which by benzoyl amine,it is predicted that benzylsulfonylamide derivatives can condense with glyoxal to form caged skeleton,in which,sulfamate?ammonium salt,potassium salt and sodium salt?are considered to be an alternative to synthesize CL-20.?4?The synthesis of caged skeleton by the reaction of sulfamate with glyoxal was studied.The results show that,with the molar ratio of sulfamate to glyoxal being 2.2:1,condensation temperature being 0?and condensation time being 48 h and pH being 3-5,the yield of HSIW is 40.28%,that of HKIW is 60.27%,and that of HNaIW is 34.67%.?5?The nitrification process of condensation product was studied.The results show that,with the material mass ratio HSIW:nitric-acid:acetic acid:acetic anhydride:ammonium nitrate being 3:5:25:10:0.5,reaction temperature being 50?and reaction time being 4 h,the highest yield of CL-20 is 1.81%.With material mass ratio HKIW:nitric-acid:acetic anhydride being 3.5:10:20,reaction temperature being 10?and reaction time being 4 h,the highest yield of CL-20 is 3.89%.With material mass ratio HKIW:nitric-acid:acetic acid:acetic anhydride:ammonium nitrate being3.5:5:10:10:0.5,reaction temperature being 30?and reaction time being 4 h,the highest yield of CL-20 is 2.72%.With material mass ratio HNaIW:nitric-acid:acetic anhydride being 3.1:5:25,reaction temperature being 50?and reaction time being 4 h,the highest yield of CL-20 is 2.46%.With material mass ratio HNaIW:nitric-acid:acetic acid:acetic anhydride:ammonium nitrate being3.1:5:15:10:0.5,reaction temperature being 50?and reaction time being 4 h,the highest yield of CL-20 is 1.62%.The results provide a theoretical scheme for designing and selecting suitable primary amine to construct CL-20 based cage skeleton,and open a new door for realizing low-cost green manufacturing of CL-20. |
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