Theoretical Studies And Synthesis Of Vicinal-tetrazine Energetic Compounds

Using vicinal-tetrazine-1,3-dioxide(v-TDO)as the energetic parent structure or group to obtain high-nitrogen high-energy low-sensitivity explosives by fusing with another energetic compound during molecular design is a hotspot in the area of high energy density compounds(HEDCs).In the present thesis,theoretical and computational chemistry methods were employed to study the v-TDO compounds;molecular design strategies were used to construct many v-TDO energetic compounds,the structures and properties of new targets were predicted and among which,potential candidates of HEDC were selected;the structure-properties relationships were summarized and new molecular design strategies for vicinal-tetrazine energetic compounds were suggested;synthetic studies of some v-TDO compounds were carried out.The contents of the dissertation are divided into five parts mainly:1.Furoxano-1,2,3,4-tetrazine trioxides(FTTOs),FTTO-α and FTTO-β,were designed based on furazano-1,2,3,4-tetrazine 1,3-dioxide(FTDO).Density functional theory(DFT)method was employed to study their molecular structures,detonation properties,thermal stabilities,sensitivities and decomposing pathways.FTTOs are easily decomposing to dinitroso-1,2,3,4-tetrazine 1,3-dioxide,we suggest using relatively more stable FTTO-β as a candidate to synthesize monocyclic v-TDOs and di-tetrazine tetroxides(DTTOs),the thermodynamic possibility of the proposed synthesis route to FTTO-β has been proved theoretically;2.DFT method was employed to study the compounds designed based on azole heterocycle structure,such as 1,2,3-triazolo-1,2,3,4-tetrazine 1,3-dioxides(TTDOs),pyrazolo-1,2,3,4-tetrazine 1,3-dioxides(PzTDOs),imidazolo-1,2,3,4-tetrazine 1,3-dioxides(ITDOs)and oxazolo-1,2,3,4-tetrazine 1,3-dioxides(OTDOs),among which,promising candidates for high energy low sensitivity explosives were selected by predicting their detonation properties,thermal stabilities and sensitivities;their structure-properties relationships were summarized:the position of the electron-withdrawing group such as nitro group or adjecture oxygen has considerable influences on structures’ stabilities,the negative effect will be minimized when the nitro group is substituted on the carbon atom of position 6;3.The molecular structures of benzo-1,2,3,4-tetrazine 1,3-dioxide(BTDO)and pyridino-1,2,3,4-tetrazine 1,3-dioxides(PTDOs)were studied,their electrophilicity positions were predicted by calculating the dual descriptors(DD)and condensed dual descriptors(CDD),the conclusions are in consistent with experiment results,and the structures in which the energetic groups substitute at the most electrophilicity position turn out to be more stable and have higher yields in experiment;when there is no coordinated oxygen atom in the pyridine,the eletrophilicity positions in PTDOs are still 5 and 7 positions and 7 position is the preferred one,the electrophilicity positions are under the influence of existence of coordinated oxygen and this effect is negligible when the coordinated oxygen is at the site 6 or 8;based on this conclusion,we designed 12 PTDO nitro derivatives and predicted their detonation properties,some targets were found to have achieved the energy level of RDX;4.DFT method was employed to study the relationship between the different positions of the coordinated oxygen in the six-membered high-nitrogen heterocycle fused with v-TDO structures and their molecular stabilities.The order of stabilities of target compounds with a single coordinated oxygen atom in the auxiliary ring at different positions is site 6>site 7>site 5>site 8,the order of stabilities of compounds with two coordinated oxygen atoms at different positions is sites 5 and 7>sites 6 and 8>sites 5 and 8.The rules of electrophilicity sites in six-membered high-nitrogen heterocycles fused with v-TDO structures were also studied.At most circumstances the electrophilicity sites are site 7,which is the most preferred site,and site 5.The electrophilicity sites shift when the coordinated oxygen atom is just at the site 5 or 7,and the electrophilicity sites change to site 8 when two coordinated oxygen atoms are at site 5 and site 7 respectively.Three new v-TDOs,7-nitro-triazino-1,2,3,4-tetrazine 1,3,6,8-tetraoxide(NTTTO),6,8-dinitropyrimido-1,2,3,4-tetrazine 2,4,5,7-tetraoxide(DNPTTO)and 6-nitro-1,2,3,4-tetrazine 1,3-dioxide(NTDO)were designed based on the two conclusions above and their detonation properties and stabilities were predicted.NTTTO and DNPTTO have the energy level near DTTO and CL-20,and the sensitivities lower than RDX and HMX;NTDO has reached the energy level of RDX and its sensitivity is better than low-sensitivity explosive FOX-7.The results proved that the strategies of taking positions of coordinated oxygen atoms and electrophilicity sites into consideration are practical.We suggest to take NTTTO as the alternative candidate of DTTOs for their similar detonation properties and stabilities;5.FTDO was obtained in three steps using 3,4-diaminofurazan as starting compound,the optimum conditions of the reactions were explored and the total yield is 38.8%;The optimum conditions of BTDO’s nitrification reactions were also studied by orthogonal experiments.The yields of 5-NBTDO,7-NBTDO and DNBTDO from BTDO are 34.9%,77.1%and 19.7%,respectively.