Synthesis And Study Of Pentazole And Its Derivatives

As a member of all-nitrogen energetic materials,pentazole has unique physical and chemical properties.The synthesis of pentazole helps to develop all-nitrogen energetic materials,so it has great significance.A series of explorations were carried out to obtain pentazole.3.5-dimethyl-4-hydroxy aniline hydrochloride was synthesized by using 4-aminobenzene sulfonic acid and 2.6-dimethyl phenol as raw materials via diazotization.condensation and hydrolysis reaction.Then reaction method was optimized for energy saving,operative difficulty reducing.The yield was increased from 67.1%to 70.2%.3,5-dimethyl-4-hydroxy phenyl-pentazole which is stable at low temperature was synthesized with a yield of 60.8%from 3,5-dimethyl-4-hydroxy aniline hydrochloride.The side reaction was unavoidable and the best reaction temperature was-45 ℃ according to the results of orthogonal experiment.The stability of the product was studied,and its half-life was 35 min at 25 ℃.Synthetic exploration of cutting off the C-N bond of 3.5-dimethyl-4-hydroxy phenyl-pentazole was conducted by adding the transition metal salts and oxidanst to the reaction system.It showed that a small amount of pentazole anion was synthesized by using methanol as solvent,ferrous salts as catalyst,and m-chloro-peroxybenzoicacid as oxidant.In order to maximize the use of 3,5-dimethyl-4-hydroxy phenyl-pentazole and increase the productivity,the reaction conditions were optimized.Pentazole solution was characterized by mass spectrometry.NMR,IR and UV spectra.As experimental results showed,pentazole does not own UV absorption in the wavelength range of 190～400 nm.and the infrared absorption peak is about 1200 cm-1.It could be judged that pentazole exists as HN5 which would ionize to H+ and N5-in solution.Nitrogen atoms in the pentazole are in the same chemical environment and on one plane.The stability test showed that it could be stable for a long time at-50 ℃ and above 60 minutes at 25 ℃.Furthermore,synthetic explorations of pentazole derivatives were preformed by using aminopyridine,aromatic amines with different substituents and aryl azo compounds as raw materials.The synthetic experiments of pyridyl-pentazole were all failed,and it was consiedred that the electron-withdrawing groups such as pyridine group is not conductive to the stability of the pentazole.4-hydroxy phenyl-pentazole was successfully synthesized,but the reaction yield and stability were not as good as 3,5-dimethyl-4-hydroxy phenyl-pentazole.2-hydroxy phenyl-pentazole could not be obtained due to steric hindrance.Azoxybenzene was converted to CIS configuration under UV irradiation,which couled react with azidotrimethylsilane to get an added product.But this product was quickly resolved at room temperature.