RESUMO
Satellite propulsion uses liquid mono or bi-propellants composed of a hydrazine in combination with a strong oxidant. However, hydrazines are highly toxic. As a result, many research efforts for more environmentally compatible propellants have been made over the past decade. In this study we evidence green formulations that retain high propulsive performances. They are based on the dinitramide anion. From an initial library of 37 ammonium dinitramides 3 best candidates were selected after evaluation of their potential syntheses, calculated theoretical performances, experimental synthesis optimizations and decomposition temperatures. These three salts were then formulated to obtain acceptable sensitivities and melting points, which eventually led to only one formulation being retained: a 40 : 60 mixture of dimethylammonium dinitramide and ammonium dinitramide phlegmatized by 10 % of glycerol.
RESUMO
The synthesis of two formyl 2-tetrazenes, namely, (E)-1-formyl-1,4,4-trimethyl-2-tetrazene (2) and (E)-1,4-diformyl-1,4-dimethyl-2-tetrazene (3), by oxidation of (E)-1,1,4,4-tetramethyl-2-tetrazene (1) using potassium permanganate in acetone solution is presented. Compound 3 was also synthesized in an improved yield from the oxidation of 1-formyl-1-methylhydrazine (4a) using potassium permanganate in acetone. Both compounds 2 and 3 were characterized by analytical (elemental analysis, GC-MS) and spectroscopic methods ((1)H, (13)C, and (15)N NMR spectroscopy, and IR and Raman spectroscopy). In addition, the solid-state structures of the compounds were confirmed by low-temperature X-ray analysis. (Compound 2: triclinic; space group P-1; a=5.997(1) Å, b=8.714(1) Å, c=13.830(2) Å; α=107.35(1)°, ß=90.53(1)°, γ=103.33(1)°; V(UC) =668.9(2) Å(3); Z=4; ρ(calc)=1.292 cm(-3). Compound 3: monoclinic; space group P2(1)/c; a=5.840(2) Å, b=7.414(3) Å, c=8.061(2) Å; ß=100.75(3)°; V(UC)=342(2) Å(3); Z=2; ρ(calc)=1.396 g cm(-3).) The vibrational frequencies of compounds 2 and 3 were calculated using the B3LYP method with a 6-311+G(d,p) basis set. We also computed the natural bond orbital (NBO) charges using the rMP2/aug-cc-pVDZ method and the heats of formation were determined on the basis of their electronic energies. Furthermore, the thermal stabilities of these compounds, as well as their sensitivity towards classical stimuli, were also assessed by differential scanning calorimetry and standard BAM tests, respectively. Lastly, the attempted synthesis of (E)-1,2,3,4-tetraformyl-2-tetrazene (6) is also discussed.
