Henri Delalu

Energetic hydrazine-based salts with nitrogen-rich and oxidizing anions.

1,1,1-Trimethylhydrazinium iodide ([(CH(3))(3)N-NH(2)]I, 1) was reacted with a silver salt to form the corresponding nitrate ([(CH(3))(3)N-NH(2)][NO(3)], 2), perchlorate ([(CH(3))(3)N-NH(2)][ClO(4)], 3), azide ([(CH(3))(3)N-NH(2)][N(3)], 4), 5-amino-1H-tetrazolate ([(CH(3))(3)N-NH(2)][H(2)N-CN(4)], 5), and sulfate ([(CH(3))(3)N-NH(2)](2)[SO(4)]·2H(2)O, 6·2H(2)O) salts. The metathesis reaction of compound 6·2H(2)O with barium salts led to the formation of the corresponding picrate ([(CH(3))(3)N-NH(2)][(NO(2))(3)Ph-O], 7), dinitramide ([(CH(3))(3)N-NH(2)][N(NO(2))(2)], 8), 5-nitrotetrazolate ([(CH(3))(3)N-NH(2)][O(2)N-CN(4)], 9), and nitroformiate ([(CH(3))(3)N-NH(2)][C(NO(2))(3)], 10) salts. Compounds 1-10 were characterized by elemental analysis, mass spectrometry, infrared/Raman spectroscopy, and multinuclear NMR spectroscopy ((1)H, (13)C, and (15)N). Additionally, compounds 1, 6, and 7 were also characterized by low-temperature X-ray diffraction techniques (XRD). Ba(NH(4))(NT)(3) (NT=5-nitrotetrazole anion) was accidentally obtained during the synthesis of the 5-nitrotetrazole salt 9 and was also characterized by low-temperature XRD. Furthermore, the structure of the [(CH(3))(3)N-NH(2)](+) cation was optimized using the B3LYP method and used to calculate its vibrational frequencies, NBO charges, and electronic energy. Differential scanning calorimetry (DSC) was used to assess the thermal stabilities of salts 2-5 and 7-10, and the sensitivities of the materials towards classical stimuli were estimated by submitting the compounds to standard (BAM) tests. Lastly, we computed the performance parameters (detonation pressures/velocities and specific impulses) and the decomposition gases of compounds 2-5 and 7-10 and those of their oxygen-balanced mixtures with an oxidizer.

Metal salts of the 4,5-dicyano-2H-1,2,3-triazole anion ([C4N5]-).

Diaminomaleodinitrile was reacted at low temperatures with in situ generated nitrous acid to form 4,5-dicyano-2H-1,2,3-triazole (1) in yields above 90%. Crystalline 1 was then reacted with one equivalent of a suitable alkali or alkaline earth metal base (typically a hydroxide or a carbonate) in a polar solvent to form the corresponding alkali and alkaline earth metal salts of 4,5-dicyano-2H-1,2,3-triazole (compounds 2-9). The thermal stability of the metal salts 2-9 was assessed by differential scanning calorimetry, which showed excellent thermal stabilities up to above 350 °C. Due to the energetic character of triazole-based salts, initial safety testing was used to assess the sensitivity of compounds 2-9 towards impact, friction, electrostatic discharge and fast heating. These results revealed very low sensitivities towards all four stimuli. Additionally, compounds 2-9 were characterized by mass spectrometry, elemental analysis, infrared and Raman spectroscopy and ((1)H, (13)C and (14)N) NMR spectroscopy. We also determined the solid state structure of the 4,5-dicyano-2H-1,2,3-triazole anion of one of the alkali metal salts (4: Monoclinic, P2(1)/c, a = 9.389(1) Å, b = 10.603(1) Å, c = 6.924(1) Å, β = 102.75(1)° and V = 1036.58(3) Å(3)) and one of the alkaline earth metal salts (6: Monoclinic, P2(1)/c, a = 9.243(1) Å, b = 15.828(2) Å, c = 6.463(1) Å, β = 90.23(1)° and V = 945.5(2) Å(3)). Furthermore, we noted the hydrolysis of one of the cyano groups of the 4,5-dicyano-2H-1,2,3-triazole anion in the strontium salt 8 to form the 5-cyano-2H-1,2,3-triazole-4-carboxylic acid derivative 8b, as confirmed by X-ray studies (8b: Monoclinic, P2(1)/n, a = 6.950(1) Å, b = 17.769(1) Å, c = 13.858(1) Å, β = 92.98(1)° and V = 1709.1(1) Å(3)). Lastly, we computed the NBO and Mülliken charges for the anion of compounds 2-9 and those of the anion of compound 8b.

Salts of 1-(chloromethyl)-1,1-dimethylhydrazine and ionic liquids

The reaction of 1,1-dimethylhydrazine with excess dichloromethane led to the formation of the chloride salt of the 1-(chloromethyl)-1,1-dimethylhydrazinium cation ([(CH3)2N(CH2Cl)NH2]Cl, 1). The reaction of 1 with a suitable silver salt provided the nitrate ([(CH3)2N(CH2Cl)NH2][NO3], 2), perchlorate ([(CH3)2N(CH2Cl)NH2][ClO4], 3), azide ([(CH3)2N(CH2Cl)NH2][N3], 4), dicyanamide ([(CH3)2N(CH2Cl)NH2][N(CN)2], 5) and sulphate ([(CH3)2N(CH2Cl)NH2]2[SO4], 6) salts. Compound 6 reacted with barium 5,5′-azobistetrazolate pentahydrate (Ba[N4C–NN–CN4]·5H2O), barium dipicrate tetrahydrate (Ba[(NO2)3Ph–O]2·4H2O) and barium 5-amino-1H-tetrazolate tetrahydrate (Ba[H2N–CN4]2·4H2O) to form the corresponding metathesis products: [(CH3)2N(CH2Cl)NH2]2[N4C–NN–CN4] (7), [(CH3)2N(CH2Cl)NH2][(NO2)3Ph–O] (8) and [(CH3)2N(CH2Cl)NH2][H2N–CN4] (9). Compounds 1–9 were characterized by elemental analysis, mass spectrometry, NMR (1H and 13C) and vibrational spectroscopy (infrared and Raman). Additionally, we measured the 15N NMR spectrum of the nitrate salt 2 and identified the solid state structure of compounds 3, 6, 7 and 8 by low temperature X-ray crystallography (3: Triclinic P, a = 5.983(1) A, b = 7.502(1) A, c = 9.335(1) A; α = 93.86(1)°, β = 101.21(1)°; γ = 91.13(1)°; V = 409.8(1) A3, 6: Monoclinic C2/c, a = 11.674(2) A, b = 17.503(3) A, c = 6.616(1) A; β = 90.27(1)°; V = 1351.8(4) A3, 7: Triclinic P, a = 8.851(1) A, b = 8.872(1) A, c = 11.529(1) A; α = 80.98(1)°, β = 83.47(1)°; γ = 71.37(1)°; V = 845.4(1) A3 and 8: Monoclinic C2/c, a = 24.168(3) A, b = 7.375(1) A, c = 17.062(3) A; β = 116.19(2)°; V = 1351.8(3) A3). The solid state structure of barium dipicrate hexahydrate (Ba[(NO2)3Ph–O]2·6H2O) was also elucidated: Triclinic P, a = 6.641(1) A, b = 11.588(1) A, c = 15.033(1) A; α = 84.64(1)°, β = 80.07(1)°; γ = 86.80(1)°; V = 1133.8(1) A3. Furthermore, we studied the thermal properties of compounds 1–9 by differential scanning calorimetry (DSC). Salts 2–4, 8 and 9 fall within the category of ionic liquids. Lastly, the energetic salts were subjected to standard sensitivity tests and a software code was used to predict the detonation parameters and specific impulses of the compounds and their mixtures with an oxidizer.

Synthesis and stability of 2-tetrazenium salts

The geometry and electronic structure of (E)-N4Me4 (1) and the (E)-N4Me4H+ and the (E)-N4Me5+ cations was examined by a DFT approach. By using the B3LYP/6-31+G(d,p) model we showed that the terminal nitrogen atoms in 1 are strongly basic, as evidenced by their highly negative NBO charges in comparison to the azo nitrogen atoms. Interestingly, protonation of 1 to form the (E)-N4Me4H+ cation does not result in significant changes in the NBO charges of the protonated nitrogen atom, which is in contrast with classical views that describe tetracoordinated nitrogen atoms as being positively charged. Insight into the thermal stability of salts of the (E)-N4Me4H+ and the (E)-N4Me5+ cations was gained experimentally by DSC measurements of two salts of the (E)-N4Me4H+ cation, namely with chloride (2) and picrate (3) anions and the iodide salt of the (E)-N4Me5+ cation (4), which were synthesized by protonation of 1 with hydrochloric (2) and picric (3) acids and by methylation of 1 with methyl iodide (4), respectively. Compounds 2–4 were characterized by analytical (elemental analysis and mass spectrometry) and spectroscopic (1H/13C NMR, IR/Raman and UV spectroscopies) methods. Protonation and methylation of 1 to form the (E)-N4Me4H+ (compounds 2 and 3) and (E)-N4Me5+ (compound 4) cations, respectively, appears to occur at the terminal nitrogen atoms, in keeping with the results of the NBO analysis and the higher stabilization energy of the conformations with a protonated/methylated terminal nitrogen atom. The geometry optimization by the B3LYP/6-31+G(d,p) method points at very weak N3–N4 bonds (N4 = protonated/methylated nitrogen atom), which explains the formation of dimethylammonium picrate in the thermal decomposition of picrate salt 3 and suggests that dialkylaminium radicals (R2N+˙) are involved in the decomposition pathway.

Kinetics of the Oxidation of N-Aminopiperidine with Chloramine

The kinetics of the oxidation of N-aminopiperidine with chloramine was studied at different temperatures, with variable concentrations of the two reactants and at a pH ranging between 12 and 13.5. The reaction showed to be involving two steps: the first corresponded to the formation of a diazene intermediate, the second to the evolution of this intermediate into numerous compounds within a complex reactional chain. The rate law of the first step was determined by the Ostwald method and found to be first order with respect to each reactant. The rate constant was determined at pH 12.89 and T = 255°C: k2 = 1.15 × 105 exp(−39/RT) l mol−1 s−1 (E2 in kJ/mol). With decreasing pH value, the first exhibited acid catalysis phenomena, and diazene was converted into azopiperidine particularly faster. This created overlapping UV-absorptions between chloramine and azopiperidine, also observed in HPLC. GC/MS analyses were used to identify some of the numerous by-products formed. Their proportions are dependent of both pH and the reactants’ concentrations ratio. A reaction mechanism taking this relationship into account was suggested.

Kinetics of dehydrohalogenation ofN-chloro-3-azabicyclo[3,3,0]octane in alkaline medium. NMR and ES/MS evidence of the dimerization of 3-azabicyclo[3,3,0]oct-2-ene

The formation of 3-azabicyclo[3,3,0]oct-2-ene in the course of the synthesis of N-amino-3-azabicyclo[3,3,0]octane using the Raschig process results from the following two consecutive reactions: chlorine transfer between the monochloramine and the 3-azabicyclo[3,3,0]octane followed by a dehydrohalogenation of the substituted haloamine. The kinetics of the reaction were studied by HPLC and UV as a function of temperature (15 to 44°C), and the concentrations of NaOH (0.1 to 1 M) and the chlorinated derivative (1 to 4×10−3 M). The reaction is bimolecular (k=103×10−6 M−1 s−1; ΔH0#=89 kJ mol−1; and ΔS0#=−33.6 J mol−1 K−1) and has an E2 mechanism. The spectral data of 3-azabicyclo[3,3,0]oct-2-ene were determined. IR, NMR, and ES/MS analysis show dimerization of the water-soluble monomer into a white insoluble dimer.

Kinetic modelling of synthesis of N-aminopiperidine from hydroxylamine-O-sulfonique acid and piperidine

A new route to synthesize N-aminopiperidine (NAPP) from hydroxylamine-O-sulfonique acid (HOSA) and piperidine was described. Kinetics of the reaction was investigated to optimize the conditions of the synthesis. Since the reaction is fast, this study was carried out in a diluted medium (10−3 to 10−2 mol/l). To determine the concentration of the reaction product, NAPP was allowed to react with formaldehyde and the product was analysed by UV and HPLC techniques. The formation of NAPP is consistent with the first-order reaction to two reagents, governed by the nucleophilic substitution via SN2 mechanism. Oxidation of NAPP by HOSA was identified as the main secondary reaction which consistently reduced the yield of NAPP. A number of differential equations were elaborated and solution of these equations serves to predict the behavior of the system as a function of the reagent concentrations, pH and temperature. From the corresponding mathematical treatment a unique implicit expression was derived that characterizes the reaction medium. It was found that the [PP]0/[HOSA]0 molar ratio (p), the initial concentrations of [PP]0 and [HOSA]0, the ratio of rate constants k2/k1 and temperature are the only parameters that affect the yield of NAPP from HOSA. The results calculated from this model are in good agreement with the experimental data and they can be used to determine the optimal conditions of the reaction.

Kinetic and mechanistic study of N-aminopiperidine formation via the raschig process

Formation of N-aminopiperidine (NAPP) in the reaction of monochloramine with piperidine was studied by varying the reagents concentrations, pH and temperature. The study was carried out in diluted solutions, recording simultaneously monochloramine concentration by UV spectrophotometry at 243 nm and hydrazine concentration at 237 nm after treatment with formaldehyde. The presence of two competitive reactions: formation of NAPP and a complex parallel reaction limiting the yield of hydrazine, was established. Reaction products were characterized by GC/MS analysis. The rate constant of NAPP formation and activation parameters were determined, k1 = 56 × 10−3 M−1 s−1 (25°C) and k1 = 9.3 × 106 exp(−46.5/RT) M−1 s−1, respectively.

Synthesis and characterization of two formyl 2-tetrazenes.

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)°, β=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; β=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.

Oxidation kinetics of methylhydrazine in a strictly single-phase medium studied in reconstituted air

The oxidation of methylhydrazine (monomethylhydrazine MMH) is studied in a strictly single-phase gaseous medium, in a reconstituted surrounding atmosphere. In order to work under such conditions, a specific apparatus was assembled to monitor the evolution of the reactants through time. The reaction kinetics was studied at 50°C to avoid condensation of the water formed and for O2/MMH mole ratios between 1 and 4. Under these conditions, the partial pressures of O2 were between 0.05 and 0.18 bar (4% MMH per volume). The main reaction products were monitored through time and identified by gas chromatography coupled with mass spectrometry (GC/MS). The products were: N2, CH4, CH3-NH-N=CH2 (formaldehyde monomethylhydrazone), NH3, H2O, CH3OH, and CH2=N-N=N-CH3 (2,3,4-triazapenta-1,3-diene). The formation of nitrosamines was not observed under these experimental conditions. The rate laws related to the disappearance of the reagents were clearly established and can be described by 2 consecutive parallel reactions of order 2 whose rate constants are: k1 = 7.57 × 10−2 bar−1 min−1 and k2 = 0.5 bar−1 min−1. Analysis of the products permitted establishing an approximated balance of the global reaction.