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1,1,4,4-Tetramethyl-2-tetrazene (TMTZ) is considered as a prospective replacement for toxic hydrazines used in liquid rocket propulsion. The heat of formation of TMTZ was computed and measured, giving values well above those of the hydrazines commonly used in propulsion. This led to a predicted maximum Isp of 337 s for TMTZ/N2 O4 mixtures, which is a value comparable to that of monomethylhydrazine. We found that TMTZ has a vapor pressure well below that of liquid hydrazines, and it is far less toxic. Finally, an improved synthesis is proposed, which is compatible with existing industrial production facilities after minor changes. TMTZ is thus an attractive liquid propellant candidate, with a performance comparable to hydrazines but a lower vapor pressure and toxicity.

N-aminopiperidine (NAPP) belongs to a large family of compounds, namely the cyclic alkylhydrazines, used as precursors for different targets in fine chemicals, such as pharmaceuticals and cosmetics. The formation of NAPP via the Raschig process by reacting piperidine (C5H10NH, PP) with monochloramine (NH2Cl) involves many side-reactions because of the reactivity of the latter. An exhaustive kinetic model, which reflects the rate of NAPP formation and that of side-reactions occurring during the synthesis of NAPP, was established. Additionally, a comparative study of theoretical and experimental concentration-time curves permitted to verify the accuracy of the model in a diluted medium. Moreover, the established kinetic model allowed to define the optimal conditions for NAPP synthesis in a concentrated medium, by varying the reactants concentrations, [PP]/[NH2Cl] ratio, pH and temperature. Hence, the application of the kinetic model enabled to optimize the reaction in view of its transfer to a continuous 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, k 1 = 56 × 10−3 M−1 s−1 (25°C) and k 1 = 9.3 × 106 exp(−46.5/RT) M−1 s−1, respectively.

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.

1,1-Dimethylhydrazine can be readily alkylated with bromoacetonitrile to form 1-cyanomethyl-1,1-dimethylhydrazinium bromide ([(CH(3))(2)N(CH(2)CN)NH(2)]Br, 1). The metathesis reaction of compound 1 led to the formation of a new family of energetic salts based on the [(CH(3))(2)N(CH(2)CN)NH(2)](+) cation and nitrate (2), perchlorate (3), azide (4), 5-aminotetrazolate ([H(2)N-CN(4)](-), 5), 5,5'-azobistetrazolate ([N(4)C-N=N-CN(4)](2-), 7), and picrate (8) anions. The new materials were characterized by elemental analysis, mass spectrometry, and (multinuclear) NMR and vibrational (infrared and Raman) spectroscopies. Additionally, the molecular structure of the [(CH(3))(2)N(CH(2)CN)NH(2)](+) cation in compounds 1, 3, and 8 and that of sodium 5,5'-azobistetrazolate octahydrate (NaZT·8H(2)O) were solved by X-ray diffraction techniques. The hydrogen-bonding networks found in the structure of salts 1, 3, 8, and NaZT·8H(2)O are described using graph-set analysis. The melting and decomposition points of the new compounds were determined by differential scanning calorimetry, and insight into their sensitivity towards impact, friction, and electrostatics was gained by submitting the materials to standard tests. Furthermore, we estimated some performance parameters of interest and predicted the decomposition gases formed upon decomposition of salts 2-8 and of mixtures with an oxidizer. The interesting thermal, sensitivity, and performance properties of some of the compounds described in this work make them attractive towards a prospective energetic application.

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 k 2/k 1 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.

(1E,2E)-2,2′-dipyridylglyoxime (1) was synthesized by a literature method involving the reaction of 2,2′-pyridyl with an excess of hydroxylammonium chloride and sodium hydroxide in distilled water. 1 was characterized by elemental analysis, melting point, mass spectrometry, and NMR (1H and 13C) spectroscopy. In addition, the crystal structure of 1 was determined by low temperature X-ray analysis. 1 crystallizes in the monoclinic space group P21/n with four formula units in the unit cell and the following unit cell parameters: a = 6.269(1) A, b = 10.258(1) A, c = 9.132(1) A, β = 107.59(1)°, and V = 559.7(1) A3. Strong OċN hydrogen bonds link the molecules of 1, forming three-dimensional hydrogen-bonded networks; whereas the unclassical CċO hydrogen bonds result in the formation of C1,1(9) and C2,2(18) infinite chains and dimmer pairs with the graph-set descriptor R2,2(16). Lastly, the structure of 1 was fully optimized using DFT calculations (B3LYP/6-31+G(d,p)) and the NBO and Mulliken charges were calculated at the same level of theory. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 23:59–65, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20752

The reduction of N-chloro-3-azabicyclo[3.3.0]octane with sodium borohydride at different pH values and variable concentrations of the haloamine and reducing agent was studied. The reaction was found to be second order and exhibited a specific acid catalysis. The enthalpy and entropy of activation were determined at pH 12.89. A mathematical treatment of the kinetic data allowed a complete characterization of the final state and the determination of percentage of haloamine reduced as a function of temperature, [NaBH4]/[haloamine] ratio, arid pH. A reaction mechanism is proposed.

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.

International audience; 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 = 25°C: k2 = 1.15  105 exp(-39/RT) M-1 s-1 (E2 in kJ mol-1) With decreasing pH value, the first step 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.

International audience; The use of ab initio and DFT methods to calculate the enthalpies of formation of solid ionic compounds is described. The results obtained from the calculations are then compared with those from experimental measurements on nitrogen-rich salts of the 2,2-dimethyltriazanium cation (DMTZ) synthesized in our laboratory and on other nitrogen-rich ionic compounds. The importance of calculating accurate volumes and lattice enthalpies for the determination of heats of formation is also discussed. Furthermore, the crystal structure and hydrogen-bonding networks of the nitroformate salt of the DMTZ cation is described in detail. Lastly, the theoretical heats of formation were used to calculate the specific impulses (I-sp) of the salts of the DMTZ cation in view of a prospective application in propellant formulations.

Amination of 1,1-dimethylhydrazine with NH2 Cl or hydroxylamine-O-sulfonic acid yields 2,2-dimethyltriazanium (DMTZ) chloride (3) and sulphate (4), respectively. The DMTZ cation was paired with the nitrogen-rich anions 5-aminotetrazolate (5), 5-nitrotetrazolate (6), 5,5'-azobistetrazolate (7), and azide (8), yielding a new family of energetic salts. The synthesis was carried out by metathesis reactions of salts 3 or 4 and a suitable silver or barium salt. To minimize the risks involved when using heavy metal salts, we used electrodialysis for the synthesis of azide 8, which avoids the use of highly sensitive species. The DMTZ derivatives were characterized by IR and multinuclear NMR spectroscopy, elemental analysis, and X-ray diffraction. Thermal stabilities were measured using DSC analysis and their sensitivities towards classical stimuli were determined using standard tests. Lastly, the relationship between hydrogen bonding in the solid state and sensitivity is discussed.

We synthesized nitrosamines (R2N-NO) with R = iPr (1), nPr (2), nBu (3), and hydroxyethyl (4) from the amine using sodium nitrite/p-toluenesulfonic acid in CH2Cl2. The rate of formation of 1-4 increases in the direction iPr

The synthesis of high-grade chloramine was studied starting from sodium hypochlorite solutions containing 25% in NaOCl. The reagents at 100 chlorometric degrees are relatively stable and lose approximately 1.4° by 24 h at 17°C. They present a temperature of crystallization of 14.2°C (precipitation of NaOCl·5H2O) but it is possible to use them at −20°C in undercooling state. To obtain quantitative yields, it is necessary to neutralize the totality of hydroxide ions generated by the reaction and to operate below −10°C in order to limit oxidation of chloramine by the hypochlorite ions. The addition of an acceptor soluble salt is the most appropriate solution because it regenerates ammonia as soon as it is consumed and stabilizes chloramine by maintaining the pH around 10. The ammoniacal combinations NH4NO3–NH4Cl–NH3–H2O and NH4NO3–NH3–H2O are compatible and allow to operate in monophasic medium until −30°C. The yields are close to 95% with a titre in NH2Cl of 2.3 M (11.4%). Experiments carried out in continuous rating lead to a monochloramine solution of 2 M.

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) A, b=8.714(1) A, c=13.830(2) A; α=107.35(1)°, β=90.53(1)°, γ=103.33(1)°; V(UC) =668.9(2) A(3); Z=4; ρ(calc)=1.292 cm(-3). Compound 3: monoclinic; space group P2(1)/c; a=5.840(2) A, b=7.414(3) A, c=8.061(2) A; β=100.75(3)°; V(UC)=342(2) A(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.

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.

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.

High-grade chloramine is prepared in batch and in continuous mode starting from mixed ammoniacal solutions and hypochlorite at hundred chlorometric degrees.

Intermediate and final products of the oxidation of monomethylhydrazine by dioxygen are studied using an original device which allows analysis of the gaseous medium under strictly monophasic conditions.