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

Abstract

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) Å, b = 7.502(1) Å, c = 9.335(1) Å; α = 93.86(1)°, β = 101.21(1)°; γ = 91.13(1)°; V = 409.8(1) ų, 6: Monoclinic C₂/c, a = 11.674(2) Å, b = 17.503(3) Å, c = 6.616(1) Å; β = 90.27(1)°; V = 1351.8(4) ų, 7: Triclinic P, a = 8.851(1) Å, b = 8.872(1) Å, c = 11.529(1) Å; α = 80.98(1)°, β = 83.47(1)°; γ = 71.37(1)°; V = 845.4(1) ų and 8: Monoclinic C2/c, a = 24.168(3) Å, b = 7.375(1) Å, c = 17.062(3) Å; β = 116.19(2)°; V = 1351.8(3) ų). The solid state structure of barium dipicrate hexahydrate (Ba[(NO₂)₃Ph–O]₂·6H₂O) was also elucidated: Triclinic P, a = 6.641(1) Å, b = 11.588(1) Å, c = 15.033(1) Å; α = 84.64(1)°, β = 80.07(1)°; γ = 86.80(1)°; V = 1133.8(1) ų. 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.