Synthesis and Ignition Properties Research of 1,5-Diazabicyclo[3.1.0]Hexane Type Compounds as Potential Green Hypergolic Propellants

Abstract

1,5-Diazabicyclo[3.1.0]hexane type compounds (DABHCs) were found as promising liquid hypergolic compounds. The synthesis process and purification of DABHCs, 1,5-diazabicyclo[3.1.0]hexane (DABH), 6-methyl-1,5-diazabicyclo[3.1.0]hexane (MDABH), 6-ethyl-1,5-diazabicyclo[3.1.0]hexane (EDABH), and 6,6-dimethyl-1,5-diazabicyclo[3.1.0]hexane (DDABH) were optimized. The densities of DABHCs were over 1.0 g/mL, and the viscosities of DABHCs were about 2.40–2.63 mPa·s. The boiling points of DABHCs exhibited that they were less volatile, and the freezing points of DABHCs varied considerably for different alkylation. The LD50 predicted values of DABHCs were within 1605.62–4865.43 mg/kg, which demonstrated that DABHCs were grade IV, slightly poisonous, or grade V, nontoxic, compounds according to the Globally Harmonized System of Classification and Labeling of Chemicals (GHS). In addition, the heats of formation of DABHCs were calculated as 129.2–276.2 kJ/mol, higher than those of monomethyl hydrazine, unsymmetrical dimethyl hydrazine, and hydrazine. The ignition delay time of DABH with nitrogen tetroxide was 1 ms, and the ignition delay times of other alkyl substituted DABHCs were 4–11 ms, which indicated the promising application of DABHCs as hypergolic propellants.