Investigation of Ignition Delay: Novel Beta-Substituted Ethylazide Derivatives as Potential New Liquid Propellant Fuels (Preprint)

摘要

Extensive research has been directed at replacing hydrazine and its simple derivatives in liquid propellant fuel applications. While no specific replacement has been discovered, much has been learned about what types of compounds will make good fuels. One compound that has been investigated is 2- dimethylaminoethylazide (DMAZ). DMAZ is simple to prepare, and from a handling perspective is less toxic than hydrazine. Though DMAZ is hypergolic with IRFNA, there is a significant ignition delay. The explanation, based on ab-initio calculations is that the onset of ignition involves proton transfer from the acid to the amine nitrogen, and in the lowest energy conformer of DMAZ the azide group inhibits this proton transfer. This offers some insight into how one might design a fuel that overcomes these deficiencies. Either the electron distribution could be altered to allow for an enhanced interaction between the proton and the amine nitrogen, or the molecule could be altered to move the azide group away from the amine group. In either case, the chemistry would have to be done so that the advantages found with the DMAZ molecule (i.e. toxicity and energy) are not lost. While several molecules using either one approach or the other have been identified, this paper focuses on, a molecule that takes advantage of both approaches. The replacement of the tertiary amine nitrogen in DMAZ with 1,1-dimethyl hydrazine results in a molecule, 1,1-dimethyl-2- 2- azidoethyl-hydrazine (DMAEH) with a (calculated) lowest energy conformation in which the tertiary amine nitrogen is free to interact with the acidic proton at ignition. In addition to obvious steric improvements, a group with adjacent unshared electron pairs results in an enhancement of this group's nucleophilicity. Attempts at synthesizing DMAEH have ultimately failed.