2-Dimethylaminoethylazide

2-Dimethylaminoethylazide (DMAZ) is a liquid rocket fuel being investigated for use as a spacecraft propellent to replace the toxic, carcinogenic monomethylhydrazine.[1] It is a member of the competitive impulse non-carcinogenic hypergol (CINCH) family which were assessed as a replacement for hydrazine-derived propellants.[2][3] DMAZ was also found to be sensitive to impact, direct flame, shock wave, heat in confined space, and electrostatic discharge.[4]

2-Dimethylaminoethylazide
Names
Preferred IUPAC name
2-Azido-N,N-dimethylethan-1-amine
Other names
Dimethyl(2-azidoethyl)amine
Identifiers
3D model (JSmol)
ChemSpider
  • InChI=1S/C4H10N4/c1-8(2)4-3-6-7-5/h3-4H2,1-2H3
    Key: XIXCIVDAWWCJJR-UHFFFAOYSA-N
  • InChI=1/C4H10N4/c1-8(2)4-3-6-7-5/h3-4H2,1-2H3
    Key: XIXCIVDAWWCJJR-UHFFFAOYAI
  • CN(C)CCN=[N+]=[N-]
Properties
(CH3)2NCH2CH2N3
Molar mass 114.152 g·mol−1
Appearance Colorless liquid
Density 0.9930 g/cm3
Melting point −68.9 °C (−92.0 °F; 204.2 K)
Boiling point 135 °C (275 °F; 408 K)
Solubility Acetone, ethers, alcohols, hydrocarbons, THF
Thermochemistry
+586 cal/g
Hazards
Flash point 29.4 °C (84.9 °F; 302.5 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Formation and reactions

DMAZ is an organic azide, which is prepared by reacting the chloride of the corresponding alkyl-amine (in this case ethylamine) with sodium azide:[1]

NaN3 + NH2CH2CH2−Cl → NaCl + NH2CH2CH2−N3

Ideally, the complete combustion of DMAZ produces carbon dioxide, water, and nitrogen:

2 (CH3)2NCH2CH2N3 + 13 O2 → 8 CO2 + 10 H2O + 4 N2

Ignition delays

During their inquiry into finding alternative hypergolic fuel, a joint effort by the Aviation and Missile Research, Development, and Engineering Center (AMRDEC), the U.S. Army Research Laboratory (ARL), and the National Aeronautics and Space Administration (NASA) determined that DMAZ could perform competitively with Aerozine-50 and is less toxic than hydrazine-based fuels.[4][5] However, DMAZ-inhibited red fuming nitric acid (IRFNA) systems have demonstrated longer ignition delays than monomethylhydrazine-IRFNA systems. In an effort to address this issue, researchers synthesized the related compounds 2-azidoethanamines – 2-azido-N-methylethanamine (MMAZ) and 2-azido-N-cyclopropylethanamine (CPAZ) in hopes of enhancing the reactivity of DMAZ's amine nitrogen to reduce ignition delays. MMAZ is not hypergolic, while CPAZ is hypergolic.[6]

According to research conducted by Army Research Laboratory, the azido group in DMAZ's lowest energy structure will prevent the transfer of protons from nitric acid to the amine lone pair acid, a chemical reaction that may be associated with a rate-limiting step in DMAZ-IRFNA ignition.[6]

However, according to a 2014 ARL report, a correlation between compound basicities and ignition delays was not observed, which indicates that the proton transfer from nitric acid to DMAZ's amine may not be a rate-controlling step in the ignition process of DMAZ-IRFNA systems.[7]

References
  1. Mellor, B. (2004). "A Preliminary Technical Review of DMAZ: A Low-Toxicity Hypergolic Fuel". Proceedings of the 2nd International Conference on Green Propellants for Space Propulsion. Vol. 557. p. 22. Bibcode:2004ESASP.557E..22M.
  2. "Army Develops New Fuel". Spacedaily.com. February 23, 2000. Retrieved July 12, 2014.
  3. Michael J. McQuaid (April 2004). "The Structure of Secondary 2-Azidoethanamines: A Hypergolic Fuel vs. a Nonhypergolic Fuel". Defense Technical Information Center. Army Research Laboratory.
  4. Xie, Hui; Mu, Xiaogang; Zhang, Yue; Wang, Xuanjun (May 8, 2017). "Theory investigation progress of DMAZ". AIP Conference Proceedings. 1839 (1): 020016. Bibcode:2017AIPC.1839b0016X. doi:10.1063/1.4982381.
  5. McQuaid, Michael (December 2003). "Computationally Based Measures of Amine Azide Basicity and Their Correlation With Hypergolic Ignition Delays". Defense Technical Information Center. Army Research Laboratory.
  6. McQuaid, Michael (September 2002). "Computational Characterization of 2-Azidocycloalkanamines: Notional Variations on the Hypergol 2-Azido-N,N-Dimethylethanamine (DMAZ)". Defense Technical Information Center. Army Research Laboratory.
  7. Chen, Chiung-Chu; McQuaid, Michael (January 2014). "A Thermochemical Kinetic-Based Study of Ignition Delays for 2-Azidoethanamine-Red Fuming Nitric Acid Systems: 2 Azido-N-Methylethanamine (MMAZ) Vs. 2 Azido-N,N-Dimethylethanamine (DMAZ)". Defense Technical Information Center. Army Research Laboratory.
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