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]
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| Names | |||
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| Preferred IUPAC name
2-Azido-N,N-dimethylethan-1-amine | |||
| Other names
Dimethyl(2-azidoethyl)amine
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| Identifiers | |||
3D model (JSmol)
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| ChemSpider | |||
PubChem CID
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CompTox Dashboard (EPA)
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| 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 | |||
Std enthalpy of
formation (ΔfH⦵298) |
+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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Formation and reactions
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DMAZ is an organic azide, which is prepared by reacting the chloride of the corresponding alkyl-amine (in this case dimethyl ethylamine) with sodium azide:[1]
- NaN3 + N(CH3)2CH2CH2−Cl → NaCl + N(CH3)2CH2CH2−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
editDuring 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
edit- ^ a b 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.
- ^ "Army Develops New Fuel". Spacedaily.com. February 23, 2000. Retrieved July 12, 2014.
- ^ 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.
- ^ a b 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.
- ^ 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.
- ^ a b 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.
- ^ 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.