Unsymmetrical dimethylhydrazine (abbreviated as UDMH; also known as 1,1-dimethylhydrazine, heptyl or Geptil) is a chemical compound with the formula H2NN(CH3)2 that is primarily used as a rocket propellant.[4] At room temperature, UDMH is a colorless liquid, with a sharp, fishy, ammonia-like smell typical of organic amines. Samples turn yellowish on exposure to air and absorb oxygen and carbon dioxide. It is miscible with water, ethanol, and kerosene. At concentrations between 2.5% and 95% in air, its vapors are flammable. It is not sensitive to shock.
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| Names | |||
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| Preferred IUPAC name
1,1-Dimethylhydrazine[1] | |||
| Other names
Dimazine
1,1-Dimethyldiazane | |||
| Identifiers | |||
3D model (JSmol)
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| 605261 | |||
| ChEBI | |||
| ChemSpider | |||
| ECHA InfoCard | 100.000.287 | ||
| EC Number |
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| KEGG | |||
| MeSH | dimazine | ||
PubChem CID
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| RTECS number |
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| UNII | |||
| UN number | 1163 | ||
CompTox Dashboard (EPA)
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| Properties | |||
| H2NN(CH3)2 | |||
| Appearance | Colorless liquid | ||
| Odor | Ammoniacal, fishy | ||
| Density | 791 kg m−3 (at 22 °C) | ||
| Melting point | −57 °C; −71 °F; 216 K | ||
| Boiling point | 64.0 °C; 147.1 °F; 337.1 K | ||
| Miscible[2] | |||
| Vapor pressure | 13.7 kPa (at 20 °C) | ||
Refractive index (nD)
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1.4075 | ||
| Thermochemistry | |||
Heat capacity (C)
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164.05 J K−1 mol−1 | ||
Std molar
entropy (S⦵298) |
200.25 J K−1 mol−1 | ||
Std enthalpy of
formation (ΔfH⦵298) |
48.3 kJ mol−1 | ||
Std enthalpy of
combustion (ΔcH⦵298) |
−1982.3 – −1975.1 kJ mol−1 | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards
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Carcinogen, spontaneously ignites on contact with oxidizers | ||
| GHS labelling: | |||
    
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| Danger | |||
| H225, H301, H314, H331, H350, H411 | |||
| P210, P261, P273, P280, P301+P310 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | −10 °C (14 °F; 263 K) | ||
| 248 °C (478 °F; 521 K) | |||
| Explosive limits | 2–95% | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
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LC50 (median concentration)
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| NIOSH (US health exposure limits): | |||
PEL (Permissible)
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TWA 0.5 ppm (1 mg/m3) [skin][2] | ||
REL (Recommended)
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Ca C 0.06 ppm (0.15 mg/m3) [2 hr][2] | ||
IDLH (Immediate danger)
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Ca [15 ppm][2] | ||
| Related compounds | |||
Related compounds
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Symmetrical dimethylhydrazine (1,2-dimethylhydrazine) also exists, but it is not as useful.[5] UDMH can be oxidized in air to form many different substances, including toxic ones.[6][7][8]
Production
editUDMH is produced industrially by two routes.[5] Based on the Olin Raschig process, one method involves reaction of monochloramine with dimethylamine giving 1,1-dimethylhydrazinium chloride:
- (CH3)2NH + NH2Cl → (CH3)2NNH2 ⋅ HCl
In the presence of suitable catalysts, acetylhydrazine can be N-dimethylated using formaldehyde and hydrogen to give the N,N-dimethyl-N'-acetylhydrazine, which can subsequently be hydrolyzed:
- CH3C(O)NHNH2 + 2CH2O + 2H2 → CH3C(O)NHN(CH3)2 + 2H2O
- CH3C(O)NHN(CH3)2 + H2O → CH3COOH + H2NN(CH3)2
Uses
editUDMH is often used in hypergolic rocket fuels as a bipropellant in combination with the oxidizer nitrogen tetroxide and less frequently with IRFNA (inhibited red fuming nitric acid) or liquid oxygen.[9] UDMH is a derivative of hydrazine and is sometimes referred to as a hydrazine. As a fuel, it is described in specification MIL-PRF-25604 in the United States.[10]
UDMH is stable and can be kept loaded in rocket fuel systems for long periods, which makes it appealing for use in many liquid rocket engines, despite its cost. In some applications, such as the OMS in the Space Shuttle or maneuvering engines, monomethylhydrazine is used instead due to its slightly higher specific impulse. In some kerosene-fueled rockets, UDMH functions as a starter fuel to start combustion and warm the rocket engine prior to switching to kerosene.
UDMH has higher stability than hydrazine, especially at elevated temperatures, and can be used as its replacement or together in a mixture. UDMH is used in many European, Russian, Indian, and Chinese rocket designs. The Russian SS-11 Sego (aka 8K84) ICBM, SS-19 Stiletto (aka 15A30) ICBM, Proton, Kosmos-3M, R-29RMU2 Layner, R-36M, Rokot (based on 15A30) and the Chinese Long March 2 are the most notable users of UDMH (which is referred to as "heptyl" (codename from Soviet era)[citation needed] by Russian engineers[11]). The Titan, GSLV, and Delta rocket families use a mixture of 50% hydrazine and 50% UDMH, called Aerozine 50, in different stages.[12] There is speculation that it is the fuel used in the ballistic missiles that North Korea has developed and tested in 2017.[13]
Safety
editHydrazine and its methyl derivatives are toxic but LD50 values have not been reported.[14] It is a precursor to dimethylnitrosamine, which is carcinogenic.[15] According to scientific data, usage of UDMH in rockets at Baikonur Cosmodrome has had adverse effects on the environment.[16]
See also
editReferences
edit- ^ "dimazine – Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification. Retrieved 21 February 2012.
- ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0227". National Institute for Occupational Safety and Health (NIOSH).
- ^ "1,1-Dimethylhydrazine". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
- ^ Semenkov, Ivan; Koroleva, Tatyana (1 December 2022). "Review on the environmental impact of emissions from space launches: a case study for areas affected by the Russian space programme". Environmental Science and Pollution Research. 29 (60): 89807–89822. Bibcode:2022ESPR...2989807S. doi:10.1007/s11356-022-23888-8. ISSN 1614-7499. PMID 36346528. S2CID 253396676.
- ^ a b Schirmann, Jean-Pierre; Bourdauducq, Paul (2001). "Hydrazine". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a13_177. ISBN 3-527-30673-0.
- ^ Aleksey Milyushkin, Anastasia Karnaeva (2023). "Unsymmetrical dimethylhydrazine transformation products: A review". Science of the Total Environment. 891: 164367. Bibcode:2023ScTEn.89164367M. doi:10.1016/j.scitotenv.2023.164367. PMID 37236454. S2CID 258899003.
- ^ Ul'yanovskii, Nikolay V.; Lakhmanov, Dmitry E.; Pikovskoi, Ilya I.; Falev, Danil I.; Popov, Mark S.; Kozhevnikov, Alexander Yu.; Kosyakov, Dmitry S. (15 July 2020). "Migration and transformation of 1,1-dimethylhydrazine in peat bog soil of rocket stage fall site in Russian North". Science of the Total Environment. 726: 138483. Bibcode:2020ScTEn.72638483U. doi:10.1016/j.scitotenv.2020.138483. ISSN 0048-9697. PMID 32315849. S2CID 216073493.
- ^ Koroleva, T. V.; Semenkov, I. N.; Lednev, S. A.; Soldatova, O. S. (1 February 2023). "Unsymmetrical Dimethylhydrazine (UDMH) and Its Transformation Products in Soils: A Review of the Sources, Detection, Behavior, Toxicity, and Remediation of Polluted Territories". Eurasian Soil Science. 56 (2): 210–225. Bibcode:2023EurSS..56..210K. doi:10.1134/S1064229322602001. ISSN 1556-195X. S2CID 257903133.
- ^ Semenkov, Ivan; Koroleva, Tatyana (1 December 2022). "Review on the environmental impact of emissions from space launches: a case study for areas affected by the Russian space programme". Environmental Science and Pollution Research. 29 (60): 89807–89822. Bibcode:2022ESPR...2989807S. doi:10.1007/s11356-022-23888-8. ISSN 1614-7499. PMID 36346528. S2CID 253396676.
- ^ "PERFORMANCE SPECIFICATION PROPELLANT, uns-DIMETHYLHYDRAZINE (MIL-PRF-25604F)". ASSIST Database Quicksearch. 11 March 2014. Retrieved 26 May 2020.
- ^ "Following Russian rocket explosion, experts warn of 'major contamination'". 2 July 2013.
- ^ Clark, John D. (1972). Ignition! An Informal History of Liquid Rocket Propellants. Rutgers University Press. p. 45. ISBN 0-8135-0725-1.
- ^ Broad, William J.; Sanger, David E. (17 September 2017). "The Rare, Potent Fuel Powering North Korea's Weapons". The New York Times.
- ^ "unsym-Dimethylhydrazine Safedy data" (4 ed.). Archived from the original on 6 July 2018. Retrieved 23 January 2018.
- ^ Gangadhar Choudhary, Hugh Hansen (1998). "Human health perspective of environmental exposure to hydrazines: A review". Chemosphere. 37 (5): 801–843. Bibcode:1998Chmsp..37..801C. doi:10.1016/S0045-6535(98)00088-5. PMID 9717244.
- ^ Abdrazak, P. Kh; Musa, K. Sh (21 June 2015). "The impact of the cosmodrome 'Baikonur' on the environment and human health". International Journal of Biology and Chemistry. 8 (1): 26–29. doi:10.26577/2218-7979-2015-8-1-26-29. Archived from the original on 8 August 2016. Retrieved 2 August 2016 – via ijbch.kaznu.kz.