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Unsymmetrical dimethylhydrazine

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Unsymmetrical dimethylhydrazine
Skeletal formula of unsymmetrical dimethylhydrazine with some implicit hydrogens shown
Skeletal formula of unsymmetrical dimethylhydrazine with some implicit hydrogens shown
Ball and stick model of unsymmetrical dimethylhydrazine
Ball and stick model of unsymmetrical dimethylhydrazine
Names
Preferred IUPAC name
1,1-Dimethylhydrazine[1]
Other names
Dimazine
Identifiers
3D model (JSmol)
605261
ChEBI
ChemSpider
ECHA InfoCard 100.000.287 Edit this at Wikidata
EC Number
  • 200-316-0
KEGG
MeSH dimazine
RTECS number
  • MV2450000
UNII
UN number 1163
  • InChI=1S/C2H8N2/c1-4(2)3/h3H2,1-2H3 ☒N
    Key: RHUYHJGZWVXEHW-UHFFFAOYSA-N ☒N
  • CN(C)N
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)
1.4075
Thermochemistry
164.05 J K−1 mol−1
200.25 J K−1 mol−1
48.3 kJ mol−1
−1982.3 – −1975.1 kJ mol−1
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Carcinogen, spontaneously ignites on contact with oxidizers
GHS labelling:
GHS02: Flammable GHS05: Corrosive GHS06: Toxic GHS08: Health hazard GHS09: Environmental hazard
Danger
H225, H301, H314, H331, H350, H411
P210, P261, P273, P280, P301+P310
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
4
3
1
Flash point −10 °C (14 °F; 263 K)
248 °C (478 °F; 521 K)
Explosive limits 2–95%
Lethal dose or concentration (LD, LC):
  • 122 mg kg−1 (oral, rat)
  • 1.06 g kg−1 (dermal, rabbit)
  • 252 ppm (rat, 4 hr)
  • 172 ppm (mouse, 4 hr)
  • 392 ppm (hamster, 4 hr)
  • 3580 ppm (dog, 15 min)
  • 1410 ppm (rat, 1 hr)
  • 981 ppm (dog, 1 hr)[3]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 0.5 ppm (1 mg/m3) [skin][2]
REL (Recommended)
Ca C 0.06 ppm (0.15 mg/m3) [2 hr][2]
IDLH (Immediate danger)
Ca [15 ppm][2]
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Unsymmetrical dimethylhydrazine (UDMH; 1,1-dimethylhydrazine, heptyl or codenamed Geptil) is a chemical compound with the formula H2NN(CH3)2 that is used as a rocket propellant.[4] It is a colorless liquid, with a sharp, fishy, ammonia-like smell typical for organic amines. Samples turn yellowish on exposure to air and absorb oxygen and carbon dioxide. It is miscible with water, ethanol, and kerosene. In concentration between 2.5% and 95% in air, its vapors are flammable. It is not sensitive to shock. Symmetrical dimethylhydrazine (1,2-dimethylhydrazine) is also known but is not as useful.[5] UDMH can be oxidized in air to form many different substances, including toxic ones.[6][7][8]

Production[edit]

UDMH 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[edit]

UDMH 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 2F 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[edit]

Hydrazine 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[edit]

References[edit]

  1. ^ "dimazine – Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification. Retrieved 21 February 2012.
  2. ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0227". National Institute for Occupational Safety and Health (NIOSH).
  3. ^ "1,1-Dimethylhydrazine". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. ^ 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.
  5. ^ 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.
  6. ^ Aleksey Milyushkin, Anastasia Karnaeva (2023). "Unsymmetrical dimethylhydrazine transformation products: A review". Science of the Total Environment. 891: 164367. Bibcode:2023ScTEn.891p4367M. doi:10.1016/j.scitotenv.2023.164367. PMID 37236454. S2CID 258899003.
  7. ^ 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.726m8483U. doi:10.1016/j.scitotenv.2020.138483. ISSN 0048-9697. PMID 32315849. S2CID 216073493.
  8. ^ 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.
  9. ^ 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.
  10. ^ "PERFORMANCE SPECIFICATION PROPELLANT, uns-DIMETHYLHYDRAZINE (MIL-PRF-25604F)". ASSIST Database Quicksearch. 11 March 2014. Retrieved 26 May 2020.
  11. ^ "Following Russian rocket explosion, experts warn of 'major contamination'". 2 July 2013.
  12. ^ Clark, John D. (1972). Ignition! An Informal History of Liquid Rocket Propellants. Rutgers University Press. p. 45. ISBN 0-8135-0725-1.
  13. ^ Broad, William J.; Sanger, David E. (17 September 2017). "The Rare, Potent Fuel Powering North Korea's Weapons". The New York Times.
  14. ^ "unsym-Dimethylhydrazine Safedy data" (4 ed.). Archived from the original on 6 July 2018. Retrieved 23 January 2018.
  15. ^ 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.
  16. ^ 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.

External links[edit]