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Unsymmetrical dimethylhydrazine

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Unsymmetrical dimethylhydrazine (UDMH; 1,1-dimethylhydrazine) is a chemical compound with the formula H2NN(CH3)2. 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 mixes completely with water, ethanol, and kerosene. In concentration between 2.5% and 95% in air, its vapors are flammable. It is not sensitive to shock. 1,2-Dimethylhydrazine (CH3NHNHCH3) is also known but is not as useful.[4]

Unsymmetrical dimethylhydrazine
Skeletal formula of unsymmetrical dimethylhydrazine with some implicit hydrogens shown
Ball and stick model of unsymmetrical dimethylhydrazine
IUPAC name
Other names
3D model (JSmol)
ECHA InfoCard 100.000.287
EC Number
  • 200-316-0
MeSH dimazine
RTECS number
  • MV2450000
UN number 1163
Molar mass 60.100 g·mol−1
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
Vapor pressure 13.7 kPa (at 20 °C)
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
Main hazards carcinogen, spontaneously ignites on contact with oxidizers
GHS pictograms GHS02: Flammable GHS05: Corrosive GHS06: Toxic GHS08: Health hazard GHS09: Environmental hazard
GHS signal word DANGER
H225, H301, H314, H331, H350, H411
P210, P261, P273, P280, P301+310
NFPA 704
Flammability code 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. gasolineHealth code 4: Very short exposure could cause death or major residual injury. E.g. VX gasReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no codeNFPA 704 four-colored 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):
  • 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]
US health exposure limits (NIOSH):
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 ☑Y☒N ?)
Infobox references


UDMH is produced industrially by two routes.[4] One, based on the Olin Raschig process, involves reaction of monochloramine with dimethylamine. This method gives the hydrochloride of the hydrazine:

(CH3)2NH + NH2Cl → (CH3)2NNH2 + HCl

Alternatively, acetylhydrazine can be N-methylated using formaldehyde to give the N,N-dimethyl-N'-acetylhydrazine, which can subsequently be hydrolyzed:

CH3C(O)NHNH2 + 2 CH2O + 2 H2 → CH3C(O)NHN(CH3)2 + 2 H2O
CH3C(O)NHN(CH3)2 + H2O → CH3COOH + H2NN(CH3)2


UDMH is often used in hypergolic rocket fuels as a bipropellant in combination with the oxidizer nitrogen tetroxide and less frequently with IRFNA (red fuming nitric acid) or liquid oxygen. 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.[5]

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 Proton, Kosmos-3M, and the Chinese Long March 2F are the most notable users of UDMH (which is referred to as "heptyl" by Russian engineers[6]). The Titan, GSLV, and Delta rocket families use a mixture of 50% hydrazine and 50% UDMH, called Aerozine 50, in different stages.[7] There is speculation that it is the fuel used in the ballistic missiles that North Korea has developed and tested in 2017.[8]

Apart from its use as rocket fuel, UDMH is a nitrogen source in metalorganic vapor phase epitaxy thin-film deposition.[citation needed] UDMH is a contaminant, metabolite, and breakdown product of daminozide.[citation needed]


Hydrazines and its methyl derivatives are toxic but LD50 values have not been reported.(This part needs edit with data provided by reference)[9] Hydrazines are classified as carcinogens.[10]

See alsoEdit


  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 and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. ^ 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.
  5. ^ MIL-PRF-25604 (1997-10-01). "Performance Specification, Propellant, uns-Dimethylhydrazine". Retrieved 2011-05-21.
  6. ^ "Following Russian rocket explosion, experts warn of 'major contamination'".
  7. ^ Clark, John D. (1972). Ignition! An Informal History of Liquid Rocket Propellants. Rutgers University Press. p. 45. ISBN 0-8135-0725-1.
  8. ^ Broad, William J.; Sanger, David E. (17 September 2017). "The Rare, Potent Fuel Powering North Korea's Weapons" – via
  9. ^
  10. ^ Gangadhar Choudhary, Hugh Hansen (1998). "Human health perspective of environmental exposure to hydrazines: A review". Chemosphere. 37: 801–843. doi:10.1016/S0045-6535(98)00088-5.

External linksEdit