Monomethylhydrazine

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Monomethylhydrazine
Skeletal formula of monomethylhydrazine with some implicit hydrogens shown
Ball and stick model of monomethylhydrazine
Identifiers
CAS number 60-34-4 YesY
PubChem 6061
ChemSpider 5837 YesY
EC number 200-471-4
UN number 1244
MeSH Monomethylhydrazine
ChEMBL CHEMBL160520 YesY
RTECS number MV5600000
Beilstein Reference 635645
Jmol-3D images Image 1
Properties
Molecular formula CH6N2
Molar mass 46.07 g mol−1
Appearance Colourless liquid
Odor fishy, ammoniacal
Density 875 mg mL−1 (at 20 °C)
Melting point −52 °C (−62 °F; 221 K)
Boiling point 91 °C; 196 °F; 364 K
log P −1.318
Vapor pressure 5.00 kPa (at 20 °C)
Refractive index (nD) 1.4325
Thermochemistry
Specific
heat capacity
C
134.93 J K−1 mol−1
Std molar
entropy
So298
165.94 J K−1 mol−1
Std enthalpy of
formation
ΔfHo298
54.14 kJ mol−1
Std enthalpy of
combustion
ΔcHo298
−1305.8–−1304.6 kJ mol−1
Hazards
MSDS inchem.org
GHS pictograms The flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The corrosion pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The health hazard pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The environment pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word DANGER
GHS hazard statements H225, H300, H311, H314, H330, H351, H411
GHS precautionary statements P210, P260, P273, P280, P284
EU classification Extremely Flammable F+ Very Toxic T+ Dangerous for the Environment (Nature) N
R-phrases R11, R24/25, R26, R34, R40, R51/53
S-phrases S16, S26, S36/37/39, S45, S60
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propane Health code 4: Very short exposure could cause death or major residual injury. E.g., VX gas Reactivity code 4: Readily capable of detonation or explosive decomposition at normal temperatures and pressures. E.g., nitroglycerin Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 20 °C (68 °F; 293 K)
Explosive limits 2.5–97%
LD50 32 mg kg−1 (oral, rat)
Related compounds
Related compounds
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Monomethylhydrazine (MMH) is a volatile hydrazine chemical with the chemical formula CH3 (NH)NH2. It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as nitrogen tetroxide (N2O4) and nitric acid (HNO3). As a propellant, it is described in specification MIL-PRF-27404.[2]

MMH is a hydrazine derivative used in the orbital maneuvering system (OMS) and reaction control system (RCS) engines of NASA's Space Shuttle, which used MMH and MON-3 (a mixture of nitrogen tetroxide with approximately 3% nitric oxide). This chemical is toxic and carcinogenic in small amounts, but it is easily stored in outer space providing moderate performance for very low fuel tank system weight. Recently the European Space Agency (ESA) has attempted to seek new options in terms of bipropellant rocket combinations to avoid poisonous chemicals such as this and its relatives.[3]

MMH and its chemical relative unsymmetrical dimethylhydrazine (UDMH) have a key advantage that they are stable enough to be used in regeneratively cooled rocket engines. The Apollo Lunar Modules used a one-to-one mixture of hydrazine and UDMH (called Aerozine 50, or A-50) as one part of the rocket fuel for lunar landings and takeoff: the rocket motors formed a hypergolic mixture of the hydrazines with liquid dinitrogen tetroxide as the usual oxidizer. (Otherwise, red fuming nitric acid works.) About three tons of mixed hydrazines and four and one half tons of the oxidizer were required for each landing, and about one-third of those amounts for the lunar take-off to orbit.[4]

Monomethylhydrazine is believed to be the main cause of the toxicity of Gyromitra genus mushrooms, especially the false morel (Gyromitra esculenta). In these cases, MMH is formed by the hydrolysis of gyromitrin.[5]

Monomethylhydrazine is considered to be a possible occupational carcinogen,[6] and the occupational exposure limits to MMH are set at protective levels to account for the possible carcinogenicity.[7]

References[edit]

  1. ^ "Monomethylhydrazine - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification and Related Records. Retrieved 2 May 2012. 
  2. ^ MIL-PRF-27404 (1997-10-01). "Performance Specification, Propellant, Monomethylhydrazine". Retrieved 2011-05-21. 
  3. ^ International Conference on Green Propellant for Space Propulsion, European Space Agency
  4. ^ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 492. ISBN 0-08-022057-6. 
  5. ^ Pyysalo H. (1975). "Some new toxic compounds in false morels, Gyromitra esculenta". Naturwissenschaften 62 (8): 395. doi:10.1007/BF00625355. PMID 1238907. 
  6. ^ Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs), Centers for Disease Control and Prevention
  7. ^ NIOSH Pocket Guide to Chemical Hazards, Centers for Disease Control and Prevention