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Monomethyl hydrazine

Monomethylhydrazine
Skeletal formula of monomethylhydrazine with some implicit hydrogens shown
Ball and stick model of monomethylhydrazine
Names
IUPAC name
Methylhydrazine
Identifiers
3D model (Jmol)
635645
ChemSpider
ECHA InfoCard 100.000.429
EC Number 200-471-4
MeSH Monomethylhydrazine
PubChem CID
RTECS number MV5600000
UN number 1244
Properties
CH6N2
Molar mass 46.07 g·mol−1
Appearance Fuming, 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
miscible
log P −1.318
Vapor pressure 5.00 kPa (at 20 °C)
1.4325
Thermochemistry
134.93 J K−1 mol−1
165.94 J K−1 mol−1
54.14 kJ mol−1
−1305.8–−1304.6 kJ mol−1
Hazards
Safety data sheet 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
H225, H300, H311, H314, H330, H351, H411
P210, P260, P273, P280, P284
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 −8 °C; 17 °F; 265 K
196 °C (385 °F; 469 K)
Explosive limits 2.5–92%
Lethal dose or concentration (LD, LC):
LD50 (median dose)
 32 mg kg−1(oral, rat)
34 ppm (rat, 4 hr)
74 ppm (rat, 4 hr)
162 ppm (monkey, 1 hr)
195 ppm (dog, 30 min)
145 ppm (monkey, 30 min)
272 ppm (mouse, 30 min)
427 ppm (rat, 30 min)
56 ppm (mouse, 4 hr)
143 ppm (hamster, 4 hr)
US health exposure limits (NIOSH):
PEL (Permissible)
 C 0.2 ppm (0.35 mg/m3) [skin]
REL (Recommended)
 Ca C 0.04 ppm (0.08 mg/m3) [2-hr]
IDLH (Immediate danger)
 Ca [20 ppm]
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY  (what is YesYN ?)
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.

MMH is a hydrazine derivative that was once 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.

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.


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