Unsymmetrical dimethylhydrazine

Unsymmetrical dimethylhydrazine
IUPAC name 1,1-Dimethylhydrazine
Identifiers
Abbreviations	UDMH[citation needed]
CAS number	57-14-7 Y
PubChem	5976
ChemSpider	5756 N
EC number	200-316-0
UN number	1163
KEGG	C19233 Y
MeSH	dimazine
ChEBI	CHEBI:18853 N
RTECS number	MV2450000
Beilstein Reference	605261
Jmol-3D images	Image 1
SMILES CN(C)N
InChI InChI=1S/C2H8N2/c1-4(2)3/h3H2,1-2H3 N Key: RHUYHJGZWVXEHW-UHFFFAOYSA-N N
Properties
Molecular formula	C2H8N2
Molar mass	60.1 g/mol
Appearance	Colourless, transparent liquid
Density	790 mg mL−1 (at 20 °C)
Melting point	-57 °C, 216 K, -71 °F
Boiling point	64 °C, 337.1 K, 147 °F
Vapor pressure	13.7 kPa (at 20 °C)
Refractive index (nD)	1.4075
Thermochemistry
Std enthalpy of formation ΔfHo298	48.3 kJ mol−1
Std enthalpy of combustion ΔcHo298	−1982.3–−1975.1 kJ mol−1
Standard molar entropy So298	200.25 J K−1 mol−1
Specific heat capacity, C	164.05 J K−1 mol−1
Hazards
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H225, H301, H314, H331, H350, H411
GHS precautionary statements	P210, P261, P273, P280, P301+310
EU Index	007-012-00-5
EU classification	F T N
R-phrases	R45, R11, R23/25, R34, R51/53
NFPA 704	3 4 1
Flash point	−10 °C
Autoignition temperature	248 °C
Explosive limits	2–95%
LD50	1.06 g kg−1 (dermal, rabbit) 122 mg kg−1 (oral, rat) 100 mg kg−1 (4 hour inhallation, guinea pig)
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Unsymmetrical dimethylhydrazine (UDMH) (1,1-Dimethylhydrazine) is a toxic volatile hygroscopic clear liquid, with a sharp, fishy, ammoniacal smell typical for organic amines. It turns yellowish on exposure to air and absorbs 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.

Occurrence

UDMH is a contaminant, metabolite, and breakdown product of daminozide.

Uses

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.

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 high density and 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 and Kosmos-3M are the most notable users of UDMH. The Titan, GSLV, and Delta rocket families use a mixture of 50% hydrazine and 50% UDMH, called Aerozine 50, in different stages.

Apart from its use as rocket fuel, UDMH is a nitrogen source in metalorganic vapour phase epitaxy thin-film deposition.

Safety

UDMH is toxic, a carcinogen and can explode in the presence of oxidisers. It can be absorbed through skin. During the 1980s there was concern about the levels of UDMH in various foods being a cancer risk, especially for apple juice.

See also

• C-Stoff
• Aerozine 50

External links

• http://www.astronautix.com/props/n2o4udmh.htm
• http://www.lr.tudelft.nl/live/pagina.jsp?id=e2984c9b-4864-46e0-992f-13ce92f3580b&lang=en