UDMH

Unsymmetrical dimethylhydrazine

Names
IUPAC name 1,1-dimethylhydrazine
Other names Dimazine
Identifiers
CAS Number	57-14-7 Y
3D model (Jmol)	Interactive image
Beilstein Reference	605261
ChEBI	CHEBI:18853 N
ChemSpider	5756 N
ECHA InfoCard	100.000.287
EC Number	200-316-0
KEGG	C19233 Y
MeSH	dimazine
PubChem	5976
RTECS number	MV2450000
UN number	1163
InChI InChI=1S/C2H8N2/c1-4(2)3/h3H2,1-2H3 N Key: RHUYHJGZWVXEHW-UHFFFAOYSA-N N
SMILES CN(C)N
Properties
Chemical formula	C2H8N2
Molar mass	60.10 g·mol−1
Appearance	Colourless 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
Solubility in water	miscible
Vapor pressure	13.7 kPa (at 20 °C)
Refractive index (nD)	1.4075
Thermochemistry
Specific heat capacity (C)	164.05 J K−1 mol−1
Std molar entropy (So298)	200.25 J K−1 mol−1
Std enthalpy of formation (ΔfHo298)	48.3 kJ mol−1
Std enthalpy of combustion (ΔcHo298)	−1982.3–−1975.1 kJ mol−1
Hazards
Main hazards	carcinogen, spontaneously ignites on contact with oxidizers
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 classification (DSD)	F T N
R-phrases	R45, R11, R23/25, R34, R51/53
NFPA 704	3 4 1
Flash point	−10 °C (14 °F; 263 K)
Autoignition temperature	248 °C (478 °F; 521 K)
Explosive limits	2–95%
Lethal dose or concentration (LD, LC):
LD50 (median dose)	122 mg kg−1(oral, rat) 1.06 g kg−1(dermal, rabbit)
LC50 (median concentration)	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)
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 0.5 ppm (1 mg/m3) [skin]
REL (Recommended)	Ca C 0.06 ppm (0.15 mg/m3) [2-hr]
IDLH (Immediate danger)	Ca [15 ppm]
Related compounds
Related compounds	Dimethylamine hydrazine Symmetrical dimethylhydrazine
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Unsymmetrical dimethylhydrazine (UDMH; 1,1-dimethylhydrazine) is a chemical compound with the formula H₂NN(CH₃)₂. It is a colourless liquid, with a sharp, fishy, ammoniacal 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 (CH₃NHNH(CH₃)) is also known but is not as useful.

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

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

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 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). The Titan, GSLV, and Delta rocket families use a mixture of 50% hydrazine and 50% UDMH, called Aerozine 50, in different stages.