Unsymmetrical dimethylhydrazine

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Unsymmetrical dimethylhydrazine
Skeletal formula of unsymmetrical dimethylhydrazine with some implicit hydrogens shown 1,1-Dimethylhydrazin2.svg
Skeletal formula of unsymmetrical dimethylhydrazine with some implicit hydrogens shown
Ball and stick model of unsymmetrical dimethylhydrazine 1,1-dimethylhydrazine-3D-balls.png
Ball and stick model of unsymmetrical dimethylhydrazine
Names
Preferred IUPAC name
1,1-Dimethylhydrazine [1]
Other names
Dimazine
1,1-Dimethyldiazane
Identifiers
3D model (JSmol)
605261
ChEBI
ChemSpider
ECHA InfoCard 100.000.287 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 200-316-0
KEGG
MeSH dimazine
PubChem CID
RTECS number
  • MV2450000
UNII
UN number 1163
  • InChI=1S/C2H8N2/c1-4(2)3/h3H2,1-2H3 X mark.svgN
    Key: RHUYHJGZWVXEHW-UHFFFAOYSA-N X mark.svgN
  • CN(C)N
Properties
H2NN(CH3)2
AppearanceColorless liquid
Odor Ammoniacal, fishy
Density 791 kgm−3 (at 22 °C)
Melting point −57 °C; −71 °F; 216 K
Boiling point 64.0 °C; 147.1 °F; 337.1 K
Miscible [2]
Vapor pressure 13.7 kPa (at 20 °C)
1.4075
Thermochemistry
164.05 JK−1mol−1
Std molar
entropy
(S298)
200.25 JK−1mol−1
48.3 kJmol−1
−1982.3 – −1975.1 kJmol−1
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Carcinogen, spontaneously ignites on contact with oxidizers
GHS labelling:
GHS-pictogram-flamme.svg GHS-pictogram-acid.svg GHS-pictogram-skull.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H225, H301, H314, H331, H350, H411
P210, P261, P273, P280, P301+P310
NFPA 704 (fire diamond)
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 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. gasolineInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
4
3
1
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]
NIOSH (US health exposure limits):
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).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Unsymmetrical dimethylhydrazine (abbreviated as UDMH; also known as 1,1-dimethylhydrazine, heptyl or Geptil) is a chemical compound with the formula H2NN(CH3)2 that is primarily used as a rocket propellant. [4] At room temperature, UDMH is a colorless liquid, with a sharp, fishy, ammonia-like smell typical of organic amines. Samples turn yellowish on exposure to air and absorb oxygen and carbon dioxide. It is miscible with water, ethanol, and kerosene. At concentrations between 2.5% and 95% in air, its vapors are flammable. It is not sensitive to shock.

Symmetrical dimethylhydrazine (1,2-dimethylhydrazine) also exists, but it is not as useful. [5] UDMH can be oxidized in air to form many different substances, including toxic ones. [6] [7] [8]

Synthesis

In 1875, UDMH was first prepared by Emil Fischer, who discovered and named the class of hydrazines, by reducing N-Nitrosodimethylamine with zinc in boiling acetic acid. [9] [10] Fischer's student Edward Renouf later studied UDMH more extensively as part of his doctoral dissertation. Other historical lab routes include methylation of hydrazine, reduction of nitrodimethylamine and amination of dimethylamine with aminopersulfuric acid. [11]

UDMH is produced industrially by two routes. [5] Based on the Olin Raschig process, one method involves reaction of monochloramine with dimethylamine giving 1,1-dimethylhydrazinium chloride:

(CH3)2NH + NH2Cl → (CH3)2NNH2 ⋅ HCl

In the presence of suitable catalysts, acetylhydrazine can be N-dimethylated using formaldehyde and hydrogen to give the N,N-dimethyl-N'-acetylhydrazine, which can subsequently be hydrolyzed:

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

Uses

UDMH is often used in hypergolic rocket fuels as a bipropellant in combination with the oxidizer nitrogen tetroxide and less frequently with IRFNA (inhibited red fuming nitric acid) or liquid oxygen. [12] 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. [13]

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 SS-11 Sego (aka 8K84) ICBM, SS-19 Stiletto (aka 15A30) ICBM, Proton, Kosmos-3M, R-29RMU2 Layner, R-36M, Rokot (based on 15A30) and the Chinese Long March 2 are the most notable users of UDMH (which is referred to as "heptyl" (codename from Soviet era)[ citation needed ] by Russian engineers [14] ). The Titan, GSLV, and Delta rocket families use a mixture of 50% hydrazine and 50% UDMH, called Aerozine 50, in different stages. [15] There is speculation that it is the fuel used in the ballistic missiles that North Korea has developed and tested in 2017. [16]

Safety

Hydrazine and its methyl derivatives are toxic but LD50 values have not been reported. [17] It is a precursor to dimethylnitrosamine, which is carcinogenic. [18] According to scientific data, usage of UDMH in rockets at Baikonur Cosmodrome has had adverse effects on the environment. [19] One such instance was the Nedelin catastrophe in 1960 when UDMH and dinitrogen tetroxide leaked from a rocket after an explosion and killed a number of bystanders through burn injuries and its toxicity.

See also

Related Research Articles

<span class="mw-page-title-main">Titan (rocket family)</span> Family of launch vehicles used in U.S. Air Force and space programs (1959–2005)

Titan was a family of United States expendable rockets used between 1959 and 2005. The Titan I and Titan II were part of the US Air Force's intercontinental ballistic missile (ICBM) fleet until 1987. The space launch vehicle versions contributed the majority of the 368 Titan launches, including all the Project Gemini crewed flights of the mid-1960s. Titan vehicles were also used to lift US military payloads as well as civilian agency reconnaissance satellites and to send interplanetary scientific probes throughout the Solar System.

<span class="mw-page-title-main">Hydrazine</span> Colorless flammable liquid with an ammonia-like odor

Hydrazine is an inorganic compound with the chemical formula N2H4. It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydrazine hydrate.

<span class="mw-page-title-main">Hypergolic propellant</span> Type of rocket engine fuel

A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other.

A propellant is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the engine that expels the propellant is called a reaction engine. Although technically a propellant is the reaction mass used to create thrust, the term "propellant" is often used to describe a substance which contains both the reaction mass and the fuel that holds the energy used to accelerate the reaction mass. For example, the term "propellant" is often used in chemical rocket design to describe a combined fuel/propellant, although the propellants should not be confused with the fuel that is used by an engine to produce the energy that expels the propellant. Even though the byproducts of substances used as fuel are also often used as a reaction mass to create the thrust, such as with a chemical rocket engine, propellant and fuel are two distinct concepts.

Monomethylhydrazine (MMH) is a highly toxic, volatile hydrazine derivative with the chemical formula CH6N2. It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as nitrogen tetroxide and nitric acid. As a propellant, it is described in specification MIL-PRF-27404.

<span class="mw-page-title-main">RP-1</span> Highly refined form of kerosene used as rocket fuel

RP-1 (alternatively, Rocket Propellant-1 or Refined Petroleum-1) is a highly refined form of kerosene outwardly similar to jet fuel, used as rocket fuel. RP-1 provides a lower specific impulse than liquid hydrogen (H2), but is cheaper, is stable at room temperature, and presents a lower explosion hazard. RP-1 is far denser than H2, giving it a higher energy density (though its specific energy is lower). RP-1 also has a fraction of the toxicity and carcinogenic hazards of hydrazine, another room-temperature liquid fuel.

<span class="mw-page-title-main">Liquid-propellant rocket</span> Rocket engine that uses liquid fuels and oxidizers

A liquid-propellant rocket or liquid rocket uses a rocket engine burning liquid propellants. (Alternate approaches use gaseous or solid propellants.) Liquids are desirable propellants because they have reasonably high density and their combustion products have high specific impulse (Isp). This allows the volume of the propellant tanks to be relatively low.

Aerozine 50 is a 50:50 mix by weight of hydrazine and unsymmetrical dimethylhydrazine (UDMH), developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II ICBM rocket engines. Aerozine continues in wide use as a rocket fuel, typically with dinitrogen tetroxide as the oxidizer, with which it is hypergolic. Aerozine 50 is more stable than hydrazine alone, and has a higher density and boiling point than UDMH alone.

The highest specific impulse chemical rockets use liquid propellants. They can consist of a single chemical or a mix of two chemicals, called bipropellants. Bipropellants can further be divided into two categories; hypergolic propellants, which ignite when the fuel and oxidizer make contact, and non-hypergolic propellants which require an ignition source.

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<span class="mw-page-title-main">Dimethylamine</span> Chemical compound

Dimethylamine is an organic compound with the formula (CH3)2NH. This secondary amine is a colorless, flammable gas with an ammonia-like odor. Dimethylamine is commonly encountered commercially as a solution in water at concentrations up to around 40%. An estimated 270,000 tons were produced in 2005.

UH 25 is a fuel mixture for rockets. It was developed for the European Ariane 2–4 launch vehicles.

<span class="mw-page-title-main">Hydrazines</span> Class of chemical compounds

Hydrazines (R2N−NR2) are a class of chemical compounds with two nitrogen atoms linked via a covalent bond and which carry from one up to four alkyl or aryl substituents. Hydrazines can be considered as derivatives of the inorganic hydrazine (H2N−NH2), in which one or more hydrogen atoms have been replaced by hydrocarbon groups.

Tonka is the name given to a German-designed rocket propellant first used in the Wasserfall missile, and recently used by North Korea. It was used in the Soviet Union under the name TG-02, for example in the engine designs of the A.M. Isayev Chemical Engineering Design Bureau.

Devil's venom was a nickname coined by Soviet rocket scientists for a hypergolic liquid rocket fuel composed of a dangerous combination of red fuming nitric acid (RFNA) and unsymmetrical dimethylhydrazine (UDMH). Both propellants are extremely dangerous individually: nitric acid is highly corrosive and releases toxic nitrogen dioxide during reactions, or even simply while exposed to air in its highly concentrated "red fuming" form, typically used as rocket propellant. UDMH is both toxic and corrosive.

RD-270 (Russian: Раке́тный дви́гатель 270, Rocket Engine 270, 8D420) was a single-chamber liquid-bipropellant rocket engine designed by Energomash (USSR) in 1960–1970. It was to be used on the first stages of proposed heavy-lift UR-700 and UR-900 rocket families, as well as on the N1. It has the highest thrust among single-chamber engines of the USSR, 640 metric tons at the surface of Earth. The propellants used are unsymmetrical dimethylhydrazine (UDMH) and nitrogen tetroxide (N2O4). The chamber pressure was among the highest considered, being about 26 MPa. This was achieved by applying full-flow staged combustion cycle for all the incoming mass of fuel, which is turned into a gas and passes through multiple turbines before being burned in the combustion chamber. This allowed the engine to achieve a specific impulse of 301 s (2.95 km/s) at the Earth's surface.

Hydyne is a mixture of 60% unsymmetrical dimethylhydrazine (UDMH) and 40% diethylenetriamine (DETA), developed in 1957 at Rocketdyne for use in liquid-fuel rockets. Hydyne was used as the fuel for the first stage of the Juno I rocket that launched Explorer 1, the first successful satellite launch conducted by the United States. As part of Mixed Amine Fuel series of rocket fuels, it was designated as MAF-4.

<span class="mw-page-title-main">Aerojet LR87</span> American rocket engine family used on Titan missile first stages

The LR87 was an American liquid-propellant rocket engine used on the first stages of Titan intercontinental ballistic missiles and launch vehicles. Composed of twin motors with separate combustion chambers and turbopump machinery, it is considered a single unit and was never flown as a single combustion chamber engine or designed for this. The LR87 first flew in 1959.

<span class="mw-page-title-main">Symmetrical dimethylhydrazine</span> Chemical compound

Symmetrical dimethylhydrazine (SDMH), or 1,2-dimethylhydrazine, is the organic compound with the formula (CH3NH)2. It is one of the two isomers of dimethylhydrazine. Both isomers are colorless liquids at room temperature, with properties similar to those of methylamines. Symmetrical dimethylhydrazine is a potent carcinogen that acts as a DNA methylating agent. The compound has no commercial value, in contrast to its isomer unsymmetrical dimethylhydrazine (1,1-dimethylhydrazine, UDMH), which is used as a rocket fuel. Symmetrical dimethylhydrazine is more toxic than unsymmetrical dimethylhydrazine and is therefore an unwanted impurity in UDMH.

<span class="mw-page-title-main">Rocket propellant</span> Chemical or mixture used in a rocket engine

Rocket propellant is used as reaction mass ejected from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical rocket, or from an external source, as with ion engines.

References

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