Unsymmetrical dimethylhydrazine

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. 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.

UDMH is produced industrially by two routes. 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. 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.

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) 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. There is speculation that it is the fuel used in the ballistic missiles that North Korea has developed and tested in 2017.

Safety

Hydrazine and its methyl derivatives are toxic but LD50 values have not been reported. It is a precursor (via oxidation) to dimethylnitrosamine, which is carcinogenic.{{cite journal|title=Human health perspective of environmental exposure to hydrazines: A review According to scientific data, usage of UDMH in rockets at Baikonur Cosmodrome has had adverse effects on the environment. 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.

References

References

1. (26 March 2005). "dimazine – Compound Summary". National Center for Biotechnology Information.
2. {{PGCH. 0227
3. {{IDLH. 57147. 1,1-Dimethylhydrazine
4. (1 December 2022). "Review on the environmental impact of emissions from space launches: a case study for areas affected by the Russian space programme". Environmental Science and Pollution Research.
5. (15 July 2020). "Migration and transformation of 1,1-dimethylhydrazine in peat bog soil of rocket stage fall site in Russian North". Science of the Total Environment.
6. (1 February 2023). "Unsymmetrical Dimethylhydrazine (UDMH) and Its Transformation Products in Soils: A Review of the Sources, Detection, Behavior, Toxicity, and Remediation of Polluted Territories". Eurasian Soil Science.
7. Horst Kunz. (2002). "Emil Fischer – Unequalled Classicist, Master of Organic Chemistry Research, and Inspired Trailblazer of Biological Chemistry". Angewandte Chemie International Edition.
8. Fischer, Emil. (July 1875). "Ueber die Hydrazinverbindungen der Fettreihe". Berichte der Deutschen Chemischen Gesellschaft.
9. "Organic Syntheses Procedure".
10. (2001). "Hydrazine".
11. (1 December 2022). "Review on the environmental impact of emissions from space launches: a case study for areas affected by the Russian space programme". Environmental Science and Pollution Research.
12. (11 March 2014). "Performance Specification Propellant, uns-Dimethylhydrazine (MIL-PRF-25604F)".
13. (2 July 2013). "Following Russian rocket explosion, experts warn of 'major contamination'".
14. Clark, John D.. (1972). "Ignition! An Informal History of Liquid Rocket Propellants". Rutgers University Press.
15. (17 September 2017). "The Rare, Potent Fuel Powering North Korea's Weapons". The New York Times.
16. "unsym-Dimethylhydrazine Safedy data".
17. (21 June 2015). "The impact of the cosmodrome 'Baikonur' on the environment and human health". International Journal of Biology and Chemistry.