Editing Unsymmetrical dimethylhydrazine

{{short description|Rocket fuel}}
{{Use dmy dates|date=March 2024}}
{{chembox
| Verifiedfields = changed
| Watchedfields  = changed
| verifiedrevid  = 450852466
| ImageFileL1    = 1,1-Dimethylhydrazin2.svg
| ImageFileL1_Ref = {{chemboximage|correct|??}}
| ImageSizeL1    = 100
| ImageNameL1    = Skeletal formula of unsymmetrical dimethylhydrazine with some implicit hydrogens shown
| ImageFileR1    = 1,1-dimethylhydrazine-3D-balls.png
| ImageFileR1_Ref = {{chemboximage|correct|??}}
| ImageSizeR1    = 100
| ImageNameR1    = Ball and stick model of unsymmetrical dimethylhydrazine
| PIN            = 1,1-Dimethylhydrazine<ref>{{cite web|title=dimazine – Compound Summary|url=https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=5976&loc=ec_rcs|work=PubChem Compound|publisher=National Center for Biotechnology Information|access-date=21 February 2012|location=USA|date=26 March 2005|at=Identification}}</ref>
| OtherNames     = Dimazine <br />
1,1-Dimethyldiazane <br>
| Section1       = {{Chembox Identifiers
| CASNo = 57-14-7
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 4WPQ90N53J
| PubChem = 5976
| ChemSpiderID = 5756
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| EINECS = 200-316-0
| UNNumber = 1163
| KEGG = C19233
| KEGG_Ref = {{keggcite|correct|kegg}}
| MeSHName = dimazine
| ChEBI = 18853
| ChEBI_Ref = {{ebicite|correct|EBI}}
| RTECS = MV2450000
| Beilstein = 605261
| SMILES = CN(C)N
| StdInChI = 1S/C2H8N2/c1-4(2)3/h3H2,1-2H3
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = RHUYHJGZWVXEHW-UHFFFAOYSA-N
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
}}
| Section2       = {{Chembox Properties
| Formula = H<sub>2</sub>NN(CH<sub>3</sub>)<sub>2</sub>
| Appearance = Colorless liquid
| Odor = Ammoniacal, fishy
| Density = 791{{nbsp}}kg{{nnbsp}}m<sup>−3</sup> (at 22{{nbsp}}°C)
| MeltingPtK = 216
| BoilingPtK = 337.1
| VaporPressure = 13.7{{nbsp}}kPa (at 20{{nbsp}}°C)
| RefractIndex = 1.4075
| Solubility = Miscible<ref name=PGCH />
}}
| Section3       = {{Chembox Thermochemistry
| DeltaHf = 48.3{{nbsp}}kJ{{nnbsp}}mol<sup>−1</sup>
| DeltaHc = −1982.3 – −1975.1{{nbsp}}kJ{{nnbsp}}mol<sup>−1</sup>
| Entropy = 200.25{{nbsp}}J{{nnbsp}}K<sup>−1</sup>{{nnbsp}}mol<sup>−1</sup>
| HeatCapacity = 164.05{{nbsp}}J{{nnbsp}}K<sup>−1</sup>{{nnbsp}}mol<sup>−1</sup>
}}
| Section4       = {{Chembox Hazards
| GHSPictograms = {{gHS flame}} {{gHS corrosion}} {{gHS skull and crossbones}} {{gHS health hazard}} {{gHS environment}}
| GHSSignalWord = '''DANGER'''
| HPhrases = {{h-phrases|225|301|314|331|350|411}}
| PPhrases = {{p-phrases|210|261|273|280|301+310}}
| NFPA-H = 4
| NFPA-F = 3
| NFPA-R = 1
| FlashPtC = −10
| AutoignitionPtC = 248
| ExploLimits = 2–95%
| LD50 = {{unbulleted list
 | 122{{nbsp}}mg kg<sup>−1</sup> <small>(oral, rat)</small>
 | 1.06{{nbsp}}g kg<sup>−1</sup> <small>(dermal, rabbit)</small>
 }}
| PEL = TWA 0.5{{nbsp}}ppm (1{{nbsp}}mg/m<sup>3</sup>) [skin]<ref name=PGCH>{{PGCH|0227}}</ref>
| IDLH = Ca [15{{nbsp}}ppm]<ref name=PGCH />
| REL = Ca C 0.06{{nbsp}}ppm (0.15{{nbsp}}mg/m<sup>3</sup>) [2{{nbsp}}hr]<ref name=PGCH />
| MainHazards = Carcinogen, spontaneously ignites on contact with oxidizers
| LC50 = {{ubl
 | 252{{nbsp}}ppm (rat, 4{{nbsp}}hr)
 | 172{{nbsp}}ppm (mouse, 4{{nbsp}}hr)
 | 392{{nbsp}}ppm (hamster, 4{{nbsp}}hr)
 | 3580{{nbsp}}ppm (dog, 15{{nbsp}}min)
 | 1410{{nbsp}}ppm (rat, 1{{nbsp}}hr)
 | 981{{nbsp}}ppm (dog, 1{{nbsp}}hr)<ref>{{IDLH|57147|1,1-Dimethylhydrazine}}</ref>
 }}
}}
| Section5       = {{Chembox Related
| OtherCompounds = {{unbulleted list
 | [[Dimethylamine]]
 | [[Hydrazine]]
 | [[Symmetrical dimethylhydrazine]]
 }}
}}
}}

'''Unsymmetrical dimethylhydrazine''' (abbreviated as '''UDMH'''; also known as '''1,1-dimethylhydrazine''', '''heptyl''' or '''Geptil''') is a [[chemical compound]] with the formula H<sub>2</sub>NN(CH<sub>3</sub>)<sub>2</sub> that is primarily used as a [[rocket propellant]].<ref>{{Cite journal |last1=Semenkov |first1=Ivan |last2=Koroleva |first2=Tatyana |date=1 December 2022 |title=Review on the environmental impact of emissions from space launches: a case study for areas affected by the Russian space programme |url=https://doi.org/10.1007/s11356-022-23888-8 |journal=Environmental Science and Pollution Research |language=en |volume=29 |issue=60 |pages=89807–89822 |doi=10.1007/s11356-022-23888-8 |pmid=36346528 |bibcode=2022ESPR...2989807S |s2cid=253396676 |issn=1614-7499|url-access=subscription }}</ref> At room temperature, UDMH is a colorless liquid, with a sharp, fishy, ammonia-like smell typical of organic [[amine]]s. Samples turn yellowish on exposure to air and absorb [[oxygen]] and [[carbon dioxide]]. It is [[Miscibility|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.<ref name="Ullmann" /> UDMH can be oxidized in air to form many different substances, including toxic ones.<ref>{{cite journal|title=Unsymmetrical dimethylhydrazine transformation products: A review
|author=Aleksey Milyushkin, Anastasia Karnaeva
|journal=Science of the Total Environment
|volume=891
|year=2023
|page=164367
|doi=10.1016/j.scitotenv.2023.164367
|pmid=37236454
|bibcode=2023ScTEn.89164367M
|s2cid=258899003
}}</ref><ref>{{Cite journal |last1=Ul'yanovskii |first1=Nikolay V. |last2=Lakhmanov |first2=Dmitry E. |last3=Pikovskoi |first3=Ilya I. |last4=Falev |first4=Danil I. |last5=Popov |first5=Mark S. |last6=Kozhevnikov |first6=Alexander Yu. |last7=Kosyakov |first7=Dmitry S. |date=15 July 2020 |title=Migration and transformation of 1,1-dimethylhydrazine in peat bog soil of rocket stage fall site in Russian North |url=https://www.sciencedirect.com/science/article/pii/S0048969720319963 |journal=Science of the Total Environment |volume=726 |pages=138483 |doi=10.1016/j.scitotenv.2020.138483 |pmid=32315849 |bibcode=2020ScTEn.72638483U |s2cid=216073493 |issn=0048-9697|url-access=subscription }}</ref><ref>{{Cite journal |last1=Koroleva |first1=T. V. |last2=Semenkov |first2=I. N. |last3=Lednev |first3=S. A. |last4=Soldatova |first4=O. S. |date=1 February 2023 |title=Unsymmetrical Dimethylhydrazine (UDMH) and Its Transformation Products in Soils: A Review of the Sources, Detection, Behavior, Toxicity, and Remediation of Polluted Territories |url=https://doi.org/10.1134/S1064229322602001 |journal=Eurasian Soil Science |language=en |volume=56 |issue=2 |pages=210–225 |doi=10.1134/S1064229322602001 |bibcode=2023EurSS..56..210K |s2cid=257903133 |issn=1556-195X|url-access=subscription }}</ref>

== 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]].<ref name=":0">{{cite journal |author=Horst Kunz |year=2002 |title=Emil Fischer – Unequalled Classicist, Master of Organic Chemistry Research, and Inspired Trailblazer of Biological Chemistry |journal=Angewandte Chemie International Edition |volume=41 |issue=23 |pages=4439–4451 |doi=10.1002/1521-3773(20021202)41:23<4439::AID-ANIE4439>3.0.CO;2-6 |pmid=12458504}}</ref><ref>{{Cite journal |last=Fischer |first=Emil |date=July 1875 |title=Ueber die Hydrazinverbindungen der Fettreihe |url=https://books.google.com/books?id=6JdDAQAAMAAJ&pg=PA111 |journal=Berichte der deutschen chemischen Gesellschaft |language=en |volume=8 |issue=2 |pages=1587–1590 |doi=10.1002/cber.187500802203 |issn=0365-9496}}</ref> Fischer's student [[Edward Renouf (chemist)|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.<ref>{{Cite web |title=Organic Syntheses Procedure |url=https://orgsyn.org/demo.aspx?prep=CV2P0211 |access-date=2024-11-02 |website=orgsyn.org |language=en}}</ref>

UDMH is produced industrially by two routes.<ref name="Ullmann">{{Ullmann|doi=10.1002/14356007.a13_177|title= Hydrazine|year= 2001|last1= Schirmann|first1= Jean-Pierre|last2= Bourdauducq|first2= Paul|isbn= 3-527-30673-0}}</ref> Based on the [[Olin Raschig process]], one method involves reaction of [[monochloramine]] with [[dimethylamine]] giving 1,1-dimethylhydrazinium chloride:
:(CH<sub>3</sub>)<sub>2</sub>NH + NH<sub>2</sub>Cl → (CH<sub>3</sub>)<sub>2</sub>NNH<sub>2</sub> ⋅ 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:
:CH<sub>3</sub>C(O)NHNH<sub>2</sub> + 2CH<sub>2</sub>O + 2H<sub>2</sub> → CH<sub>3</sub>C(O)NHN(CH<sub>3</sub>)<sub>2</sub> + 2H<sub>2</sub>O
:CH<sub>3</sub>C(O)NHN(CH<sub>3</sub>)<sub>2</sub> + H<sub>2</sub>O → CH<sub>3</sub>COOH + H<sub>2</sub>NN(CH<sub>3</sub>)<sub>2</sub>

== Uses ==
UDMH is often used in [[hypergolic]] [[rocket fuel]]s as a [[bipropellant]] in combination with the oxidizer [[nitrogen tetroxide]] and less frequently with [[IRFNA]] (inhibited red fuming nitric acid) or [[liquid oxygen]].<ref>{{Cite journal |last1=Semenkov |first1=Ivan |last2=Koroleva |first2=Tatyana |date=1 December 2022 |title=Review on the environmental impact of emissions from space launches: a case study for areas affected by the Russian space programme |url=https://doi.org/10.1007/s11356-022-23888-8 |journal=Environmental Science and Pollution Research |language=en |volume=29 |issue=60 |pages=89807–89822 |doi=10.1007/s11356-022-23888-8 |pmid=36346528 |bibcode=2022ESPR...2989807S |s2cid=253396676 |issn=1614-7499|url-access=subscription }}</ref> 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.<ref>{{cite web|title=Performance Specification Propellant, uns-Dimethylhydrazine (MIL-PRF-25604F)|url=https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=18058|date=11 March 2014|website=ASSIST Database Quicksearch|access-date=26 May 2020}}</ref>

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 [[orbital maneuvering system|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 [[UR-100|SS-11 Sego]] (aka 8K84) ICBM, [[UR-100N|SS-19 Stiletto]] (aka 15A30) ICBM, [[Proton (rocket)|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 [[USSR|Soviet era]]){{Citation needed|date=October 2020}} by Russian engineers<ref>{{cite web|title = Following Russian rocket explosion, experts warn of 'major contamination'|date = 2 July 2013|url = https://www.theverge.com/2013/7/2/4487096/russian-rocket-explosion-proton-heptyl-contamination}}</ref>). The [[Titan (rocket family)|Titan]], [[Geosynchronous Satellite Launch Vehicle|GSLV]], and [[Delta rocket]] families use a mixture of 50% hydrazine and 50% UDMH, called [[Aerozine 50]], in different stages.<ref>{{Cite book | last = Clark | first = John D. | author-link = John Drury Clark | title = Ignition! An Informal History of Liquid Rocket Propellants | publisher = Rutgers University Press | year = 1972 | page = 45 | isbn = 0-8135-0725-1 }}</ref> There is speculation that it is the fuel used in the ballistic missiles that North Korea has developed and tested in 2017.<ref>{{cite news|url=https://www.nytimes.com/2017/09/17/world/asia/north-korea-rocket-fuel-missiles.html|title=The Rare, Potent Fuel Powering North Korea's Weapons|first1=William J.|last1=Broad|first2=David E.|last2=Sanger|newspaper=The New York Times|date=17 September 2017}}</ref>

== Safety ==
Hydrazine and its methyl derivatives are toxic but [[LD50]] values have not been reported.<ref>{{Cite web|edition=4 |url=https://www.fishersci.com/shop/msdsproxy?productName=AC116320100&productDescription=UNSYM-DIMETHYLHYDRAZINE%252C+10ML&catNo=AC116320100&vendorId=VN00032119&storeId=10652 |title=unsym-Dimethylhydrazine Safedy data |access-date=23 January 2018 |archive-date=6 July 2018 |archive-url=https://web.archive.org/web/20180706161800/https://www.fishersci.com/shop/msdsproxy?productName=AC116320100&productDescription=UNSYM-DIMETHYLHYDRAZINE%252C+10ML&catNo=AC116320100&vendorId=VN00032119&storeId=10652 |url-status=dead }}</ref> It is a precursor to [[dimethylnitrosamine]], which is carcinogenic.<ref>{{cite journal|title=Human health perspective of environmental exposure to hydrazines: A review
|author=Gangadhar Choudhary, Hugh Hansen
|journal=Chemosphere
|volume=37
|year=1998|issue=5
|pages=801–843
|doi=10.1016/S0045-6535(98)00088-5|pmid=9717244
|bibcode=1998Chmsp..37..801C
}}</ref>
According to scientific data, usage of UDMH in rockets at [[Baikonur Cosmodrome]] has had adverse effects on the environment.<ref name="ijbch.kaznu.kz">{{cite journal|url=http://ijbch.kaznu.kz/index.php/kaznu/article/view/172|title=The impact of the cosmodrome 'Baikonur' on the environment and human health|first1=P. Kh|last1=Abdrazak|first2=K. Sh|last2=Musa|date=21 June 2015|volume=8|issue=1|pages=26–29|access-date=2 August 2016|via=ijbch.kaznu.kz|journal=International Journal of Biology and Chemistry|doi=10.26577/2218-7979-2015-8-1-26-29 |archive-date=8 August 2016|archive-url=https://web.archive.org/web/20160808090550/http://ijbch.kaznu.kz/index.php/kaznu/article/view/172|url-status=live|doi-access=free}}</ref>
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 ==
* [[Aerozine 50]]
* [[C-Stoff]]
* [[Devil's venom]]
* [[UH 25]]

== References ==
{{reflist|30em}}

== Further reading ==
*{{Cite encyclopedia |title=Dimethylhydrazines |encyclopedia=Encyclopedia of Liquid Fuels |publisher=De Gruyter |last=Schmidt |first=Eckart W. |date=2022 |pages=1333–1562 |doi=10.1515/9783110750287-016 |isbn=978-3-11-075028-7 |chapter=Unsymmetrical Dimethylhydrazine}}
== External links ==
* [https://web.archive.org/web/20030207030254/http://www.astronautix.com/props/n2o4udmh.htm Encyclopedia Astronautica]
* [https://www.cdc.gov/niosh/npg/npgd0227.html CDC – NIOSH Pocket Guide to Chemical Hazards]

{{Hydrazines}}

[[Category:Hydrazines]]
[[Category:Rocket fuels]]
[[Category:Methyl compounds]]