Editing Hydrazine (section)

==Reactions==
===Acid-base behavior===
[[File:Sample of hydrazine hydrate.jpg|thumb|Hydrazine hydrate]]
Hydrazine forms a [[monohydrate]] {{chem2|N2H4*H2O}} that is denser (1.032 g/cm<sup>3</sup>) than the [[anhydrous]] form {{chem2|N2H4}} (1.021 g/cm<sup>3</sup>). Hydrazine has [[base (chemistry)|basic]] ([[alkali]]) chemical properties comparable to those of [[ammonia]]:<ref>{{cite book |title = Handbook of Chemistry and Physics |edition = 83rd |publisher = CRC Press |date = 2002}}</ref>
:{{chem2|N2H4 + H2O → [N2H5]+ + OH-}}, ''K''<sub>b</sub> = 1.3 × 10<sup>−6</sup>, p''K''<sub>b</sub> = 5.9

(for ammonia ''K''<sub>b</sub> = 1.78 × 10<sup>−5</sup>)

It is difficult to diprotonate:<ref>{{Cite book |title=Inorganic chemistry |vauthors=Holleman AF, Wiberg E, Wiberg N|date=2001 |publisher=Academic Press |isbn=978-0-12-352651-9 |edition=1st Eng. |location=San Diego |oclc=813400418}}</ref>
:{{chem2|[N2H5]+ + H2O → [N2H6](2+) + OH-}}, ''K''<sub>b</sub> = 8.4 × 10<sup>−16</sup>, p''K''<sub>b</sub> = 15

Exposure to extremely strong bases or alkali metals generates deprotonated hydrazide salts.  Most explode on exposure to air or moisture.<ref>{{Kirk-Othmer|title=Hydrazine and its derivatives|year=2004|author=Eugene&nbsp;F. Rothgery|doi=10.1002/0471238961.0825041819030809.a01.pub2}} </ref>

===Redox reactions===
Ideally, the combustion of hydrazine in oxygen produces nitrogen and water:
:{{chem2|N2H4 + O2 → N2 + 2 H2O}}

An excess of oxygen gives oxides of nitrogen, including [[nitrogen monoxide]] and [[nitrogen dioxide]]:
:{{chem2|N2H4 + 2 O2 → 2 NO + 2 H2O}}
:{{chem2|N2H4 + 3 O2 → 2 NO2 + 2 H2O}}

The heat of combustion of hydrazine in oxygen (air) is 19.41 MJ/kg (8345 BTU/lb).<ref>{{cite web |url=http://cameochemicals.noaa.gov/chris/HDZ.pdf |title=Hydrazine—Chemical Hazard Properties Table |date=1999 |website=NOAA.gov}}</ref>

Hydrazine is a convenient reductant because the by-products are typically nitrogen gas and water. This property makes it useful as an [[antioxidant]], an oxygen [[scavenger (chemistry)|scavenger]], and a [[corrosion inhibitor]] in water boilers and heating systems. It also directly reduces salts of less active metals (e.g., bismuth, arsenic, copper, mercury, silver, lead, platinum, and palladium) to the element.<ref>{{cite book|url=https://archive.org/details/cftri.2662nonaqueoussolven0000ludw/page/133/|page=133|title=Non-aqueous solvents|first1=Ludwig F.|last1=Audrieth|first2=Jacob|last2=Kleinberg|publisher=John Wiley & Sons|location=New York|year=1953|lccn=52-12057}}</ref>  That property has commercial application in [[electroless nickel plating|electroless]] [[nickel]] plating and [[plutonium]] extraction from [[nuclear waste|nuclear reactor waste]]. Some colour photographic processes also use a weak solution of hydrazine as a stabilising wash, as it scavenges [[dye coupler]] and unreacted silver halides. Hydrazine is the most common and effective reducing agent used to convert [[graphene oxide]] (GO) to reduced graphene oxide (rGO) via hydrothermal treatment.<ref>{{cite journal |vauthors=Stankovich S, Dikin DA, Piner RD, Kohlhaas KA, Kleinhammes A, Jia Y, Wu Y, Nguyen ST, Ruoff RS |date=2007 |title=Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide |journal=[[Carbon (journal)|Carbon]] |volume=45 |issue=7 |pages=1558–1565 |doi=10.1016/j.carbon.2007.02.034|bibcode=2007Carbo..45.1558S |s2cid=14548921 }}</ref>

===Hydrazinium salts===
Hydrazine can be [[protonated]] to form various solid salts of the [[hydrazinium]] cation {{chem2|[N2H5]+}}, by treatment with mineral acids. A common salt is [[hydrazinium hydrogensulfate]], {{chem2|[N2H5]+[HSO4]-}}.<ref>{{cite web |url=http://hazard.com/msds/mf/baker/baker/files/h3633.htm |title=HYDRAZINE SULFATE |website=hazard.com |access-date=22 Jan 2019}}</ref> Hydrazinium hydrogensulfate was investigated as a treatment of cancer-induced [[cachexia]], but proved ineffective.<ref>{{cite journal |vauthors=Gagnon B, Bruera E |date=May 1998 |title=A review of the drug treatment of cachexia associated with cancer |journal=[[Drugs (journal)|Drugs]] |volume=55 |issue=5 |pages=675–88 |doi=10.2165/00003495-199855050-00005 |pmid=9585863 |s2cid=22180434}}</ref>

Double protonation gives the hydrazinium [[dication]] or hydrazinediium, {{chem2|[N2H6](2+)}}, of which various salts are known.<ref>{{cite web |url=http://www.easychem.org/en/subst-ref/?id=3969 |title=Diazanediium |website=CharChem |access-date=22 Jan 2019}}</ref>

===Organic chemistry===
Hydrazines are part of many [[organic synthesis|organic syntheses]], often those of practical significance in [[pharmaceutical]]s (see applications section), as well as in textile [[dye]]s and in photography.<ref name=Ullmann/>

Hydrazine is used in the [[Wolff–Kishner reduction]], a reaction that transforms the [[carbonyl]] group of a [[ketone]] into a [[methylene bridge]] (or an [[aldehyde]] into a [[methyl group]]) via a [[hydrazone]] intermediate. Upon the catalysis with transition-metals, the hydrazones are used as organometallic reagent equivalents (HOME chemistry) for C-C bond formations.<ref>{{Cite journal |vauthors=Li, CJ |date=2023 |title=HOME chemistry: hydrazone as organo-metallic equivalent |journal=[[Pure Appl. Chem.]] |volume=95 |page=465-474 |doi=10.1515/pac-2022-1003|pmc=11585908 }}</ref> The production of the highly stable [[dinitrogen]] from the hydrazine derivative helps to drive the reaction.

Being bifunctional, with two amines, hydrazine is a key building block for the preparation of many heterocyclic compounds via condensation with a range of difunctional [[electrophiles]]. With [[2,4-pentanedione]], it condenses to give the [[3,5-Dimethylpyrazole|3,5-dimethylpyrazole]].<ref>{{Cite journal |vauthors=Wiley RH, Hexner PE |date=1951 |title=3,5-Dimethylpyrazole |journal=[[Organic Syntheses|Org. Synth.]] |volume=31 |page=43 |doi=10.15227/orgsyn.031.0043}}</ref> In the [[Einhorn-Brunner reaction]] hydrazines react with imides to give [[triazole]]s.

Being a good nucleophile, {{chem2|N2H4}} can attack sulfonyl halides and acyl halides.<ref>{{Cite journal |vauthors=Friedman L, Litle RL, Reichle WR |date=1960 |title=p-Toluenesulfonyl Hydrazide |journal=[[Organic Syntheses|Org. Synth.]] |volume=40 |page=93 |doi=10.15227/orgsyn.040.0093}}</ref> The [[tosyl]]hydrazine also forms hydrazones upon treatment with carbonyls.

Hydrazine is used to cleave ''N''-alkylated phthalimide derivatives. This scission reaction allows phthalimide anion to be used as amine precursor in the [[Gabriel synthesis]].<ref>{{Cite journal |vauthors=Weinshenker NM, Shen CM, Wong JY |date=1977 |title=Polymeric Carbodiimide. Preparation |journal=[[Organic Syntheses|Org. Synth.]] |volume=56 |page=95 |doi=10.15227/orgsyn.056.0095}}</ref>

====Hydrazone formation====
Illustrative of the condensation of hydrazine with a simple carbonyl is its reaction with acetone to give the [[acetone azine]]. The latter reacts further with hydrazine to yield [[acetone hydrazone]]:<ref>{{Cite journal |vauthors=Day AC, Whiting MC |date=1970 |title=Acetone Hydrazone |journal=Organic Syntheses |volume=50 |page=3 |doi=10.15227/orgsyn.050.0003}}</ref>

:{{chem2|2 (CH3)2CO + N2H4 → 2 H2O + ((CH3)2C\dN)2}}
:{{chem2|((CH3)2C\dN)2 + N2H4 → 2 (CH3)2C\dNNH2}}

The propanone azine is an intermediate in the Atofina-[[Pechiney–Ugine–Kuhlmann process|PCUK process]]. Direct [[alkylation]] of hydrazines with [[alkyl halides]] in the presence of base yields alkyl-substituted hydrazines, but the reaction is typically inefficient due to poor control on level of substitution (same as in ordinary [[amine]]s). The reduction of [[hydrazone]]s to hydrazines present a clean way to produce 1,1-dialkylated hydrazines.

In a related reaction, 2-cyanopyridines react with hydrazine to form amide hydrazides, which can be converted using [[diketone|1,2-diketones]] into [[triazine]]s.

===Biochemistry===
Hydrazine is the intermediate in the anaerobic oxidation of ammonia ([[anammox]]) process.<ref>{{cite journal |vauthors=Strous M, Jetten MS |date=2004 |title=Anaerobic Oxidation of Methane and Ammonium |journal=[[Annual Review of Microbiology|Annu Rev Microbiol]] |volume=58 |pages=99–117 |doi=10.1146/annurev.micro.58.030603.123605 |pmid=15487931|hdl=2066/60186 |hdl-access=free }}</ref> It is produced by some yeasts and the open ocean bacterium anammox (''[[Brocadia anammoxidans]]'').<ref>{{cite news |url=http://www.wildsingapore.com/news/20051112/051109-5.htm |title=Bacteria Eat Human Sewage, Produce Rocket Fuel |last=Handwerk |first=Brian |date=9 Nov 2005 |access-date=12 Nov 2007 |publisher=[[National Geographic Society|National Geographic]] |via=Wild Singapore}}</ref>

The [[false morel]] produces the poison [[gyromitrin]] which is an organic derivative of hydrazine that is converted to [[monomethylhydrazine]] by metabolic processes. Even the most popular edible "button" mushroom ''[[Agaricus bisporus]]'' produces organic hydrazine derivatives, including [[agaritine]], a [[Hydrazines|hydrazine derivative]] of an amino acid, and [[gyromitrin]].<ref>{{cite journal |vauthors=Hashida C, Hayashi K, Jie L, Haga S, Sakurai M, Shimizu H |date=1990 |title=[Quantities of agaritine in mushrooms (''Agaricus bisporus'') and the carcinogenicity of mushroom methanol extracts on the mouse bladder epithelium] |journal=Nippon Koshu Eisei Zasshi |language=ja |volume=37 |issue=6 |pages=400–5 |pmid=2132000}}</ref><ref>{{cite web |url=http://www.psms.org/sporeprints/sp338.html |title=Spore Prints #338 |veditors=Sieger AA |date=1 Jan 1998 |work=Bulletin of the Puget Sound Mycological Society |access-date=13 Oct 2008}}</ref>