{{Short description|Chemical compound}} {{distinguish|azene}} {{about|the hydrazine derivatives|the use of "azine" in the names of heterocyclic compounds|Azine (heterocycle)}}

thumb|right|The generic formula of an azine. For an aldazine, R<sup>2</sup>,&nbsp;R<sup>4</sup>&nbsp;= H. '''Azines''' are a functional class of organic compounds with the connectivity {{chem2|RR′C\dN\sN\dCRR′}}. These compounds are the product of the condensation of hydrazine with ketones and aldehydes, although in practice they are often made by alternative routes. '''Ketazines''' are azines derived from ketones.<ref>{{GoldBookRef|title=ketazines|file=K03377|accessdate=2022-03-12}}</ref> For example, acetone azine is the simplest ketazine. '''Aldazines''' are azines derived from aldehydes.<ref>{{GoldBookRef|title=aldazines|file=A00207|accessdate=2022-03-12}}</ref>

==Preparation== The usual method of industrial production is the peroxide process, starting from the ketone, ammonia, and hydrogen peroxide.<ref name="Ullmann"/>

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In the laboratory, azines are typically prepared by condensation of hydrazine with two equivalents of a carbonyl.<ref name="OrgSynth">{{OrgSynth | first1 = A. C. | last1 = Day | first2 = M. C. | last2 = Whiting | title = Acetone Hydrazone | volume = 50 | pages = 3 | year = 1970 | doi= 10.15227/orgsyn.050.0003}}</ref>

Azines are also produced when chalcone reacts with a hydrazone to produce 3,5-diphenyl-1''H''-pyrazole,<ref>{{cite journal|title = Metal-free and FeCl<sub>3</sub>-catalyzed synthesis of azines and 3,5-diphenyl-1''H''-pyrazole from hydrazones and/or ketones monitored by high resolution ESI<sup>+</sup>-MS|year = 2018|journal = Indian Journal of Chemistry, Section B|volume = 57B|issue = 3|pages = 362–373|url = http://nopr.niscair.res.in/handle/123456789/43824|first1 = Jamal|last1 = Lasri|first2 = Ali I.|last2 = Ismail}}</ref> in a conversion also carried out with hydrazine hydrate.<ref>{{cite journal|title = New one step synthesis of 3,5-disubstituted pyrazoles under microwave irradiation and classical heating|year = 2008|journal = Journal of Heterocyclic Chemistry|volume = 45|issue = 2|pages = 503–505|doi = 10.1002/jhet.5570450231|first1 = Moha|last1 = Outirite|first2 = Mounim|last2 = Lebrini|first3 = Michel|last3 = Lagrenée|first4 = Fouad|last4 = Bentiss}}</ref><ref>{{cite journal|title = One-pot synthesis of 3,5-diphenyl-1''H''-pyrazoles from chalcones and hydrazine under mechanochemical ball milling|year = 2014|journal = Heterocycles|volume = 89|issue = 1|pages = 103–112|doi = 10.3987/COM-13-12867|first1 = Ze|last1 = Zhang|first2 = Ya-Jun|last2 = Tan|first3 = Chun-Shan|last3 = Wang|first4 = Hao-Hao|last4 = Wu|doi-access = free}}</ref>

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==Reactions== Azines characteristically undergo hydrolysis to hydrazines. The reaction proceeds by the intermediacy of a hydrazone: :{{chem2|R2C\dN\sN\dCR2 + H2O → R2C\dN\sNH2 + R2C\dO}} :{{chem2|R2C\dN\sNH2 + H2O → N2H4 + R2C\dO}}

Azines have been used as precursors to hydrazones:<ref name="OrgSynth"/><ref name=Ber>{{cite journal|last1=Staudinger|first1=H.|author1-link=Hermann Staudinger|last2=Gaule|first2=Alice|title=Vergleich der Stickstoff-Abspaltung bei verschiedenen aliphatischen Diazoverbindungen|journal=Berichte der Deutschen Chemischen Gesellschaft|date=July 1916|volume=49|issue=2|pages=1897–1918|doi=10.1002/cber.19160490245|url=https://zenodo.org/record/1426609}}</ref> :{{chem2|R2C\dN\sN\dCR2 + N2H4 → 2R2C\dN\sNH2}}

They are also precursors to diazo compounds.<ref>{{cite journal|last1=Day|first1=A. C.|last2=Raymond|first2=P.|last3=Southam|first3=R. M.|last4=Whiting|first4=M. C.|title=The preparation of secondary aliphatic diazo-compounds from hydrazones|journal=Journal of the Chemical Society C: Organic|date=1966|pages=467|doi=10.1039/J39660000467}}</ref><ref name="Ber"/><ref name="diazo">{{OrgSynth | first1 = S. D. | last1 = Andrews | first2 = A. C. | last2 = Day | first3 = P. | last3 = Raymond | first4 = M. C. | last4 = Whiting | title = 2-Diazopropane | collvol = 6 | collvolpages = 392 | volume = 50 | pages = 27 | year = 1970 | prep = cv6p0392}}.</ref>

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The coordination chemistry of azines (as ligands) has also been studied.<ref>{{cite journal|last1=Gudkova|first1=A. S.|last2=Reutov|first2=O. A.|last3=Aleinikova|first3=M. Ya.|title=Reactions of hydrazones and azines with metal salts|journal=Bulletin of the Academy of Sciences of the USSR Division of Chemical Science|date=August 1962|volume=11|issue=8|pages=1298–1302|doi=10.1007/BF00907973}}</ref><ref>{{cite journal|last1=Gudkova|first1=A. S.|last2=Aleinikova|first2=M. Ya.|last3=Reutov|first3=O. A.|title=Reactions of hydrazones and azines with metal salts Communication 5. Reactions of hydrazones and azines with mercuric halides|journal=Bulletin of the Academy of Sciences, USSR Division of Chemical Science|date=May 1966|volume=15|issue=5|pages=807–811|doi=10.1007/BF00849376}}</ref><ref>{{cite journal|last1=King|first1=Fiona|last2=Nicholls|first2=David|title=Complex of titanium halides with acetone azine and its isomer 3, 5, 5-trimethyl-pyrazoline|journal=Inorganica Chimica Acta|date=January 1978|volume=28|pages=55–58|doi=10.1016/S0020-1693(00)87413-7}}</ref>

Acetone is used to derivatize hydrazine into acetone azine for analysis by gas chromatography. This method is used to determine trace levels of hydrazine in drinking water<ref>{{cite journal|last1=Davis, II|first1=William E.|last2=Li|first2=Yongtao|title=Analysis of Hydrazine in Drinking Water by Isotope Dilution Gas Chromatography/Tandem Mass Spectrometry with Derivatization and Liquid−Liquid Extraction|journal=Analytical Chemistry|date=July 2008|volume=80|issue=14|pages=5449–5453|doi=10.1021/ac702536d|pmid=18564853 |bibcode=2008AnaCh..80.5449D }}</ref> and pharmaceuticals.<ref>{{cite journal|last1=Sun|first1=Mingjiang|last2=Bai|first2=Lin|last3=Liu|first3=David Q.|title=A generic approach for the determination of trace hydrazine in drug substances using in situ derivatization-headspace GC–MS|journal=Journal of Pharmaceutical and Biomedical Analysis|date=February 2009|volume=49|issue=2|pages=529–533|doi=10.1016/j.jpba.2008.11.009|pmid=19097722}}</ref>

==Applications== Ketazines are also important intermediates in the industrial production of hydrazine hydrate by the peroxide process.<ref name="Ullmann">Jean-Pierre Schirmann, Paul Bourdauducq "Hydrazine" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. {{doi|10.1002/14356007.a13_177}}.</ref> In the presence of an oxidant, ammonia and ketones react to give hydrazine via ketazine: :2 Me(Et)C=O + 2 NH<sub>3</sub> + H<sub>2</sub>O<sub>2</sub> → Me(Et)C=NN=C(Et)Me + 2 H<sub>2</sub>O The ketazine can be hydrolyzed to the hydrazine and regenerate the ketone: :Me(Et)C=NN=C(Et)Me + 2 H<sub>2</sub>O → 2 Me(Et)C=O + N<sub>2</sub>H<sub>4</sub>

Ketazines have been also used as sources of hydrazine produced ''in situ'', for example in the production of herbicide precursor 1,2,4-triazole.<ref>{{cite patent | inventor1-last = Nagata | inventor1-first = Nobuhiro | inventor2-last = Nishizawa | inventor2-first = Chiharu | inventor3-last = Kurai | inventor3-first = Toshikiyo | assign = Mitsubishi Gas Chemical Co. | title = Method of producing 1,2,4-triazole | country= US | number = 6002015 | pubdate = 1999-12-14}}.</ref>

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

==Further reading== *{{cite journal | first = E. C. | last = Gilbert | title = Studies on Hydrazine. The Hydrolysis of Dimethylketazine and the Equilibrium between Hydrazine and Acetone | journal = J. Am. Chem. Soc. | year = 1929 | volume = 51 | issue = 11 | pages = 3394–3409 | doi = 10.1021/ja01386a032 | bibcode = 1929JAChS..51.3394G }} *{{cite patent | inventor1-last = Eichenhofer | inventor1-first = Kurt-Wilhelm | inventor2-last = Schliebs | inventor2-first = Reinhard | assign = Bayer | title = Production of ketazines | country= US | number = 3965097 | pubdate = 1976-06-22}}. *{{cite patent | inventor1-first = Jean-Pierre | inventor1-last = Schirmann | inventor2-first = Jean | inventor2-last = Combroux | inventor3-first = Serge Yvon | inventor3-last = Delavarenne | assign = Produits Chimiques Ugine Kuhlmann | country= US | number = 3972878 | title = Method for preparing azines and hydrazones | pubdate = 1976-08-03}}. * {{cite patent | inventor1-first = Jean-Pierre | inventor1-last = Schirmann | inventor2-first = Pierre | inventor2-last = Tellier | inventor3-first = Henri | inventor3-last = Mathais | inventor4-first = Francis | inventor4-last = Weiss | assign = Produits Chimiques Ugine Kuhlmann | country= US | number = 3978049 | title = Process for the preparation of hydrazine compounds | pubdate = 1976-08-31}}. *{{cite patent | inventor1-first = Jean-Pierre | inventor1-last = Schirmann | inventor2-first = Jean | inventor2-last = Combroux | inventor3-first = Serge Yvon | inventor3-last = Delavarenne | assign = Produits Chimiques Ugine Kuhlmann | country = US | number = 4093656 | title = Method for making azines | pubdate = 1978-06-06}}. *{{cite patent | inventor1-first = Jean-Pierre | inventor1-last = Schirmann | inventor2-first = Jean | inventor2-last = Combroux | inventor3-first = Serge Y. | inventor3-last = Delavarenne | assign = Atochem | country = US | number = 4724133 | title = Preparation of a concentrated aqueous solution of hydrazine hydrate | pubdate = 1988-02-09}}.

Category:Functional groups Category:Azines (hydrazine derivatives)