Azine

Azines are a functional class of organic compounds with the connectivity RR'C=N-N=CRR'. These compounds are the product of the condensation of hydrazine with ketones and aldehydes, although in practice they are often made by alternative routes.

The generic formula of an azine. For an aldazine, R² = H.

Preparation

The usual method of industrial production is the peroxide process, starting from the ketone, ammonia, and hydrogen peroxide.[1]

In the laboratory, azines are typically prepared by an exothermic[2] reaction of a carbonyl compound directly with hydrazine hydrate.[3]

Azines are also produced when chalcone reacts with a hydrazone to produce 3,5-diphenyl-1H-pyrazole,[4] in a conversion also carried out with hydrazine hydrate.[5][6]

Reactions

Azines characteristically undergo hydrolysis to hydrazines.

Azines have been used as precursors to hydrazones[3][7] and diazo compounds.[8][7][9]

The coordination chemistry of azines (as ligands) has also been studied.[10][11][12] Acetone is used as a derivatize to hydrazine, through formation of acetone azine, for analysis by gas chromatography: the method has been used to determine trace levels of hydrazine in drinking water[13] and pharmaceuticals.[14]

Applications

Ketazines are also important intermediates in the industrial production of hydrazine hydrate by the peroxide process.[1] In the presence of an oxidant, ammonia and ketones react to give hydrazine via ketazine:

2 Me(Et)C=O + 2 NH₃ + H₂O₂ → Me(Et)C=NN=C(Et)Me + 2 H₂O

The ketazine can be hydrolyzed to the hydrazine and regenerate the ketone:

Me(Et)C=NN=C(Et)Me + 2 H₂O → 2 Me(Et)C=O + N₂H₄

Ketazines have been also used as sources of hydrazine produced in situ, for example in the production of herbicide precursor 1,2,4-triazole.[15]

Nomenclature

They may be further classified as aldazines or ketazines, depending on the nature of the carbonyl compound.[16][17][18][19]

Azines may also be named by substitutive or functional class nomenclature.[20][21] In functional class nomenclature, the functional modifier "azine" is appended to the name of the carbonyl compound: hence, "acetone azine".[20] In older nomenclature, the functional class name "ketazine" has been used with the names of the hydrocarbyl substituents: e.g., "methyl ethyl ketazine". In substitutive nomenclature, azines are named as derivatives of hydrazine: hence, "diisopropylidenehydrazine".[20] In the presence of groups of higher priority, the prefixes "hydrazinylidene" and "hydrazinediylidene" are used.[22]

Asymmetrical azines, that is compounds of the type X=N–N=Y with X ≠ Y, are not named as azines: in the absence of other functional groups having higher priority, they can be named as substituted hydrazones.[23]

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References

Jean-Pierre Schirmann, Paul Bourdauducq "Hydrazine" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. doi:10.1002/14356007.a13_177.
Gilbert, E. C. (1929). "Studies on Hydrazine. The Hydrolysis of Dimethylketazine and the Equilibrium between Hydrazine and Acetone". J. Am. Chem. Soc. 51 (11): 3394–3409. doi:10.1021/ja01386a032.
Day, A. C.; Whiting, M. C. (1970). "Acetone hydrazone". Organic Syntheses. 50: 3.; Collective Volume, 6, p. 10
Lasri, Jamal; Ismail, Ali I. (2018). "Metal-free and FeCl₃-catalyzed synthesis of azines and 3,5-diphenyl-1H-pyrazole from hydrazones and/or ketones monitored by high resolution ESI⁺-MS". Indian Journal of Chemistry, Section B. 57B (3): 362–373.
Outirite, Moha; Lebrini, Mounim; Lagrenée, Michel; Bentiss, Fouad (2008). "New one step synthesis of 3,5-disubstituted pyrazoles under microwave irradiation and classical heating". Journal of Heterocyclic Chemistry. 45 (2): 503–505. doi:10.1002/jhet.5570450231.
Zhang, Ze; Tan, Ya-Jun; Wang, Chun-Shan; Wu, Hao-Hao (2014). "One-pot synthesis of 3,5-diphenyl-1H-pyrazoles from chalcones and hydrazine under mechanochemical ball milling". Heterocycles. 89 (1): 103–112. doi:10.3987/COM-13-12867.
Staudinger, H.; Gaule, Alice (July 1916). "Vergleich der Stickstoff-Abspaltung bei verschiedenen aliphatischen Diazoverbindungen". Berichte der Deutschen Chemischen Gesellschaft. 49 (2): 1897–1918. doi:10.1002/cber.19160490245.
Day, A. C.; Raymond, P.; Southam, R. M.; Whiting, M. C. (1966). "The preparation of secondary aliphatic diazo-compounds from hydrazones". Journal of the Chemical Society C: Organic: 467. doi:10.1039/J39660000467.
Andrews, S. D.; Day, A. C.; Raymond, P.; Whiting, M. C. (1970). "2-Diazopropane". Organic Syntheses. 50: 27.; Collective Volume, 6, p. 392.
Gudkova, A. S.; Reutov, O. A.; Aleinikova, M. Ya. (August 1962). "Reactions of hydrazones and azines with metal salts". Bulletin of the Academy of Sciences of the USSR Division of Chemical Science. 11 (8): 1298–1302. doi:10.1007/BF00907973.
Gudkova, A. S.; Aleinikova, M. Ya.; Reutov, O. A. (May 1966). "Reactions of hydrazones and azines with metal salts Communication 5. Reactions of hydrazones and azines with mercuric halides". Bulletin of the Academy of Sciences, USSR Division of Chemical Science. 15 (5): 807–811. doi:10.1007/BF00849376.
King, Fiona; Nicholls, David (January 1978). "Complex of titanium halides with acetone azine and its isomer 3, 5, 5-trimethyl-pyrazoline". Inorganica Chimica Acta. 28: 55–58. doi:10.1016/S0020-1693(00)87413-7.
Davis, II, William E.; Li, Yongtao (July 2008). "Analysis of Hydrazine in Drinking Water by Isotope Dilution Gas Chromatography/Tandem Mass Spectrometry with Derivatization and Liquid−Liquid Extraction". Analytical Chemistry. 80 (14): 5449–5453. doi:10.1021/ac702536d. PMID 18564853.
Sun, Mingjiang; Bai, Lin; Liu, David Q. (February 2009). "A generic approach for the determination of trace hydrazine in drug substances using in situ derivatization-headspace GC–MS". Journal of Pharmaceutical and Biomedical Analysis. 49 (2): 529–533. doi:10.1016/j.jpba.2008.11.009. PMID 19097722.
US 6002015, Nagata, Nobuhiro; Chiharu Nishizawa & Toshikiyo Kurai, "Method of producing 1,2,4-triazole", issued 1999-12-14, assigned to Mitsubishi Gas Chemical Co..
Moss, G. P.; Smith, P. A. S.; Tavernier, D. (1995), "Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)", Pure Appl. Chem., 67 (8–9): 1307–75 at 1321, doi:10.1351/pac199567081307.
IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "azines". doi:10.1351/goldbook.A00557.
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IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "aldazines". doi:10.1351/goldbook.A00207. IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "ketazines". doi:10.1351/goldbook.K03377.
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