Difference between revisions of "Acetone azine"

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The industrial preparation of acetone azine<ref name="PCUK"/> might, at first sight, appear to be the reverse of the laboratory procedure: the azine is produced from [[acetone hydrazone]], and then [[Hydrolysis|hydrolyzed]] to give [[hydrazine hydrate]] and [[acetone]]. The interest in preparing the azine is that it can be removed from the initial reaction mixture as an [[azeotrope]] with water:<ref name="Atochem"/> in both laboratory practice and the Atofina–PCUK process, the aim is to avoid directly handling the unstable acetone hydrazone.
 
The industrial preparation of acetone azine<ref name="PCUK"/> might, at first sight, appear to be the reverse of the laboratory procedure: the azine is produced from [[acetone hydrazone]], and then [[Hydrolysis|hydrolyzed]] to give [[hydrazine hydrate]] and [[acetone]]. The interest in preparing the azine is that it can be removed from the initial reaction mixture as an [[azeotrope]] with water:<ref name="Atochem"/> in both laboratory practice and the Atofina–PCUK process, the aim is to avoid directly handling the unstable acetone hydrazone.
  
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The Atofina–PCUK process produces acetone azine from acetone (2&nbsp;eq.), [[ammonia]] (2&nbsp;eq.) and [[hydrogen peroxide]] (1&nbsp;eq.). The first step is the formation of [[acetone imine]], Me<sub>2</sub>C=NH; this is then oxidized by hydrogen peroxide through a complex mechanism to give [[3,3-dimethyloxaziridine]], which reacts with a further molecule of ammonia to produce acetone hydrazone. The hydrazone then [[Condensation reaction|condenses]] with a further molecule of acetone to produce the azine. The acetone azine product is distilled out of the reaction mixture as its azeotrope with water (''n''(H<sub>2</sub>O)/''n''(azine)&nbsp;= 6).<ref name="Atochem"/>
+
The original Atofina–PCUK process produces acetone azine from acetone (2&nbsp;eq.), [[ammonia]] (2&nbsp;eq.) and [[hydrogen peroxide]] (1&nbsp;eq.). The first step is the formation of [[acetone imine]], Me<sub>2</sub>C=NH; this is then oxidized by hydrogen peroxide through a complex mechanism to give [[3,3-dimethyloxaziridine]], which reacts with a further molecule of ammonia to produce acetone hydrazone. The hydrazone then [[Condensation reaction|condenses]] with a further molecule of acetone to produce the azine. The acetone azine product is distilled out of the reaction mixture as its azeotrope with water (''n''(H<sub>2</sub>O)/''n''(azine)&nbsp;= 6).<ref name="Atochem"/> Later developments of the process replace the acetone with [[butanone]] (methyl ethyl ketone): the basic chemistry remains the same, but the [[butanone azine]] is immiscible in the reaction mixture, and can be separated by decantation.<ref>{{citation | title = Synthetic nitrogen products: a practical guide to the products and processes | first = Gary R. | last = Maxwell | pages = 342–43 | publisher = Springer | year = 2004 | isbn = 0306482258}}.</ref> A similar process based on the production of [[benzophenone azine]] from [[benzophenone]] has also been described,<ref>{{citation | title = Hydrazine Production from Ammonia via Azine | first1 = Hiromu | last1 = Hayashi | first2 = Akihiko | last2 = Kainoh | first3 = Masayoshi | last3 = Katayama | first4 = Kengo | last4 = Kawasaki | first5 = Tatsuya | last5 = Okazaki | journal = Ind. Eng. Chem. Prod. Res. Dev. | year = 1976 | volume = 15 | issue = 4 | pages = 299–303 | doi = 10.1021/i360060a016}}.</ref> but never industrially implemented.
  
 
The [[hydrolysis]] of the azine is [[Acid catalysis|acid-catalyzed]], hence the need to isolate the azine from the initial ammonia-containing reaction mixture. It is also [[endothermic]],<ref>{{citation | first = E. C. | last = Gilbert | journal = J. Am. Chem. Soc. | year = 1929 | volume = 51 | pages = 3394–3409}}.</ref> and so requires an increase in temperature (and pressure) to shift the equilibrium in favour of the desired products: acetone (which is recycled) and hydrazine hydrate.<ref name="Atochem"/> The reaction is carried out by simple [[distillation]] of the azeotrope: typical conditions are a pressure of 8&nbsp;bar and temperatures of 130&nbsp;°C at the base of the column and 179&nbsp;°C at the top of the column. The hydrazine hydrate (30–45% aqueous solution) is run off from the base of the column, while the acetone is distilled off from the top of the column and recycled.<ref name="Atochem"/>
 
The [[hydrolysis]] of the azine is [[Acid catalysis|acid-catalyzed]], hence the need to isolate the azine from the initial ammonia-containing reaction mixture. It is also [[endothermic]],<ref>{{citation | first = E. C. | last = Gilbert | journal = J. Am. Chem. Soc. | year = 1929 | volume = 51 | pages = 3394–3409}}.</ref> and so requires an increase in temperature (and pressure) to shift the equilibrium in favour of the desired products: acetone (which is recycled) and hydrazine hydrate.<ref name="Atochem"/> The reaction is carried out by simple [[distillation]] of the azeotrope: typical conditions are a pressure of 8&nbsp;bar and temperatures of 130&nbsp;°C at the base of the column and 179&nbsp;°C at the top of the column. The hydrazine hydrate (30–45% aqueous solution) is run off from the base of the column, while the acetone is distilled off from the top of the column and recycled.<ref name="Atochem"/>

Revision as of 10:40, 29 June 2010

Acetone azine
IUPAC name acetone azine
diisopropylidenehydrazine
Identifiers
InChI InChI=1/C6H12N2/c1-5(2)7-8-6(3)4/h1-4H3
InChIKey PFLUPZGCTVGDLV-UHFFFAOYAR
Standard InChI InChI=1S/C6H12N2/c1-5(2)7-8-6(3)4/h1-4H3
Standard InChIKey PFLUPZGCTVGDLV-UHFFFAOYSA-N
CAS number [627-70-3]
EC number 211-009-6
ChemSpider 71417
SMILES
Properties[1]
Chemical formula C6H12N2
Molar mass 112.17 g mol−1
Appearance colourless liquid
Density 0.8390 g cm−3
Melting point

−12.5 °C

Boiling point

133 °C

Refractive index (nD) 1.4535
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Acetone azine, Me2C=N–N=CMe2, is the condensation product of two equivalents of acetone with one equivalent of hydrazine. It is an intermediate in the industrial production of hydrazine by the Atofina–PCUK process[2][3] and by the Bayer hydrazine process.[4]

Laboratory preparation and use

On a laboratory scale, acetone azine is prepared by the direct reaction of acetone with hydrazine hydrate, with water being removed from the product by stirring with solid potassium hydroxide:[5][6] it is also commercially available. It is a useful precursor to acetone hydrazone[6][7] and hence to 2-diazopropane,[7][8][9] both of which must be prepared immediately before use and cannot be stored.[6][9]

As well as its use as an intermediate in organic synthesis, the coordination chemistry of acetone azine (as a ligand) has also been studied.[10][11]

Production of hydrazine

Atofina–PCUK process

The industrial preparation of acetone azine[2] might, at first sight, appear to be the reverse of the laboratory procedure: the azine is produced from acetone hydrazone, and then hydrolyzed to give hydrazine hydrate and acetone. The interest in preparing the azine is that it can be removed from the initial reaction mixture as an azeotrope with water:[3] in both laboratory practice and the Atofina–PCUK process, the aim is to avoid directly handling the unstable acetone hydrazone.

The original Atofina–PCUK process produces acetone azine from acetone (2 eq.), ammonia (2 eq.) and hydrogen peroxide (1 eq.). The first step is the formation of acetone imine, Me2C=NH; this is then oxidized by hydrogen peroxide through a complex mechanism to give 3,3-dimethyloxaziridine, which reacts with a further molecule of ammonia to produce acetone hydrazone. The hydrazone then condenses with a further molecule of acetone to produce the azine. The acetone azine product is distilled out of the reaction mixture as its azeotrope with water (n(H2O)/n(azine) = 6).[3] Later developments of the process replace the acetone with butanone (methyl ethyl ketone): the basic chemistry remains the same, but the butanone azine is immiscible in the reaction mixture, and can be separated by decantation.[12] A similar process based on the production of benzophenone azine from benzophenone has also been described,[13] but never industrially implemented.

The hydrolysis of the azine is acid-catalyzed, hence the need to isolate the azine from the initial ammonia-containing reaction mixture. It is also endothermic,[14] and so requires an increase in temperature (and pressure) to shift the equilibrium in favour of the desired products: acetone (which is recycled) and hydrazine hydrate.[3] The reaction is carried out by simple distillation of the azeotrope: typical conditions are a pressure of 8 bar and temperatures of 130 °C at the base of the column and 179 °C at the top of the column. The hydrazine hydrate (30–45% aqueous solution) is run off from the base of the column, while the acetone is distilled off from the top of the column and recycled.[3]

Bayer hydrazine process

The Bayer hydrazine process is a modification of the Raschig/Olin process, that is the oxidation of ammonia with sodium hypochlorite to produce hydrazine. The addition of acetone to the reaction mixture allows the separation and purification of acetone azine before its hydrolysis to hydrazine hydrate.[4]

References

  1. ↑ CRC Handbook of Chemistry and Physics, 62nd ed.; Weast, Robert C., Ed.; CRC Press: Boca Raton, FL, 1981; p C-74. ISBN 0-8493-0462-8.
  2. ↑ 2.0 2.1 Schirmann, Jean-Pierre; Combroux, Jean; Delavarenne, Serge Yvon (Produits Chimiques Ugine Kuhlmann) Method for preparing azines and hydrazones. US Patent 3972878, issued 3 August 1976. Schirmann, Jean-Pierre; Tellier, Pierre; Mathais, Henri, et al. (Produits Chimiques Ugine Kuhlmann) Process for the preparation of hydrazine compounds. US Patent 3978049, issued 31 August 1976.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Schirmann, Jean-Pierre; Combroux, Jean; Delavarenne, Serge Y. (Atochem) Preparation of a concentrated aqueous solution of hydrazine hydrate. US Patent 4724133, issued 9 February 1988.
  4. ↑ 4.0 4.1 Holleman, A. F.; Wiberg, E. Inorganic Chemistry; Academic Press: San Diego, 2001; p 619. ISBN 0-12-352651-5.
  5. ↑ Curtius, T.; Thun, K. J. Prakt. Chem. 1891, 44, 161.
  6. ↑ 6.0 6.1 6.2 Day, A. C.; Whiting, M. C. Acetone hydrazone. Org. Synth. 1970, 50, 3, <http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6p0010>; Coll. Vol., 6, 10.
  7. ↑ 7.0 7.1 Staudinger, H.; Gaule, A. Ber. Dtsch. Chem. Ges. 1916, 49, 1897.
  8. ↑ Day, A. C.; Raymond, P.; Southam, R. M.; Whiting, M. C. J. Chem. Soc. C 1966, 467.
  9. ↑ 9.0 9.1 Andrews, S. D.; Day, A. C.; Raymond, P.; Whiting, M. C. 2-Diazopropane. Org. Synth. 1970, 50, 27, <http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6p0392>; Coll. Vol., 6, 392.
  10. ↑ Gudkova, A. S.; Reutov, O. A.; Aleinikova, M. Ya. Izv. Akad. Nauk SSSR, Otdel. Khim. Nauk 1962 (8), 1382–87; Reactions of hydrazones and azines with metal salts 4. Reactions of azines of aldehydes and ketones with cupric salts. Russ. Chem. Bull. (Transl.) 1962, 11 (8), 1298–1302. DOI: 10.1007/BF00907973.
  11. ↑ King, Fiona; Nicholls, David Complex of titanium halides with acetone azine and its isomer 3,5,5-trimethyl-pyrazoline. Inorg. Chim. Acta 1978, 28, 55–58. DOI: 10.1016/S0020-1693(00)87413-7.
  12. ↑ Maxwell, Gary R. Synthetic nitrogen products: a practical guide to the products and processes; Springer, 2004; pp 342–43. ISBN 0306482258.
  13. ↑ Hayashi, Hiromu; Kainoh, Akihiko; Katayama, Masayoshi; Kawasaki, Kengo; Okazaki, Tatsuya Hydrazine Production from Ammonia via Azine. Ind. Eng. Chem. Prod. Res. Dev. 1976, 15 (4), 299–303. DOI: 10.1021/i360060a016.
  14. ↑ Gilbert, E. C. J. Am. Chem. Soc. 1929, 51, 3394–3409.
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