Cyclohexanone

Cyclohexanone

Cyclohexanone

Chemical compound

Cyclohexanone is the organic compound with the formula (CH2)5CO. The molecule consists of six-carbon cyclic molecule with a ketone functional group. This colorless oily liquid[3] has a sweet odor reminiscent of benzaldehyde. Over time, samples of cyclohexanone assume a pale yellow color.[10] Cyclohexanone is slightly soluble in water and miscible with common organic solvents. Billions of kilograms are produced annually, mainly as a precursor to nylon.[11]

Not to be confused with Cyclexanone.
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Production

Cyclohexanone is produced by the oxidation of cyclohexane in air, typically using cobalt catalysts:[11]

C6H12 + O2 → (CH2)5CO + H2O

This process forms cyclohexanol as a by-product, and this mixture, called "KA Oil" for ketone-alcohol oil, is the main feedstock for the production of adipic acid. The oxidation involves radicals and the hydroperoxide C6H11O2H as an intermediate. In some cases, purified cyclohexanol, obtained by hydration of cyclohexene, is the precursor. Alternatively, cyclohexanone can be produced by the partial hydrogenation of phenol:

C6H5OH + 2 H2 → (CH2)5CO

This process can also be adjusted to favor the formation of cyclohexanol.[11]

ExxonMobil developed a process in which benzene is hydroalkylated to cyclohexylbenzene. This latter product is oxidized to a hydroperoxide and then cleaved into phenol and cyclohexanone.[12] Therefore, this newer process without producing the acetone by-product appears attractive and is similar to the cumene process as a hydroperoxide is formed and then decomposed to yield two key products.[13]

Laboratory methods

Cyclohexanone can be prepared from cyclohexanol by oxidation with chromium trioxide (Jones oxidation). An alternative method utilizes the safer and more readily available oxidant sodium hypochlorite.[14][15]

Uses

The great majority of cyclohexanone is consumed in the production of precursors to Nylon 6,6 and Nylon 6. About half of the world's supply is converted to adipic acid, one of two precursors for nylon 6,6. For this application, the KA oil (see above) is oxidized with nitric acid. The other half of the cyclohexanone supply is converted to cyclohexanone oxime. In the presence of sulfuric acid catalyst, the oxime rearranges to caprolactam, a precursor to nylon 6:[11]

Other reactions

In addition to the large scale reactions conducted in service of the polymer industry, many reactions have been developed for cyclohexanone.

In the presence of light, it undergoes alpha-chlorination to give 2-chlorocyclohexanone.[16] It forms a trimethylsilylenol ether upon treatment with trimethylsilylchloride in the presence of base.[17]

It forms an enamine with pyrrolidine.[18]

Treatment with nitrosyl chloride and ethanol in sulfur dioxide gives the oximinecarboxylic ester:[19]

(CH2)5CO + C2H5OH + NOCl → HON=CH(CH2)4CO2C2H5 + HCl

Illicit use

Cyclohexanone has been used in the illicit production of phencyclidine and its analogs[20] and is often subject to purchase restrictions, such as being listed on the Special Surveillance List in the US.[21]

Safety

Like cyclohexanol, cyclohexanone is not carcinogenic and is moderately toxic, with a TLV of 25 ppm for the vapor. It is an irritant.[11]

References

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    "ICSC 0425 – CYCLOHEXANONE". inchem.org. Retrieved 2022-08-24.
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    "CDC – NIOSH Pocket Guide to Chemical Hazards – Cyclohexanone". Centers for Disease Control and Prevention (CDC). Retrieved August 24, 2022.
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    "Cyclohexanone (CID 7967)". PubChem.
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    "Cyclohexanone". Sigma-Aldrich.
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    NIOSH Pocket Guide to Chemical Hazards. "#0166". National Institute for Occupational Safety and Health (NIOSH).
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    Ch. Wohlfarth. "Viscosity of cyclohexanone". In M.D. Lechner (ed.). Viscosity of Pure Organic Liquids and Binary Liquid Mixtures · Supplement to IV/18. Springer-Verlag. doi:10.1007/978-3-540-75486-2_192.
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    Sigma-Aldrich Co., Cyclohexanone.
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    Cyclohexanone: toxicity for animals and humans
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    "Cyclohexanone". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
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    "Cyclohexanone (CID 7967)". PubChem.
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    Musser, Michael T. (October 15, 2011). "Cyclohexanol and Cyclohexanone". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KgaA. doi:10.1002/14356007.a08_217.pub2. ISBN 978-3-527-30673-2. OCLC 46878292. Retrieved January 27, 2009.
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    Plotkin, Jeffrey S. (2016-03-21). "What's New in Phenol Production?". American Chemical Society. Archived from the original on 2019-10-27. Retrieved 2019-10-27.
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    "Phenol – The essential chemical industry online". 2017-01-11. Retrieved 2019-10-27.
  14. [14]
    "Oxidation of Cyclohexanol to Cyclohexanone". Archived from the original on 2012-04-26. Retrieved 2012-07-09.
  15. [15]
    Mohrig, Jerry R.; Nienhuis, David M.; Linck, Catherine F.; Van Zoeren, Carol; Fox, Brian G.; Mahaffy, Peter G. (June 1985). "The design of laboratory experiments in the 1980's: A case study on the oxidation of alcohols with household bleach". Journal of Chemical Education. 62 (6): 519. doi:10.1021/ed062p519.
  16. [16]
    M. S. Newman; M. D. Farbman; H. Hipsher (1945). "2-chlorocyclohexanone". Org. Synth. 25: 22. doi:10.15227/orgsyn.025.0022.
  17. [17]
    Valsamma Varghese; Manasi Saha; Kenneth M. Nicholas (1989). "Alkylations Using Hexacarbonyl(Propargylium)dicobalt Salts: 2-(1-methyl-2-propynyl)cyclohexanone". Org. Synth. 67: 141. doi:10.15227/orgsyn.067.0141.
  18. [18]
    R. B. Woodward; I. J. Pachter; M. L. Scheinbaum (1974). "2,2-(Trimethylenedithio)cyclohexanone". Org. Synth. 54: 39. doi:10.15227/orgsyn.054.0039.
  19. [19]
    Smith, Michael B.; March, Jerry (2007), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (6th ed.), New York: Wiley-Interscience, p. 1736, ISBN 978-0-471-72091-1
  20. [20]
    Shulgin, A. T.; MacLean, D. E. (25 September 2008). "Illicit Synthesis of Phencyclidine (PCP) and Several of Its Analogs". Clinical Toxicology. 9 (4): 553–560. doi:10.3109/15563657608988157. PMID 975751.
  21. [21]
    "Special Surveillance List of Chemicals, Products, Materials and Equipment Used in the Clandestine Production of Controlled Substances or Listed Chemicals". Archived from the original on April 20, 2011.
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