Cyclohexanone

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 oil has an odor reminiscent of that of acetone. Over time, samples of cyclohexanone assume a yellow color. Cyclohexanone is slightly soluble in water and miscible with common organic solvents. Billions of kilograms are produced annually, mainly as a precursor to nylon.[8]

Not to be confused with Cyclexanone.
Cyclohexanone[1][2]
Skeletal formula of cyclohexanone
Ball-and-stick model of cyclohexanone
Names
Preferred IUPAC name
Cyclohexanone
Other names
oxocyclohexane, pimelic ketone, ketohexamethylene, cyclohexyl ketone, ketocyclohexane, hexanon, Hydrol-O, Sextone, K, Anone
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.003.302
KEGG
UNII
Properties
C6H10O
Molar mass 98.15 g/mol
Appearance Colorless liquid
Odor peppermint or acetone-like
Density 0.9478 g/mL, liquid
Melting point −47 °C (−53 °F; 226 K)[3]
Boiling point 155.65 °C (312.17 °F; 428.80 K)
8.6 g/100 mL (20 °C)
Solubility in all organic solvents Miscible
Vapor pressure 5 mmHg (20°C)[4]
-62.04·10−6 cm3/mol
1.447
Viscosity 2.02 cP at 25 °C[5]
Thermochemistry
+229.03 J.K−1.mol−1
Std enthalpy of
formation (ΔfH⦵298)
 −270.7 kJ mol−1
Std enthalpy of
combustion (ΔcH⦵298)
 −3519.3 kJmol−1
Hazards
GHS pictograms
GHS Signal word Danger[6]
GHS hazard statements
 H226, H302, H312, H332, H315, H318[6]
P280, P305+351+338[6]
NFPA 704 (fire diamond)
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
1
0
Flash point 44 °C (111 °F; 317 K)
420 °C (788 °F; 693 K)
Explosive limits 1.1-9.4%
Lethal dose or concentration (LD, LC):
8000 ppm (rat, 4 hr)[7]
4706 ppm (mouse, 1.5 hr)[7]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 50 ppm (200 mg/m3)[4]
REL (Recommended)
 TWA 25 ppm (100 mg/m3) [skin][4]
IDLH (Immediate danger)
 700 ppm[4]
Related compounds
Related ketones
 Cyclopentanone, cycloheptanone
Related compounds
 Cyclohexanol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references

Production

Cyclohexanone is produced by the oxidation of cyclohexane in air, typically using cobalt catalysts:[8]

C6H12 + O2 → (CH2)5CO + H2O

This process co-forms cyclohexanol, 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 intermediacy of the hydroperoxide C6H11O2H. 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.[8]

ExxonMobil developed a process in which benzene is hydroalkylated to cyclohexylbenzene. This latter product is oxidized to a hydroperoxide and then cleaved to phenol and cyclohexanone.[9] 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.[10]

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.[11]

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:[8]

Laboratory 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.[12] It forms a trimethylsilylenol ether upon treatment with trimethylsilylchloride in the presence of base.[13] It also forms an enamine with pyrolidine.[14]

Illicit use

Cyclohexanone has been used in the illicit production of phencyclidine and its analogues[15] and as such is often subject to additional checks before purchase.

Safety

Like cyclohexanol, cyclohexanone is not carcinogenic and is moderately toxic, with a TLV of 25 ppm for the vapor. It is an irritant.[8]

References
  1. International Chemical Safety Card 0425
  2. NIOSH Pocket Guide to Chemical Hazards
  3. Sigma-Aldrich - Cyclohexanone
  4. NIOSH Pocket Guide to Chemical Hazards. "#0166". National Institute for Occupational Safety and Health (NIOSH).
  5. Data extract from Landolt-Börnstein IV/25: Viscosity of Pure Organic Liquids and Binary Liquid Mixtures
  6. Sigma-Aldrich Co., Cyclohexanone. Retrieved on 2017-11-20.
  7. "Cyclohexanone". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  8. Michael T. Musser "Cyclohexanol and Cyclohexanone" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.doi:10.1002/14356007.a08_217
  9. Plotkin, Jeffrey S. (2016-03-21). "What's New in Phenol Production?". American Chemical Society. Retrieved 2019-10-27.
  10. "Phenol -- The essential chemical industry online". 2017-01-11. Retrieved 2019-10-27.
  11. "Archived copy". Archived from the original on 2012-04-26. Retrieved 2012-07-09.CS1 maint: archived copy as title (link)
  12. M. S. Newman, M. D. Farbman, H. Hipsher (1945). "2-chlorocyclohexanone". Org. Synth. 25: 22. doi:10.15227/orgsyn.025.0022.CS1 maint: uses authors parameter (link)
  13. 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.CS1 maint: uses authors parameter (link)
  14. R. B. Woodward, I. J. Pachter, M. L. Scheinbaum (1974). "2,2-(Trimethylenedithio)cyclohexanone". Org. Synth. 54: 39. doi:10.15227/orgsyn.054.0039.CS1 maint: uses authors parameter (link)
  15. 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.
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