Cyclohexanone is the
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
with the
formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...
(CH
2)
5CO. The molecule consists of six-carbon
cyclic molecule
A cyclic compound (or ring compound) is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where a ...
with a
ketone functional
group. This colorless oily liquid
has an odor reminiscent of
acetone
Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour.
Acetone is miscibl ...
. Over time, samples of cyclohexanone assume a pale 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
Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic.
Nylon is a silk-like thermoplastic, generally made from pet ...
.
Production
Cyclohexanone is produced by the oxidation of
cyclohexane in air, typically using cobalt catalysts:
[
:C6H12 + O2 → (CH2)5CO + H2O
This process forms ]cyclohexanol
Cyclohexanol is the organic compound with the formula HOCH(CH2)5. The molecule is related to cyclohexane by replacement of one hydrogen atom by a hydroxyl group. This compound exists as a deliquescent colorless solid with a camphor-like odor, ...
as a by-product
A by-product or byproduct is a secondary product derived from a production process, manufacturing process or chemical reaction; it is not the primary product or service being produced.
A by-product can be useful and marketable or it can be consid ...
, and this mixture, called "KA Oil" for ketone-alcohol oil, is the main feedstock for the production of adipic acid
Adipic acid or hexanedioic acid is the organic compound with the formula (CH2)4(COOH)2. From an industrial perspective, it is the most important dicarboxylic acid: about 2.5 billion kilograms of this white crystalline powder are produced annuall ...
. The oxidation involves radicals and the hydroperoxide
Hydroperoxides or peroxols are compounds containing the hydroperoxide functional group (ROOH). If the R is organic, the compounds are called organic hydroperoxides. Such compounds are a subset of organic peroxides, which have the formula ROOR. ...
C6H11O2H as an intermediate. In some cases, purified cyclohexanol, obtained by hydration of cyclohexene
Cyclohexene is a hydrocarbon with the formula C6H10. This cycloalkene is a colorless liquid with a sharp smell. It is an intermediate in various industrial processes. Cyclohexene is not very stable upon long term storage with exposure to light ...
, is the precursor. Alternatively, cyclohexanone can be produced by the partial hydrogenation
Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic ...
of phenol
Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it r ...
:
:C6H5OH + 2 H2 → (CH2)5CO
This process can also be adjusted to favor the formation of cyclohexanol.[
]ExxonMobil
ExxonMobil Corporation (commonly shortened to Exxon) is an American multinational oil and gas corporation headquartered in Irving, Texas. It is the largest direct descendant of John D. Rockefeller's Standard Oil, and was formed on November 3 ...
developed a process in which benzene is hydroalkylated to cyclohexylbenzene
Cyclohexylbenzene is the organic compound with the structural formula C6H5-C6H11. It is a derivative of benzene with a cyclohexyl substituent (C6H11). It is a colorless liquid.
Formation
Cyclohexylbenzene is produced by the acid-catalyzed alkyl ...
. This latter product is oxidized
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...
to a hydroperoxide
Hydroperoxides or peroxols are compounds containing the hydroperoxide functional group (ROOH). If the R is organic, the compounds are called organic hydroperoxides. Such compounds are a subset of organic peroxides, which have the formula ROOR. ...
and then cleaved into phenol and cyclohexanone. Therefore, this newer process without producing the acetone by-product appears attractive and is similar to the cumene process
The cumene process (cumene-phenol process, Hock process) is an industrial process for synthesizing phenol and acetone from benzene and propylene. The term stems from cumene (isopropyl benzene), the intermediate material during the process. It w ...
as a hydroperoxide is formed and then decomposed to yield two key products.
Laboratory methods
Cyclohexanone can be prepared from cyclohexanol by oxidation with chromium trioxide
Chromium trioxide (also known as chromium(VI) oxide or chromic anhydride) is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name.
This compound is a dark-purple s ...
( Jones oxidation). An alternative method utilizes the safer and more readily available oxidant sodium hypochlorite.
Uses
The great majority of cyclohexanone is consumed in the production of precursors to Nylon 6,6
Nylon 66 (loosely written nylon 6-6, nylon 6/6, nylon 6,6, or nylon 6:6) is a type of polyamide or nylon. It, and nylon 6, are the two most common for textile and plastic industries. Nylon 66 is made of two monomers each containing 6 carbon atoms ...
and Nylon 6
Nylon 6 or polycaprolactam is a polymer, in particular semicrystalline polyamide. Unlike most other nylons, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization; this makes it a special case in the compari ...
. About half of the world's supply is converted to adipic acid
Adipic acid or hexanedioic acid is the organic compound with the formula (CH2)4(COOH)2. From an industrial perspective, it is the most important dicarboxylic acid: about 2.5 billion kilograms of this white crystalline powder are produced annuall ...
, one of two precursors for nylon 6,6
Nylon 66 (loosely written nylon 6-6, nylon 6/6, nylon 6,6, or nylon 6:6) is a type of polyamide or nylon. It, and nylon 6, are the two most common for textile and plastic industries. Nylon 66 is made of two monomers each containing 6 carbon atoms ...
. For this application, the KA oil (see above) is oxidized with nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...
. The other half of the cyclohexanone supply is converted to cyclohexanone oxime. In the presence of sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...
catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
, the oxime rearranges to caprolactam
Caprolactam (CPL) is an organic compound with the formula (CH2)5C(O)NH. This colourless solid is a lactam (a cyclic amide) of caproic acid. Global demand for this compound is approximately five million tons per year, and the vast majority is us ...
, a precursor to nylon 6
Nylon 6 or polycaprolactam is a polymer, in particular semicrystalline polyamide. Unlike most other nylons, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization; this makes it a special case in the compari ...
:[
::
]
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. It forms a trimethylsilylenol ether upon treatment with trimethylsilylchloride
Trimethylsilyl chloride, also known as chlorotrimethylsilane is an organosilicon compound ( silyl halide), with the formula (CH3)3SiCl, often abbreviated Me3SiCl or TMSCl. It is a colourless volatile liquid that is stable in the absence of water. ...
in the presence of base. It also forms an enamine with pyrrolidine.
Illicit use
Cyclohexanone has been used in the illicit production of phencyclidine and its analogs and as such is often subject to additional checks before purchase.
Safety
Like cyclohexanol
Cyclohexanol is the organic compound with the formula HOCH(CH2)5. The molecule is related to cyclohexane by replacement of one hydrogen atom by a hydroxyl group. This compound exists as a deliquescent colorless solid with a camphor-like odor, ...
, cyclohexanone is not carcinogenic and is moderately toxic, with a TLV of 25 ppm for the vapor. It is an irritant.[
]
References
{{Authority control
6
IARC Group 3 carcinogens