Cyclohexanone is the
organic compoundAn organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with the
formulaA chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
(CH
2)
5CO. The molecule consists of six-carbon
cyclic moleculeAn alicyclic compound is an organic compound that is both aliphatic and cyclic. They contain one or more all-carbon rings which may be either saturated or unsaturated, but do not have aromatic character...
with a
ketoneIn organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
functional group. This colorless oil has an odor reminiscent of peardrop sweets as well as
acetoneAcetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
. Over time, samples assume a yellow color due to oxidation. Cyclohexanone is slightly soluble in water (5-10 g/100 mL), but miscible with common organic solvents. Billions of kilograms are produced annually, mainly as a precursor to
nylonNylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...
.
Production
Cyclohexanone is produced by the oxidation of
cyclohexaneCyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which being intermediates used in the production of nylon...
in air, typically using cobalt catalysts:
- C6H12 + O2 → (CH2)5CO + H2O
This process co-forms
cyclohexanolCyclohexanol is the organic compound with the formula 5CHOH. The molecule is related to cyclohexane ring by replacement of one hydrogen atom by a hydroxyl group. This compound exists as a deliquescent colorless solid, which, when very pure, melts near room temperature...
, and this mixture, called "KA oil" for ketone-alcohol oil, is the main feedstock for the production of
adipic acidAdipic acid is the organic compound with the formula 42. From the industrial perspective, it is the most important dicarboxylic acid: About 2.5 billion kilograms of this white crystalline powder are produced annually, mainly as a precursor for the production of nylon...
. The oxidation involves radicals and the intermediacy of the hydroperoxide C
6H
11O
2H. In some cases, purified cyclohexanol, obtained by hydration of
cyclohexeneCyclohexene 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...
, is the precursor. Alternatively, cyclohexanone can be produced by the partial
hydrogenationHydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...
of
phenolPhenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
:
- C6H5OH + 2 H2 → (CH2)5CO
This process can also be adjusted to favor the formation of cyclohexanol.
Laboratory methods
Cyclohexanone can be prepared from cyclohexanol by oxidation with chromic oxide.
Uses
The great majority of cyclohexanone is consumed in the production of precursors to Nylon 6,6 and
Nylon 6Nylon 6 or polycaprolactam is a polymer developed by Paul Schlack at IG Farben to reproduce the properties of nylon 6,6 without violating the patent on its production. Unlike most other nylons, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization. This makes...
. About half of the world's supply is converted to
adipic acidAdipic acid is the organic compound with the formula 42. From the industrial perspective, it is the most important dicarboxylic acid: About 2.5 billion kilograms of this white crystalline powder are produced annually, mainly as a precursor for the production of nylon...
, one of two precursors for nylon 6,6. For this application, the KA oil (see above) is oxidized with
nitric acidNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
. The other half of the cyclohexanone supply is converted to the
oximeAn oxime is a chemical compound belonging to the imines, with the general formula R1R2C=NOH, where R1 is an organic side chain and R2 may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted oximes form a closely related family of compounds...
. In the presence of
sulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
catalyst, the oxime
rearrangesThe Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann , is an acid-catalyzed rearrangement of an oxime to an amide...
to
caprolactamCaprolactam is an organic compound with the formula 5CNH. This colourless solid is a lactam or a cyclic amide of caproic acid. Approximately 2 billion kilograms are produced annually...
, a precursor to
nylon 6Nylon 6 or polycaprolactam is a polymer developed by Paul Schlack at IG Farben to reproduce the properties of nylon 6,6 without violating the patent on its production. Unlike most other nylons, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization. This makes...
:
-
Safety
Like
cyclohexanolCyclohexanol is the organic compound with the formula 5CHOH. The molecule is related to cyclohexane ring by replacement of one hydrogen atom by a hydroxyl group. This compound exists as a deliquescent colorless solid, which, when very pure, melts near room temperature...
, cyclohexanone is not carcinogenic and is only moderately toxic, with a
TLVThe threshold limit value of a chemical substance is a level to which it is believed a worker can be exposed day after day for a working lifetime without adverse health effects. Strictly speaking, TLV is a reserved term of the American Conference of Governmental Industrial Hygienists...
of 25 ppm for the vapor. It is an irritant.
A recent study of plastic tubing used in medical procedures that circulate blood outside the body suggests a link between this compound and decreased heart function, swelling, loss of taste and short term memory loss.