Cyclohexanol is the
organic compound with the
formula HOCH(CH
2)
5. The molecule is related to
cyclohexane by replacement of one hydrogen atom by a
hydroxyl group. This compound exists as a
deliquescent
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance ...
colorless solid with a camphor-like odor, which, when very pure, melts near room temperature. Billions of kilograms are produced annually, mainly as a precursor to
nylon.
[Michael Tuttle Musser "Cyclohexanol and Cyclohexanone" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.]
Production
Cyclohexanol is produced by the
oxidation of
cyclohexane in air, typically using cobalt
catalyst
Catalysis () is the process of increasing the reaction rate, 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 ...
s:
[
:C6H12 + 1/2 O2 → C6H11OH
This process co-forms cyclohexanone, and this mixture ("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
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.
Alternatively, cyclohexanol can be produced by the 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 c ...
of phenol:
:C6H5OH + 3 H2 → C6H11OH
This process can also be adjusted to favor the formation of cyclohexanone.
Basic reactions
Cyclohexanol undergoes the main reactions expected for a secondary alcohol. Oxidation gives cyclohexanone, which is converted on a large scale in industry to the oxime, a precursor to caprolactam. As a laboratory exercise, this oxidation can be effected with chromic acid
The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. This kind of chromic acid may be used as a cleaning mixtu ...
. Esterification affords the commercially useful derivatives dicyclohexyladipate and dicyclohexylphthalate, which are used as plasticizers. Heating in the presence of acid catalysts converts cyclohexanol to 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 ...
.[
]
Structure
Cyclohexanol has at least two solid phases. One of them is a plastic crystal.
Applications
As indicated above, cyclohexanol is an important feedstock in the polymer industry, firstly as a precursor to nylons, but also to various plasticizers
A plasticizer ( UK: plasticiser) is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture.
Plasticize ...
. Small amounts are used as a solvent.
Safety
Cyclohexanol is moderately toxic: the TLV for the vapor for 8 h is 50 ppm.[ The IDLH concentration is set at 400 ppm, based on studies on the acute oral toxicity in animals. Few studies have been done on its ]carcinogenicity
A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...
, but one study on rats found it to have co-carcinogenic effects.
Lucrecia Márquez-Rosado, Cristina Trejo-Solís 2, María del Pilar Cabrales-Romero, Evelia Arce-Popoca, Adolfo Sierra-Santoyo, Leticia Alemán-Lazarini, Samia Fatel-Fazenda, Claudia E. Carrasco-Legleu, Saúl Villa-Treviño, "Co-carcinogenic effect of cyclohexanol on the development of preneoplastic lesions in a rat hepatocarcinogenesis model", ''Molecular Carcinogenesis'', Vol. 46, No. 7, Pages 524 - 533, March 2007.
References
{{Chemical agents
Cyclohexyl compounds
Cycloalkanols
Nerve agent precursors