Cyclohexanone is an organic compound with the molecular formula (CH2)5CO. The molecule consists of a six-carbon ring molecule with a ketone functional group. The smell of the colorless oil is reminiscent of acetone. Over time, cyclohexanone samples appear yellow. Cyclohexanone is slightly soluble in water and miscible with common organic solvents. Billions of kilograms are produced each year, mainly as a precursor to nylon.
Cyclohexanone is produced by oxidation of cyclohexane in air, usually using a cobalt catalyst:
C6H12 + O2 → (CH2)5CO + H2O
This process together forms cyclohexanol, a mixture known as the “KA oil” of ketol oils, which is the main raw material for the production of adipic acid. Oxidation involves the intermediates of radical and hydroperoxide C6H11O2H. In some cases, purified cyclohexanol obtained by hydration of cyclohexene is the precursor. Alternatively, cyclohexanone can be produced by partial hydrogenation of phenol:
C6H5OH + 2 H2 → (CH2)5CO
The process can also be adjusted to favor cyclohexanol formation.
Exxonmobil developed a process for hydroalkylation of benzene to cyclohexylbenzene. The latter product is oxidized to hydroperoxides, which are then cleaved to phenol and cyclohexanone. Thus, this new process, which does not produce acetone by-products, looks attractive and similar to the isopropylbenzene process in that hydroperoxides are formed and then broken down to produce two key products.
Cyclohexanone can be prepared from cyclohexanol by oxidation with chromium trioxide (Jones oxidation). Another method uses a safer and more readily available oxidant, sodium hypochlorite.
In addition to the large-scale reactions carried out in the polymer industry, many reactions for cyclohexanone have been developed. In the presence of light, it undergoes α -chlorination to form 2-chlorocyclohexanone. Trimethylsilanol ether is formed by treating trimethylsilanyl chloride in the presence of base. It also forms enamines with pyrrolidine.
Cyclohexanone has been used in the illegal production of phencyridine and its analogues, so additional checks are often required before purchase.
Like cyclohexanol, cyclohexanone is non-carcinogenic and moderately toxic, with a vapor TLV of 25 PPM. It’s an irritant.