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The oxidation of primary alcohols to carboxylic acids can be carried out using a variety of reagents, but O 2 /air and nitric acid dominate as the oxidants on a commercial scale. Large scale oxidations of this type are used for the conversion of cyclohexanol alone or as a mixture with cyclohexanone to adipic acid. Similarly cyclododecanol is ...
Adipic acid or hexanedioic acid is the organic compound with the formula (CH 2) 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 annually, mainly as a precursor for the production of nylon .
Cyclohexanone is produced by the oxidation of cyclohexane in air, typically using cobalt catalysts: [11]. C 6 H 12 + O 2 → (CH 2) 5 CO + H 2 O. This process forms cyclohexanol as a by-product, and this mixture, called "KA Oil" for ketone-alcohol oil, is the main feedstock for the production of adipic acid.
Although rather unreactive, cyclohexane undergoes autoxidation to give a mixture of cyclohexanone and cyclohexanol. The cyclohexanone–cyclohexanol mixture, called "KA oil", is a raw material for adipic acid and caprolactam, precursors to nylon. Several million kilograms of cyclohexanone and cyclohexanol are produced annually. [9]
This process coforms 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 C 6 H 11 O 2 H. Alternatively, cyclohexanol can be produced by the hydrogenation of phenol: C 6 H 5 OH + 3 H 2 → C 6 H 11 OH
1,6-Hexanediol is industrially made by the hydrogenation of adipic acid or its esters. [ 3 ] [ 5 ] Laboratory preparation could be achieved by reduction of adipates with lithium aluminium hydride , although this method is impractical on a commercial scale.
Acid chlorides can be reduced to give aldehydes with sterically hindered hydride donors. The reducing agent DIBAL-H (diisobutylaluminium hydride) is often used for this purpose, although it normally reduces any carbonyl. DIBAL-H can selectively reduce acid chlorides to the aldehyde level if only one equivalent is used at low temperatures. [12]
Benzene is converted to cyclohexylbenzene by acid-catalyzed alkylation with cyclohexene. [6] Cyclohexylbenzene is a precursor to both phenol and cyclohexanone. [7] Hydration of cyclohexene gives cyclohexanol, which can be dehydrogenated to give cyclohexanone, a precursor to caprolactam. [8] The oxidative cleavage of cyclohexene gives adipic acid.