Cyclohexanol: dehydration oxidation

Nylon 6,6. Phenol is hydrogenated, or cyclohexane is cata-lytically oxidized with air, and the resulting cyclohexanol is oxidized to adipic acid. Dehydration of ammonium adipate then yields adiponitrile, which is hydrogenated to hexamethylenediamine. Equivalent amounts... 

No atoms are lost in the cleavage reaction so that cheap cyclohexene 6 is used to make adipic acid 7 for nylon manufacture. Any of the oxidative cleavage methods from the last chapter could be used Vogel1 has a recipe using concentrated nitric acid on cyclohexanol 8 that presumably goes by dehydration to the alkene 6 followed by oxidation, and other methods are probably used industrially. 

Zeolite titanium beta has been tested in the liquid- and gas-phase Meerwein-Ponndorf-Verley reduction of cyclohexanones and the Oppenauer oxidation of cyclohexanols. A high selectivity towards the thermodynamically unfavourable cis-alcohol was observed, which has been ascribed to transition-state selectivity in the pores of the zeolite. Under gas-phase conditions the dehydration of alcohols to cycloalkenes is observed as a side reaction. The catalyst was found to be active even in the presence of water and ammonia. 

The commercial process for the production of nylon 6 starts with the oxidation of cyclohexane with oxygen at 160°C to a mixture of cyclohexanol and cyclohexanone with a cobalt(II) catalyst. The reaction is taken to only 4% conversion to obtain 85% selectivity. Barton and co-workers have called this the least efficient major industrial chemical process.240 They have oxidized cyclohexane to the same products using tort bu(ylhydroperoxide with an iron(III) catalyst under air (70°C for 24 h) with 89% efficiency based on the hydroperoxide. The oxidation of cyclohexanol to cyclohexanone was carried out in the same way with 99% efficiency. A cobalt catalyst in MCM-41 zeolite gave 38% conversion with 95% selectivity in 4 days at 70 C.241 These produce ferf-butyl alcohol as a coproduct. It can be dehydrated to isobutene, which can be hydro-... 

The oxo-oxidation products from cyclohexane with tBuOOH arc cyclohcxyl peroxide and its decomposition products, cyclohexanol and cyclohexanone. The relative ratio of the hydroperoxide decomposition products depends on its decomposition mechanism (see scheme). After a homolytic 0-0 bond cleavage in the peroxide, the formed alkoxy radical can undergo disproportionation, yielding equal amounts of ol/onc. A high ketone yield results from the peroxide dehydration with a Lewis acid, such as l e(OII) formed by H2O2 decomposition on free Fe. 

Bcrkani ct al. [222] proposed the transformation of an alcohol (cyclopenianol) in the presence of a ketone (cyclohexanone) as a model reaction to characterize the acidity and the basicity of oxide catalysts (Figure 3). Actually, it is a Meerwein-Ponndorf-Verley (MPV) reduction which will be discussed in section 5. The authors found a good correlation between basicity of NaCsX zeolites or K impregnated alumina and their activities for hydrogen transfer (monitored by cyclohexanol or cyclohexene production). On the other hand, the more acidic the catalyst, the higher the dehydration extent. 

Cyclohexene will undergo an ozonolysis reaction to yield adipic acid upon oxidative workup. Cyclohexene is produced from cyclohexanol by a dehydration (elimination) reaction. The synthesis of adipic acid from cyclohexanol is... 

The Grignard reaction of cyclohexanone 15 with 2,3-methylenedioxyphenyl magnesium bromide 14 in THF followed by dehydration and hydroboration-oxidation produced cyclohexanol 16, which afforded cyclohexanone derivative 17 by Jones oxidation. 

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