Solvent effects cyclohexanone oxidation

Our data on the catalyzed oxidation of cyclohexanone are shown in Tables I, II, and III. The solvent effects on adipic acid yield require comment. Although solvent effects often are considered to be small in free-radical chemistry, we find that our data is consistent with the published solvent effects on the decomposition rate of benzoyl... 

Table I. Solvent Effects in the Oxidation of Cyclohexanone to Adipic Acid (Reaction Conditions Cyclohexanone, 5 mL ...

The oxidized dimer, [Fe2(TPA)20(0Ac)]3+, 41, was shown to be an efficient catalyst for cyclohexane oxidation using tert-BuOOH as a source of oxygen (69). This catalyst reacts in CH3CN to yield cyclohexanol (9 equiv), cyclohexanone (11 equiv), and (tert-butylperoxy)cyclohexane (16 equiv) in 0.25 h at ambient temperatures and pressures under an inert atmosphere. The catalyst is not degraded during the catalytic reaction as determined by spectroscopic measurements and the fact that it can maintain its turnover efficiency with subsequent additions of oxidant. Solvent effects on product distribution were significant benzo-nitrile favored the hydroxylated products at the expense of (tert-butyl-peroxy)cyclohexane, whereas pyridine had the opposite effect. Addition of the two-electron oxidant trap, dimethyl sulfide, to the catalytic system completely suppressed the formation of cyclohexanol and cyclohexanone, but had no effect on the production of (tert-butylper-oxy)cyclohexane. These and other studies suggested that cyclohexanol and cyclohexanone must arise from an oxidant different from that responsible for the formation of (tert-butylperoxy)cyclohexane. Thus, two modes of tert-BuOOH decomposition were postulated a heterolytic... 

Other examples of solvent effects in casting blends include epoxy resin/copoly-ester/tetrachloroethane polyethersulphone/poly(ethylene oxide)/cyclohexanone and mixtures of PVC with various polyacrylates in solvents such as THF One particular pair of polymers PVC/poly(ethyl acrylate) appear to be miscible but no suitable solvent has been found as yet. Homogeneous blends can only be prepared by in situ polymerisation though it is possible that miscibility is enhanced by small amounts of graft copolymer which is inevitably formed by this technique. 

Acetone in conjunction with benzene as a solvent is widely employed. With cyclohexanone as the hydrogen acceptor, coupled with toluene or xylene as solvent, the use of higher reaction temperatures is possible and consequently the reaction time is considerably reduced furthermore, the excess of cyclohexanone can be easily separated from the reaction product by steam distillation. At least 0 25 mol of alkoxide per mol of alcohol is used however, since an excess of alkoxide has no detrimental effect 1 to 3 mols of aluminium alkoxide is recommended, particularly as water, either present in the reagents or formed during secondary reactions, will remove an equivalent quantity of the reagent. In the oxidation of steroids 50-200 mols of acetone or 10-20 mols of cyclohexanone are generally employed. 

DDQ ( red = 0.52 V). It is noteworthy that the strong medium effects (i.e., solvent polarity and added -Bu4N+PFproduct distribution (in Scheme 5) are observed both in thermal reaction with DDQ and photochemical reaction with chloranil. Moreover, the photochemical efficiencies for dehydro-silylation and oxidative addition in Scheme 5 are completely independent of the reaction media - as confirmed by the similar quantum yields (d> = 0.85 for the disappearance of cyclohexanone enol silyl ether) in nonpolar dichloromethane (with and without added salt) and in highly polar acetonitrile. Such observations strongly suggest the similarity of the reactive intermediates in thermal and photochemical transformation of the [ESE, quinone] complex despite changes in the reaction media. 

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