Oxidation of cyclohexanol

The uncatalysed oxidation in de-aerated solutions is first order with respect to peroxodisulphate, and zero order with respect to the substrate (Subbaraman and Santappa ). Measurements in the temperature range 55-70 C show that the first-order rate coefficient is expressed by 

The silver ion-catalysed oxidation of cyclohexanol obeys the rate equation (Subbaraman and Santappa ) 

A mechanism consistent with this rate equation is obtained by adding reactions (15) and (52) to the reactions proposed for the uncatalysed oxidation. 

---

Dilute nitric acid can be used to oxidize an aliphatic hydrocarbon. For example, a significant use for nitric acid is the oxidation of cyclohexanol and cyclohexanone (qv) to produce adipic acid (qv). Most adipic acid is used for the production of nylon-6,6. 

A few results have been reported on the oxidation of cyclohexanol by acidic permanganate In the absence of added fluoride ions the reaction is first-order in both alcohol and oxidant , the apparent first-order rate coefficient (for excess alcohol) at 25 °C following an acidity dependence k = 3.5-1-16.0 [H30 ]sec fcg/A , depends on acidity (3.2 in dilute acid, 2.4 in 1 M acid) and D2o/ H20 is f-74. Addition of fluoride permitted observation of the reaction for longer periods (before precipitation) and under these conditions methanol is attacked at about the same rates as di-isopropyl ether, although dioxan is oxidised over twenty times more slowly. The lack of specificity and the isotope effect indicates that a hydride-ion abstraction mechanism operates under these conditions. (The reactivity of di-isopropyl ether towards two-equivalent oxidants is illustrated by its reaction with Hg(II).) Similar results were obtained with buffered permanganate. 

A brief study of the oxidations of cyclohexanol and cyclohexanol-l-t/ by Tl(III) indicated the rate expression to be ... 

Two studies have been performed by Littler on the oxidation of cyclohexanol by Hg(II), the second leading to more detailed and reliable data. The reaction is first-order in both oxidant and substrate but the rate is independent of acidity. E is 24.8 kcal.mole AS is 1 eu, Ath/Acd is 3.0 and ko ol HzO 1-30-At 50 °C di-isopropyl ether is attacked at about one-half the rate of isopropanol, which implies that hydride ion abstraction is occurring in both cases. This is supported in the case of cyclohexanol by the isotope effects. 

The first term is analogous to the rate expression for the Mn(II[) oxidation of cyclohexanol vide supra) and displays a primary isotope effect of similar magnitude (2.2 at 50 °C). The second term shows an isotope effect of 4.3 for replacement of HCO2H by DCO2H. The oxidations of malonic acid and Hg(l) ° involve [Mn(III)] /[Mn(ll)] terms and these are readily explained by the equilibrium... 

This contrasts with the V(V) oxidation of cyclohexanol which exhibits an [H30 ] dependence and involves an extra water molecule in the transition... 

Br(OAc)J Oxidations of Alcohols Investigated in Micro Reactors Organic synthesis 83 [OS 83] Br(OAc)J Oxidation of cyclohexanol... 

Another recent patent (22) and related patent application (31) cover incorporation and use of many active metals into Si-TUD-1. Some active materials were incorporated simultaneously (e.g., NiW, NiMo, and Ga/Zn/Sn). The various catalysts have been used for many organic reactions [TUD-1 variants are shown in brackets] Alkylation of naphthalene with 1-hexadecene [Al-Si] Friedel-Crafts benzylation of benzene [Fe-Si, Ga-Si, Sn-Si and Ti-Si, see apphcation 2 above] oligomerization of 1-decene [Al-Si] selective oxidation of ethylbenzene to acetophenone [Cr-Si, Mo-Si] and selective oxidation of cyclohexanol to cyclohexanone [Mo-Si], A dehydrogenation process (32) has been described using an immobilized pincer catalyst on a TUD-1 substrate. Previously these catalysts were homogeneous, which often caused problems in separation and recycle. Several other reactions were described, including acylation, hydrogenation, and ammoxidation. 

This reaction was proposed in 1960 for compounds with a weak C—H bond [33] and was experimentally proved in the reactions of oxidation of cyclohexanol and tetralin [34,35], The rate of this reaction was found to obey the following equation ... 

KA Zhavnerko. Liquid-Phase Oxidation of Cyclohexanol Initiated by Hydrogen Peroxide. Ph.D. thesis, Institute of Physical Organic Chemistry, Minsk, 1969, pp. 3-19 [in Russian]. 

High values of the inhibition coefficient (/= 12-28) were detected for the first time in the oxidation of cyclohexanol [1] and butanol [2] inhibited by 1-naphthylamine. For the oxidation of decane under the same conditions, /= 2.5. In the case of oxidation of the decane-cyclohexanol mixtures, the coefficient / increases with an increase in the cyclohexanol concentration from 2.5 (in pure decane) to 28 (in pure alcohol). When the oxidation of cyclohexanol was carried out in the presence of tetraphenylhydrazine, the diphenylaminyl radicals produced from tetraphenylhydrazine were found to be reduced to diphenylamine [3]. This conclusion has been confirmed later in another study [4]. Diphenylamine was formed only in the presence of the initiator, regardless of whether the process was conducted under an oxygen atmosphere or under an inert atmosphere. In the former case, the aminyl radical was reduced by the hydroperoxyl radical derived from the alcohol (see Chapter 6), and in the latter case, it was reduced by the hydroxyalkyl radical. 

Other mediators which have been used in combination with diaphorase for the regeneration of NAD+ are riboflavin and Vitamin K3, which is 2,3-dimethyl-1,4-naphthoquinone. However, especially riboflavin is not stable enough for synthetic applications [40]. Better stability is exhibited by phenanthrolindiones as mediators. In combination with diaphorase, Ohshiro [41] showed the indirect electrochemical oxidation of cyclohexanol to cyclohexanone using the NAD+ dependent HLADH with a turnover frequency of two per hour. For an effective enzymatic synthesis, this turnover frequency, however, would be too small. In our own studies, we were able to accelerate the NAD(P)+ regeneration considerably by lowering the electron density within the... 

We then coupled the regeneration system 1 to the horse liver alcohol dehydrogenase (HLADH) catalyzed oxidation of cyclohexanol to cyclohexanone as a model system (Fig. 9). 

Kinetic studies of hexacyanoferrate(III) oxidations have included the much-studied reaction with iodide and oxidation of the TICI2 anion, of hydrazine and hydrazinium, and of phenylhydrazine and 4-bromophenylhydrazine. These last reactions proceed by outer-sphere mechanisms, and conform to Marcus s theory. Catalyzed [Fe(CN)g] oxidations have included chlororuthenium-catalyzed oxidation of cyclohexanol, ruthenium(III)-catalyzed oxidation of 2-aminoethanol and of 3-aminopropanol, ruthenium(VI)-catalyzed oxidation of lactate, tartrate, and glycolate, and osmium(VIII)-catalyzed oxidation of benzyl alcohol and benzylamine. ... 

Most of the work reported with these complexes has been concerned with kinetic measurements and suggestions of possible mechanisms. The [Ru(HjO)(EDTA)] / aq. HjOj/ascorbate/dioxane system was used for the oxidation of cyclohexanol to cw-l,3-cyclohexanediol and regarded as a model for peroxidase systems kinetic data and rate laws were derived [773], Kinetic data were recorded for the following systems [Ru(Hj0)(EDTA)]702/aq. ascorbate/dioxane/30°C (an analogue of the Udenfriend system cyclohexanol oxidation) [731] [Ru(H20)(EDTA)]70j/water (alkanes and epoxidation of cyclic alkenes - [Ru (0)(EDTA)] may be involved) [774] [Ru(HjO)(EDTA)]702/water-dioxane (epoxidation of styrenes - a metallo-oxetane intermediate was postulated) [775] [Ru(HjO)(EDTA)]7aq. H O /dioxane (ascorbic acid to dehydroascorbic acid and of cyclohexanol to cyclohexanone)... 

H202 decomposes to free radicals in 2-propanol by the action of H+. Free radicals are also produced by the reaction between tert-BuOOH and Br in 1-propanol. The HCOf ions inhibit the oxidation of cyclohexanol initiated by AIBN, destroying many oxyperoxide radicals—i.e., HCOf is a negative catalyst. Appropriate reaction schemes and rate equations are proposed. 

Negative Catalysis by JfC03 Ions in Chain Oxidation of Cyclohexanol... 

The inhibiting effect of NaHC03 on chain oxidation was established by studying the effect of ions on the oxidation of cyclohexanol. The latter was oxidized at 75°C. with AIBN as initiator (R = 6.9 X 107 mole liter"1 sec."1). To dissolve NaHC03, 9% of water was added to cyclohexanol. The rate of oxidation was measured volumetrically. 

Adipic acid has been prepared by the following methods the action of silver1 or copper 2 on /3-iodopropionic acid the reduction of mucic add with phosphorus and iodine 3 the electrolysis of the potassium or sodium salts of monoethyl succinate 4 the condensation of ethylene chloride or bromide with malonic ester or cyanoacetic ester and subsequent hydrolysis 5 the oxidation of certain fractions of Baku petroleum 6 the oxidation of cyclohexanol or cyclohexanone with nitric acid 7 or potassium permanganate.8... 

Table IV. Solvent Effects in the Oxidation of Cyclohexanol to Adipic Acid (Reaction Conditions Cyclohexanol, 5 mL Oxygen,...

The oxidation of cyclohexanol to cyclohexanone with fluorine and aqueous acetonitrile was performed in a single-channel microreactor operated under annular flow at room temperature. A conversion of 84% and a selectivity of 74% were observed [313], In a similar way, diols such as 1,2-cyclohexanediol were partly or fully oxidized. A 53% selectivity to the monooxidation product was obtained at a conversion of 87% the dioxidation product was obtained with 30% yield. 

All that remains is to make cyclohexanone by oxidation of cyclohexanol. 

Figure 8.4 Oxidation of cyclohexanol and cyclohexanone by HN03 to give adipic acid. V5+ and Cu2+ are in catalytic amounts. NO and NOz are recycled, but some HN03 is lost as N2 and N20 (a greenhouse gas).

Fig. 12 Oxidation of cyclohexanol catalyzed by HLADH with acetaldehyde as a coenzyme regenerating substrate...

Gelbard has used peroxotungstates supported on polypyridine polymers in the epoxidation of cyclohexene with hydrogen peroxide.66 Polypyridine polymers were also used to support heteropolyperoxometallates for use in the oxidation of alcohols with hydrogen peroxide.67 The tetranuclear complex [cetylpyridinium chloride][P04 WO(02)2 4] supported on polypyridine was found to be an effective catalyst for the oxidation of cyclohexanol to cyclohexanone, also with hydrogen peroxide. 

---