Oxidation of isopropanol

At low acidity the relative rates of oxidation of isopropanol and (CH3)2CDOH (contaminated with light isopropanol) were found to be 6.4+1.9 at 40 °C after correction for incomplete deuteration has also been determined and the... 

The resolution of the overall reaction into steps implied by the steric effect (above) has been achieved" for the oxidation of isopropanol. In 97% aqueous acetic acid a rapid reaction, ic2 x 1.25x10 l.mole . sec (15 °C, p = 0.183 Af NaC104), which is unaffected by deuteration, precedes the oxidation. Evidence for an intermediate has been reported for the oxidation of 1,1,1-tri-fluoro-2-propanol at very high acidities . 

Interest has been shown by several groups on the effect of solvent and of added anions upon the oxidation of alcohols. The oxidation of isopropanol proceeds 2500 times faster in 86.5 % acetic acid than in water at the same hydrogen ion concentration . The kinetics and primary kinetic isotope effect are essentially the same as in water. Addition of chloride ion strongly inhibits the oxidation and the spectrum of chromic acid is modified. The effect of chloride ion was rationalised in terms of the equilibrium,... 

The intercalation of anionic species into LDHs is an interesting alternative for the immobilization of catalytic complexes. Special attention is being paid to LDHs containing bulky and stable anions, e.g. polyoxometalates (POMs), since they can give rise to a wide range of microporous materials [4]. Many years ago, Pinnavaia et al. reported the intercalation of POM anions into LDHs, and found that the products showed significant photo-catalytic activity in the oxidation of isopropanol to acetone in the presence... 

The mechanism of photo-oxidation of alcohols over Ti02 is not certain. Bickley (206, 405) postulates that the oxidation of isopropanol occurs via attack by OJ to form an aldehydic intermediate, which is then further oxidized by H202 or OH- to form acetone whereas Formenti and Teichner (406) suggest that oxidation occurs via a mononuclear oxygen species which at higher temperatures may involve activated lattice ions (417). This latter suggestion is very similar to the work on UV formation of O ions on the surface in a variety of oxides which have been reviewed previously (1). 

In general, any of several possibile mechanisms may be operative for complex reactions. For example, in the oxidation of isopropanol by RuIV the key redox step could involve initial outer-sphere electron transfer, initial H-atom transfer, or even two-electron hydride transfer. The hydride mechanism, which has been proposed to be the actual low-energy pathway in water at 25 °C, is illustrated in reaction (3).2... 

Hydroperoxy-2-hydroxypropane has, in fact, been isolated from photocatalysed oxidation of isopropanol. 

The NADP-dependent TBADH was used for the laboratory-scale preparation of several chiral aliphatic and cyclic hydroxy compounds by reduction of the corresponding ketones. For the regeneration of NADPH, this reduction reaction can be coupled with the TBADH catalyzed oxidation of isopropanol. For the reduction of some ketones it was observed that the reaction rate was increased in the presence of the regenerating substrate isopropanol, for instance in the presence of 0.2 v/v isopropanol, the reduction rate of butanone or pentanone was increased 3-4-fold [57], In some cases, the enantiomeric excess of the reduction reaction is not very high, especially when small molecules are converted, but also for compounds such as acetophenone [138]. 

R)-alcohols in high enantiomeric excess can be obtained with the aid of the NADP-dependent ADH from Lactobacillus kefir. Due to the broad substrate specificity of this enzyme, aromatic, cyclic, polycyclic as well as aliphatic ketones can be reduced. A simple method for the regeneration of NADPH is given by the simultaneously coupled oxidation of isopropanol by the same enzyme. Several chiral alcohols (Table 8) were synthesized at a 2.5 mmol scale within a reaction time of 12-36 h [160]. 

Scheme 4.101). The cofactor NADH was regenerated by the simultaneous oxidation of isopropanol to acetone. 

A second process involves oxidation of isopropanol to acetone and H202 in either vapor or liquid phases at 15 to 20 atm and 100°C. 

Another interesting feature of the AMO photocatalysts is the effect of diluent substrates such as MgO or activated C. Addition of substrates causes an increase in the rate of photoassisted catalytic oxidation of isopropanol. A synergistic effect is clear specific amounts of diluent lead to an increase. Too much or too little diluent leads to a decrease in rate. The exact explanation of this synergistic effect is not known, however, it may related to the ability of species such as OH or adsorbed hydrocarbons and intermediates to travel back and forth across the AMO/substrate interface. There does not seem to be a correlation of rate with the surface area, acid base character, particle size or other physical/chemical properties of the substrate. 

Acetone and hydrogen peroxide are produced with a selectivity of 80% upon multistage oxidation of isopropanol with air at 15 to 20 bar and 90 to I40°C ... 

The oxidation of isopropanol process is used only in a few plants in Russia and the electrochemical processes are currently utilized only in a few plants in Western Europe because of the high operating costs due to the large use of electricity. Because of their minor importance in H202 production [126], they will not be discussed further. The anthraquinone process accounts for 95% of the H202 production. The direct reaction of H2 and 02 is a recent discovery, so it is not yet fully utilized [126], The reaction cycle is ... 

B. Location of Kinetically Significant Hydrogen Westheimer and Nicolaides62 have utilized the deuterium isotope effect to determine whether the C—H or O—H bond rupture is rate controlling in the oxidation of isopropanol by chromic acid. Isopropanol-2-di was synthesized and found to react at approximately one-sixth the rate of the all protium compound. This is conclusive evidence that C—H rather than O—H bond rupture is rate determining. 

Figure 1-13. Effect of pH on the activity of sec-alcohol dehydrogenase (Candida boidinii) during the oxidation of isopropanol in various buffers in 50 mM concentration O sodium citrate, potassium phosphate, Atriethanolamine/HCI, ATris/HCI, glycine.

Figure 16.2-49. Asymmetric reduction of ethyl-4-chloro-3-oxobutanoate catalyzed by an alcohol dehydrogenase (ADH) in recombinant E. coli. The necessary reduction equivalents were derived from the oxidation of isopropanol with the same enzyme.

Pitts et al. [480] and Beckett and Porter [61, 62] found that benzophenone sensitizes the oxidation of isopropanol in accordance with the following reaction scheme. 

Other derivatives of p-quinones, such as anthraquinone, mono- and di-sodium sulphonates are photosensitizers of the oxidation of isopropanol [Refs. 84, 105, 106, 158, 662, 663]. Lock and Sagar [377] have suggested that a similar mechanism may occur in the photosensitized oxidation of JV-alkylamides which they studied as a model system simulating the photo-sensitized degradation of polyamides. They suggest that the AT-alkyl radical initially produced may add molecular oxygen to give peroxy radicals which are the precursors of the observed oxidation reaction. 

Decomposition of the chromate ester of isopropanol likewise involves rate-limiting proton transfer from carbon in the oxidation of isopropanol to acetone in the presence of chromic oxide [10]. 

A new process for the synthesis of glycerine is based on this direct oxidation process for acrolein. Reaction of acrolein with isopropanol gives allyl alcohol and acetone as products. Hydroxylation of allyl alcohol by reaction with hydrogen peroxide, obtained from liquid-phase oxidation of isopropanol, is made to yield glycerine as a product. ... 

A group of studies in the literature deals with 2-propanol (isopropanol). " According to FTIR studies,no dissociative adsorption can be detected when isopropanol is adsorbed at a Pt surface. The main reaction of isopropanol is its dehydrogenation leading to the formation of acetone. Kinetic studies demonstrate that dehydrogenation of isopropanol is a fast reaction while the oxidation of isopropanol or acetone into CO2 is a relatively slow process. 

Figure 6.9 shows the type of multiplicity of this sort involved for a typical oxidation chain reaction, the liquid-phase oxidation of isopropanol. The overall kinetics are given by... 

Interestingly, [((C5Me5)M)2 HAT2][HAr2] catalyzes the air-oxidation of isopropanol to acetone over 3d, at 20° (Af = Rh,... 

I. V. Kozhevnikov, V. E. Taraban ko, and K. I. Matveev [Kinet. Catal., 21, 679 (1980)] have studied the oxidation of isopropanol by palladium chloride in aqueous solution over the temperature range 339 to 369 K. The stoichiometry of the reaction is... 

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