Oxidation to acetone

A similar system based on rhodium has been studied (123) and was found to be less active than the equivalent iridium catalysts. Selective hydrogenation of acetylenes to olefins and dienes to monoolefins can be performed using the rhodium system, and the authors note that although propan-2-ol is an effective source of hydrogen (via oxidation to acetone), mild pressures of hydrogen gas can also be employed. 

The presence of cationic surface sites on carbon blacks which had been treated with oxygen in the presence of acid was confirmed by Rivin (83) by various hydride-transfer reactions. Isopropanol was oxidized to acetone in refluxing 50% sulfuric acid ... 

This molecule is called cumene, and it is easily oxidized to acetone and phenol, both important commodity chemicals,... 

More recently, it was demonstrated that 80 is a catalyst for the partial oxidation of olefins using dioxygen (230). For example, dry propene was oxidized to acetone when water vapor was present in the catalyst stream, some propanal could also be detected. Other reactions reported included the conversion of styrene to acetophenone and phenylacetaldehyde in an 80 20 product ratio, and 2-norbornene to 2-norbomanone and cyclohexene-4-carboxyaldehyde in a 70 30 product ratio. 

Methyl Methacrylate. The principal chemical use for propylene is hydration to isopropyl alcohol. This in turn can be oxidized to acetone and thence by a series of reactions, requiring hydrogen cyanide and methanol which are likewise derivable from petroleum, converted to methyl methacrylate as outlined below. 

A study of oxidation of HMSA was done relative to pinacol to estimate the absolute rate of oxidation of HMSA with OH radicals in solution. Pinacol was oxidized to acetone in Fenton s oxidation. Anbar and Neta (1967) reported reaction rates of OH radicals with pinacol and acetone of 3.2 x 108 Mr1 s 1 and 4.3 x 107 Mr1 s, respectively. Table 6.1 presents the oxidation rates of pinacol (10-2 M) and pinacol-HMSA (10-2 M each). The concentrations of the reactants were Fe2+ = 104 M, H202 = 0.1 M, and pH 2. Oxidation rates for each molecule were different in separated and mixed reactions, as the steady-state concentration of free radicals depends on the chemistry of organic substrates in solution. HMSA is more reactive than pinacol by a factor of 3.9 0.8. If the absolute rate of reaction of pinacol with OH radicals was calculated to be 3.2 x 108 M 1 s, then ... 

The chromium leaves, taking the bonding electron pair with it. Overall, 2-propanol has been oxidized to acetone, and the chromium has been reduced from the +6 oxidation state in H2C1O4 to the +4 oxidation state in H2OO3. The mechanism has additional steps that result in the final oxidation state of the chromium being +3. 

Recently, Capon and Wu49 have reported the generation of secondary enamines from their TV-trimethylsilyl derivatives through hydrolysis. In DMSO-d6 (99% v/v)-D20 (1% v/v) solution, enamine 40 is converted to the TV-deuteriated enamine 41 quantitatively in 5-10 min at room temperature. The solution obtained is stable for several hours, but over a period of 2-3 days 41 is oxidized to acetone and iV-deuterio-TV-phenylforma-mide. On adding 15% (v/v) D20/DC1 (0.1 M) to the solution, enamine 41 is completely hydrolyzed to 2-[2//]isobutyraldehyde and aniline without detection of any intermediates. Enamine 42 is formed by the acid-catalyzed hydrolysis of 40 (Scheme 3). Similar results are obtained with other iV-aryl enamines. 

The Wacker-Hoechst process has been practised commercially since 1964. In this liquid phase process propylene is oxidized to acetone with air at 110-120°C and 10-14 bar in the presence of a catalyst system containing PdCl2. As in the oxidation of ethylene, Pd(II) oxidizes propylene to acetone and is reduced to Pd(0) in a stoichiometric reaction, and is then reoxidized with the CuCl2/CuCl redox system. The selectivity to acetone is 92% propionaldehyde is also formed with a selectivity of 2-4%. The conversion of propylene is more than 99%. 

A somewhat more complex 4-methoxy-2-quinolone is the alkaloid foliosidine (VIII) (inp 141°-142°) from Haplophyllum foliosum Vved. (see Section VI). The 2,3-dihydroxyisopentyloxy side chain, also found in evoxine and maculosine, was shown to be present by periodic acid oxidation to acetone and an optically inactive aldehyde. 

In other redox, homogeneous catalytic reactions, palladium ions catalyze propylene oxidation to acetone 306). The Rashig process 307) is based on benzene oxidation with air in the presence of cupric and ferric chlorides. Toluene and xylene oxidize in solution containing organic salts of Co, Mn, and Mo 308,309). It is interesting to note that in some cases, reoxidation of the active metal ion to its original valence is assumed slow, for example, Cu(I) to Cu(II) 310). It is conceivable that such steps could be assisted and accelerated electrochemically. Conventional processes, then, can provide a starting point for the study and development of new electrochemical redox processes. 

Q Propan-2-ol, Me2CHOH, is oxidized to acetone (propanone) by chromium(VI) in dilute add solution by the HCr04 anion at a rate proportional to [Me2CH0H](HCr04 ][H+ ]. The rate of reaction is reduced by a factor of about 7 if the deuteriated compound Me2CDOH is used instead. Which of the following mechanisms is consistent with this evidence ... 

Trace amounts of n-propanol ( 1%) were also formed(GC). As well, trace amounts of acetone were also found however, a control experiment verified its formation from the Mn cluster-catalyzed decomposition of TBHP. Additionally, small amounts of isopropanol can also be oxidized to acetone under the reaction conditions. 

Isopropyl alcohol resembles other alcohols in showing the chemical properties characteristic of compounds which contain an alcoholic hydroxyl group. Its oxidation to acetone shows that it is a secondary alcohol, and leads to the conclusion that its structure is represented by the formula (CH3)2CHOH. Isopropyl alcohol boils at 82.1° and has the specific gravity 0.7887... 

The photoreductive dimerization of aromatic ketones with i-propanol acting as reducing agent (whereby it is oxidized to acetone) is an example of the involvement of a reactive ground state produced by a photochemical reaction ... 

---