Oxidation of acetophenones

Oxidation of acetophenone with selenium dioxide iu the i)reseiice of dioxan or ethyl alcohol as solvent affords j.henylglyoxal ... 

A three-step process involving the oxidation of acetophenone, hydrogenation of the ketone to a-phenylethanol, and dehydration of the alcohol to styrene was practiced commercially by Union Carbide (59) until the early 1960s. Other technologies considered during the infancy of the styrene industry include side-chain chlorination of ethylbenzene followed by dehydrochlotination or followed by hydrolysis and dehydration. 

Ethyl benzoylformate has been prepared by the direct esterification of the acid 1 and by the action of oxides of nitrogen on an alcoholic suspension of indigo.2 The acid has been prepared by many different reactions but the most practical are the hydrolysis of benzoyl cyanide,3 the oxidation of acetophenone 4 and the oxidation of mandelic acid.5... 

Kinetic data exist for all these oxidants and some are given in Table 12. The important features are (i) Ce(IV) perchlorate forms 1 1 complexes with ketones with spectroscopically determined formation constants in good agreement with kinetic values (ii) only Co(III) fails to give an appreciable primary kinetic isotope effect (Ir(IV) has yet to be examined in this respect) (/ ) the acidity dependence for Co(III) oxidation is characteristic of the oxidant and iv) in some cases [Co(III) Ce(IV) perchlorate , Mn(III) sulphate ] the rate of disappearance of ketone considerably exceeds the corresponding rate of enolisation however, with Mn(ril) pyrophosphate and Ir(IV) the rates of the two processes are identical and with Ce(IV) sulphate and V(V) the rate of enolisation of ketone exceeds its rate of oxidation. (The opposite has been stated for Ce(IV) sulphate , but this was based on an erroneous value for k(enolisation) for cyclohexanone The oxidation of acetophenone by Mn(III) acetate in acetic acid is a crucial step in the Mn(II)-catalysed autoxidation of this substrate. The rate of autoxidation equals that of enolisation, determined by isotopic exchange , under these conditions, and evidently Mn(III) attacks the enolic form. 

Benzoylformic acid can be prepared by the oxidation of acetophenone with potassium permanganate in alkaline solution,1 by the oxidation of mandelic acid with potassium perman-... 

Another important variant of the preceding approach is the cycloaddition reaction between monocarbonyl iodonium salt 47 and an alkene to give dihydrofuran 48 (88TL3703 89JOC2605). The iodonium salt 47 is generated by the oxidation of acetophenone silyl enol ether (46) with iodosobenzene in the presence of fluoboric acid. 

In addition, the presence of an oxygen atom in the side chain also promotes the reaction. For instance, the oxidation of acetophenone proceeds easily ... 

Formerly, benzoic acid was produced by the decarboxylation of phthalic anhydride. Oxidation of acetophenon, benzyl bromide, and toluene with sulfur and water has been described in the literature, but are not commercially feasible routes of synthesis. Carboxylation of benzene with carbon dioxide is not practical due to the instability of benzoic acid at the required reaction conditions [8]. 

The observed substituent effect on the reaction rate in the oxidation of substituted aliphatic ketoximes by /V-bromosaccharin has been rationalized in terms of a mechanism.126 The oxidation of acetophenones with N-bromophthalimidc exhibited a linear correlation with Brown s a+ with reaction constant p = —0.52. An Exner plot gave an isokinetic temperature p = 263 K. A mechanism consistent with the kinetic data has been proposed.127... 

Phenylglyoxal has been prepared from isonitrosoacetophenone through the bisulfite compound 2,3 or by treatment with nitro-sylsulfuric acid 4 or with nitrous acid.3 It also has been prepared by the oxidation of benzoylcarbinol with copper acetate,6 by heating bromophenacyl acetate,7 and by the oxidation of acetophenone with selenium dioxide.1... 

Valechha, N. D., Sewanee, J. P. Kinetics of oxidation of acetophenones by selenium dioxide. J. Indian Chem. Soc. 1986, 63, 970-973. Hassan, R. M. Kinetics and mechanism of selenium(IV) oxidation of ascorbic acid in aqueous perchlorate solutions. Croat. Chem. Acta 1991,64, 229-236. 

Kinetic studies of oxidation of acetophenone oximes with CBT in aqueous acetic acid were carried out (86MI1). The main reaction products are acetophenones. The scheme of oxidation, complying with the kinetic data and the effects of the acidity of the medium and the addition of chloride ions, proposes that the attack of positively charged chlorine on the oxime group nitrogen is the rate-limiting stage, followed by the fast transformation of the carbocation formed (Scheme 105). 

The Haloform reaction is catalyzed by cyclodextrins in what the authors label as inverse phase transfer catalysis, 25 but the synthetic utility of this variation remains to be seen. An alternative to the use of halogen is a nitroarene catalyzed oxidation of acetophenone with sodium percarbonate or sodium perborate.26 However, the yields of substituted benzoic acids furnished by this method are mediocre (23-73%) in comparison to the conventional Haloform conditions. Likewise, the Haloform reaction of acetone with iodine in liquid ammonia is without synthetic merit (8-12%).27... 

When benzaldehyde reacts with a peroxy acid, the product is benzoic acid. The mechanism for this reaction is analogous to the one just given for the oxidation of acetophenone, and the outcome illustrates the greater migratory aptitude of a hydrogen atom compared to phenyl. Outline all the steps involved. 

For oxidation of acetophenone oximes by V03, see under Oximes. Oxidation of thioketones is described later. 

VR Chumbhale, SA Paradhy, M Anilkumar, et al. Vapour phase oxidation of acetophenone to benzoic acid over binary oxides of V and Mo. Chemical Engineering Research and Design, 83(1) 75-80, 2005. 

Aldehydes are generally easily oxidized to carboxylic acids. Their reducing property is utilized for their detection (Tollens , Fehling s, Benedict s, Nessler s, and Feder s reagents). The acid formed can be isolated and serve for identification as such, or it can be converted to a suitable derivative. Of course, the reaction is not specific. For example, benzoic acid is not only obtained by oxidizing benzaldehyde, but also on oxidation of acetophenone. 

Substituted 2,5-dimethoxyacetophenones can be oxidized directly to quinone acetic acid esters (156) by using a modification of Taylor and McKillop s original procedure for the oxidation of acetophenones to phenyl acetates by thallium(ili) nitrate. The product is usually contaminated with small amounts of the a-methoxy-derivative cf. 3, 75). 

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