Hydrocarbons oxidation with chromic acid

A method ) has been recommended for the determination of benzene in the presence of its homologues. It is based on nitration of a mixture of aromatic hydrocarbons, extraction with ether of the nitro-compounds formed from the reaction mixture, evaporation of the solvent, oxidation with chromic acid and dissolution of the residue in acetic acid. 

Work has been concentrated on hydrocarbons containing activating groups, such as phenyl or /err-butyl, in order to achieve convenient rates of reaction. The relative rates of oxidation of two series of hydrocarbons with chromic acid in 95 % acetic acid are ... 

The effect of adding large quantities of acetic acid to the medium is more complicated. The acceleration of the oxidation rate of isopropanol was ascribed initially to a shift of the esterification equilibrium to the right (reaction 29). However, RoCek found that acceleration by acetic acid occurs for oxidations which cannot involve a pre-equilibrium esterification, e.g. those of aliphatic and alicyclic hydrocarbons. The obvious alternative, i.e. that acetic acid combines with chromic acid, viz. 

Oxidation of 3-phenyl-7-hydroxybenzothiophene with Fremy s salt afforded, in almost equal amounts, 3-phenyl derivatives of 156 and 157 (70MI3). Difficulties were encountered in the preparation of quinones from substituted alkyl benzothienyl-3-acetates. The only successful conversion of ethyl 6-hydroxy-5-methoxybenzothienyl-3-acetate was in a two-phase system with either aqueous periodate or thallate. The quinone was obtained in low yield (79JHC231). Some exteneded analogs could be prepared directly from the hydrocarbons with chromic acid (53CB366 56JCS3435). 

Oxidations with chromic oxide encompass hydroxylation of methylene [544] and methine [544, 545, 546] groups conversion of methyl groups into formyl groups [539, 547, 548, 549] or carboxylic groups [550, 55i] and of methylene groups into carbonyls [275, 552, 553, 554, 555] oxidation of aromatic hydrocarbons [556, 557, 555] and phenols [559] to quinones, of primary halides to aldehydes [540], and of secondary halides to ketones [560, 561] epoxidation of alkenes [562, 563,564, and oxidation of alkenes to ketones [565, 566] and to carboxylic acids [567, 565, 569]. 

The oldest process of organic electrochemistry is the indirect oxidation of hydrocarbons with chromic acid. It has been employed industrially for more than 90 years by Hoechst— now Clariant—in Gersthofen, Germany [102]. Other sites are or were located in Great Britain. The oxdiations of naphthalene, anthracene, and camphene are examples. Companies like Emery Industries, L. B. Holliday, and Boots have also used chromic acid regeneration commercially [103]. It has been employed for the bleaching of montan waxes for more than 70 years. 

These changes become still more pronounced if a third ring is fused. Anthracene is still colourless, but adds maleic anhydride. The isomeric phenanthrene does not but can be oxidized only with chromic acid. The third ring in triphenylene makes it the least reactive hydrocarbon of the isomers. 

By oxidation of the methyl derivative of an aromatic hydrocarbon with a solution of chromic anhydride in acetic anhydride and acetic acid. The aldehyde formed is immediately converted into the (/m-diacetate, which is stable to oxidation. The diacetate is collected and hydrolysed with sulphuric acid, for example ... 

A quantity of earlier work exists on chromic acid oxidation of hydrocarbons. It was noted that diphenylmethane and other hydrocarbons in glacial acetic acid solution are oxidised rapidly during the initial stages but that reaction is auto-retarded The autoretardation is eliminated on adding 2.5 % of sulphuric acid. The orders of the reaction with respect to diphenylmethane and Cr(VI) are one and two respectively , the latter differing from that found by Wiberg and... 

The compound in which the 3-keto group is reduced to a hydrocarbon interestingly still acts as an orally active progestin. The preparation of this compound starts with the hydrolysis of dihydrobenzene (13-2) to afford 19-nortestosterone (15-1). Reaction with ethane-1,2-thiol in the presence of catalytic acid leads to the cyclic thioacetal (15-2). Treatment of this intermediate with Raney nickel in the presence of alcohol leads to the reduced desulfurized derivative (15-3). The alcohol at 17 is then oxidized by any of several methods, such as chromic acid in acetone (Jones reagent), and the resulting ketone (15-4) treated with hthium acetylide. There is thus obtained the progestin lynestrol (15-5) [18]. 

Chromic acid oxidation of saturated hydrocarbons starts with hydrogen abstraction to give a caged radical pair.113,114 The collapse of the latter leads to a chromium(IV) ester, which hydrolyzes to the product tertiary alcohol. The postulation of the caged pair was necessary to explain the high degree of retention in oxidation of (+)-3-methylheptane 113... 

Reaction LXX. Oxidation of certain Hydrocarbons. (B., 14, 1944 A. Spl., 1869, 300 E.P., 1948 (1869).)—This reaction is confined in the aliphatic series almost exclusively to the replacement by hydroxyl of the hydrogen attached to tertiary carbon atoms. A powerful oxidising agent, e.g., chromic acid in glacial acetic acid, is necessary. In the aromatic series the reaction is somewhat more easy to accomplish when the sodium salt of anthraquinone-jS-monosulphonic acid, for example, is fused under pressure with caustic soda and a little potassium chlorate, replacement of both a hydrogen atom and the sulphonic acid group by hydroxyl occurs, and alizarin ( /f-dihydroxyanthraquinone) is obtained. 

Polycyclic quinones are prepared by careful oxidation of the corresponding hydrocarbons with chromic-sulfuric acid mixture in acetic acid solution or as an agitated aqueous suspension, e.g., 2,3-dimethy 1-1,4-naphthoquinone (80%), 9,10-phenanthroquinone (80%), and acenaphthene-quinone (60%). A laboratory reactor has been described in which an acetic acid solution of chromic acid and another solution of hydrocarbon are mixed as a film at 90°. The reaction mixture is then fed into water to prevent ftirther oxidation. By this procedure, the yield of 2-methyl-1,4-naphthoquinone has been raised from 29% by the usual process to... 

Introduction. The quinones are intermediate products in the oxidation of the aromatic nucleus. They may be prepared in some cases by the direct oxidation of aromatic hydrocarbons. For example, anthracene, naphthalene, and phenanthrene are oxidized to the corresponding quinones by chromic acid mixtures. Quinones are prepared more conveniently by oxidation of primary aromatic amines, particularly the p-substituted amines. p-Benzoquinone is obtained by the oxidation of aniline, p-toluidine, sulfanilic acid, p-aminophenol, and other similar compounds. Similarly the a-naph-thoquinone is obtained by oxidation of 1,4-aminonaphthol, and /9-naphthoquinone by the oxidation of 1,2-aminonaphthol. In the laboratory, although it is possible to prepare p-benzoquinone by the oxidation of aniline with acid-dichromate mixture, the method is tedious and the yield poor. Since hydroquinone is used extensively as a photographic developer and is made industrially, it is more convenient to prepare quinone by its oxidation. 

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