Benzenes chlorinated , oxidation

Hquid and gaseous reactants, Hquid products benzene chlorination, oxidation 0.01-0.2 1-30 100-500 100-500... 

The cumene oxidation route is the lea ding commercial process of synthetic phenol production, accounting for more than 95% of phenol produced in the world. The remainder of synthetic phenol is produced by the toluene oxidation route via benzoic acid. Other processes including benzene via cyclohexane, benzene sulfonation, benzene chlorination, and benzene oxychl orin ation have also been used in the manufacture of phenol. A Hst of U.S. phenol production plants and their estimated capacities in 1994 are shown in Table 2, and worldwide plants and capacities are shown in Table 3. 

Most of the phenol used in the United States is made by the oxidation of cumene, yielding acetone as a byproduct. The first stqn in the reaction yields cumene hydroperoxide, which decomposes with dilute sulfuric acid to the primary products, plus acetophenone and phenyl dimethyl carbinol. Other processes include sulfonation, chlorination of benzene, and oxidation of benzene. The compound is purified by rectification. 

Phenol production route Benzene sulfonation Benzene chlorination Benzene oxychlorinotion Cumene Alkylation me 1 hod Oxidation Toluene oxidation... 

Figure 6. Commercial activation of benzene by chlorine oxidation.

Another method for the hydrogenoiysis of aryl bromides and iodides is to use MeONa[696], The removal of chlorine and bromine from benzene rings is possible with MeOH under basic conditions by use of dippp as a ligand[697]. The reduction is explained by the formation of the phenylpalladium methoxide 812, which undergoes elimination of /i-hydrogen to form benzene, and MeOH is oxidized to formaldehyde. Based on this mechanistic consideration, reaction of alcohols with aryl halides has another application. For example, cyclohex-anol (813) is oxidized smoothly to cyclohexanone with bromobenzene under basic conditions[698]. 

Benzophenone is produced by the oxidation of diphenylmethane (350). This free from chlorine (FCC) route is favored for perfume uses. The Friedel-Crafts reaction of benzene and benzoyl chloride in the presence of aluminum chloride is also possible this reaction may proceed in the absence of catalyst at a temperature of 370°C and pressure of 1.4 MPa (351). 

The reddish brown pentachloride, uranium pentachloride [13470-21 -8], UCl, has been prepared in a similar fashion to UCl [10026-10-5] by reduction—chlorination of UO [1344-58-7] under flowing CCl, but at a lower temperature. Another synthetic approach which has been used is the oxidation of UCl by CI2. The pentachloride has been stmcturaHy characterized and consists of an edge-sharing bioctahedral dimer, U2CI2Q. The pentachloride decomposes in H2O and acid, is soluble in anhydrous alcohols, and insoluble in benzene and ethers. 

Ozone can be used to completely oxidize low concentrations of organics in aqueous streams or partially degrade compounds that are refractory or difficult to treat by other methods. Compounds that can be treated with ozone include alkanes, alcohols, ketones, aldehydes, phenols, benzene and its derivatives, and cyanide. Ozone readHy oxidizes cyanide to cyanate, however, further oxidation of the cyanate by ozone proceeds rather slowly and may require other oxidation treatment like alkaline chlorination to complete the degradation process. 

The only industrially important processes for the manufacturing of synthetic benzaldehyde involve the hydrolysis of benzal chloride [98-87-3] and the air oxidation of toluene. The hydrolysis of benzal chloride, which is produced by the side-chain chlorination of toluene, is the older of the two processes. It is no longer utilized ia the United States. Other processes, including the oxidation of benzyl alcohol, the reduction of benzoyl chloride, and the reaction of carbon monoxide and benzene, have been utilized ia the past, but they no longer have any iadustrial appHcation. 

The performance of many metal-ion catalysts can be enhanced by doping with cesium compounds. This is a result both of the low ionization potential of cesium and its abiUty to stabilize high oxidation states of transition-metal oxo anions (50). Catalyst doping is one of the principal commercial uses of cesium. Cesium is a more powerflil oxidant than potassium, which it can replace. The amount of replacement is often a matter of economic benefit. Cesium-doped catalysts are used for the production of styrene monomer from ethyl benzene at metal oxide contacts or from toluene and methanol as Cs-exchanged zeofltes ethylene oxide ammonoxidation, acrolein (methacrolein) acryflc acid (methacrylic acid) methyl methacrylate monomer methanol phthahc anhydride anthraquinone various olefins chlorinations in low pressure ammonia synthesis and in the conversion of SO2 to SO in sulfuric acid production. 

Oxidations usually proceed in the dark at or below room temperature in a variety of solvents ranging from aqueous bicarbonate to anhydrous benzene-pyridine. Base is quite commonly used to consume the hydrogen halide produced in the reaction, as this prevents the formation of high concentrations of bromine (or chlorine) by a secondary process. The reaction time varies from a few minutes to 24 hours or more depending on the nature of the reagent and the substrate. Thus one finds that NBS or NBA when used in aqueous acetone or dioxane are very mild, selective reagents. The rate of these oxidations is noticeably enhanced when Fbutyl alcohol is used as a solvent. In general, saturated, primary alcohols are inert and methanol is often used as a solvent. 

In aqueous pyridine solution, most diaryl sulphoxides may be oxidized to the corresponding sulphones with (dichloroiodo)benzene in reasonable yields103. The reaction involves nucleophilic attack by the sulphoxide on the electrophilic chlorine-containing species, yielding an intermediate chlorosulphonium ion which then reacts with water producing the sulphone. If the sulphoxide is optically active, then an optically active sulphone is produced in excellent optical yield when the reaction is carried out in oxygen-18 labelled water104, as indicated in equation (33). 

Mutations at the active site of CYPlOl (cytochrome P450j,j jj) from a strain of Pseudomonas putida made possible the monooxygenation of chlorinated benzenes with less than three substituents to chlorophenols, with concomitant NIH shifts for 1,3-dichlorobenzene (Jones et al. 2001). Further mutations made it possible to oxidize even pentachlorobenzene and hexachlorobenzene to pentachlorophenol (Chen et al. 2002). Integration of the genes encoding cytochrome PTSO. into Sphingobium chlorophenolicum enabled this strain to partially transform hexachlorobenzene to pentachlorophenol (Yan et al. 2006). 

Sulphoxides with -carboxylic acid groups are also converted to the corresponding sulphone by oxidation with (dichloroiodo)benzene (DCIB), which is a source of electrophilic chlorine . In this reaction the free acid group remains in the product. 

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