Benzenes cyclohexenes from

Write a reasonable mechanism for the formation of cyclohexyl benzene from the reaction of benzene cyclohexene and sulfuric acid J... 

Cyclohexane, produced from the partial hydrogenation of benzene [71-43-2] also can be used as the feedstock for A manufacture. Such a process involves selective hydrogenation of benzene to cyclohexene, separation of the cyclohexene from unreacted benzene and cyclohexane (produced from over-hydrogenation of the benzene), and hydration of the cyclohexane to A. Asahi has obtained numerous patents on such a process and is in the process of commercialization (85,86). Indicated reaction conditions for the partial hydrogenation are 100—200°C and 1—10 kPa (0.1—1.5 psi) with a Ru or zinc-promoted Ru catalyst (87—90). The hydration reaction uses zeotites as catalyst in a two-phase system. Cyclohexene diffuses into an aqueous phase containing the zeotites and there is hydrated to A. The A then is extracted back into the organic phase. Reaction temperature is 90—150°C and reactor residence time is 30 min (91—94). 

A more detailed study of this system using benzene and toluene has been reported by Soede et al. (1993) from The Netherlands. They have shown that the role of ZnS04 is to make the Ru hydrophlilic so that the catalyst particles are surrounded by a stagnant water layer. This aids in the rapid removal of the cyclohexene from the catalyst surface to the organic phase. The reaction is operated in mass transfer controlled conditions. 

Table 4 shows that benzene is formed at almost identical rates from cyclohexene, hexadiene, methylcyclohexene and cyclohexadiene react under low partial pressure over Ga-HZSM-5. which suggests that over these catalysts benzene is formed from the same intermediate. In contrast over H-ZSM-5, under identical experimental conditions, the rate of benzene formation from the hydrocarbons cited was one to two orders of magnitude lower. These results prove again that gallium plays a decisive role in aromatization. Over H-ZSM-5 the major hydrocarbon formed is methylcyclopentene from cyclohexene (ring contraction)... 

The excess molar enthalpies at 323 K and 1.3 MPa were measured in [64] for hydrocarbons (hex-l-ene, cyclohexane, benzene, and cyclohexene) in the [C2Cilm][Tf2Nj. The negative excess enthalpies were observed (-730 J mol at Xh = 0.63) only in the mixtures with benzene, expected from the discussion about the interactions in the solution. Much more data can be found in the two existing data banks [1,2] for example, in Dortmund Data Bank, 37 systems are accessible. 

Ruthenium is the most selective metal to produce intermediate olefins. Certain catalyst additives and water100-102 increase the yield of cyclohexene from benzene up to 48% at 60% conversion.103 Alkylbenzenes are hydrogenated at somewhat lower rates then benzene itself. As a general rule the rate of hydrogenation decreases as the number of substituents increases, and the more symmetrically substituted compounds react faster than those with substituents arranged with less symmetry.9,10 Highly substituted strained aromatics tend to undergo ready saturation, even over the less active palladium. 

Voorhoeve et al. did not study HDS directly but rather the hydrogenation of benzene and cyclohexene in the presence of CS2 were studied. It was found that Ni strongly promoted the hydrogenation of benzene but only weakly the hydrogenation of cyclohexene. From other evidence, they concluded that the active sites were unsaturated W3+ with different degrees of... 

Fig. 25. Inhibition of benzene (O) from cyclohexane and increasing cyclohexene formation ( ) with time on Pt(S)-[6(111) x (100)] surface. All catalysts with (111) orientation terraces behave similarly. T, 150°C 4 x 10 8 Torr reactant H2 HC, 20 1.

Fig. 27. Inhibition of benzene formation from cyclohexene on disordered carbonaceous...

In terms of the individual compounds found in the condensable products, as with conventional pyrolysis, a-alkenes alkanes and dialkenes were the most abundant compounds. A large number of other aliphatic and aromatic compounds ranging from C3 to approximately 55 were also found, including methylcyclopentene, benzene, cyclohexene, toluene, ethylbenzene, xylene, propylbenzene and methyl-ethylbenzene. The analysis also showed that the condensables obtained at 500 and 700°C, although possessing similar levels of cleavage, showed important differences in the individual compounds present [85],... 

Ruthenium was recognized early to be the catalyst which produced the largest amount of the intermediate cyclohexene from the xylenes, rhodium and platinum giving decreasing amounts. The importance of water in maximizing the yield of cyclohexene using ruthenium as catalyst was demonstrated by Don and Scholten." A recent patent application claims yields of 48% cyclohexene at 60% conversion of the benzene. ... 

Selective Hydrogenation of Benzene to Cyclohexene Obtaining trans substituted cyclohexanes suggested that desorbed cyclohexenes were intermediates in the hydrogenation of benzenes. The isolation of cyclohexene and substituted cyclohexenes from the hydrogenation of benzene and substituted benzenes was first reported for hydrogenations run over a Ru/C catalyst, but the maximum olefin concentrations observed in this early work were only 0.2-3.4%.7... 

An excellent alternative to the classical Hunsdiecker reaction and its variants, which totally avoids the use of heavy metal salts and potent electrophilic reagents, consists of the simple photolysis or thermolysis of Barton esters in refluxing bromotri-chloromethane for the bromides or tetrachloromethane for the chlorides [4], The analogous decarboxylative iodination can also be achieved using iodoform as the reagent in a benzene/cyclohexene solvent system (Scheme 5). For the cases of vinylic and aromatic acids, where the usual problems of chain efficiency are encountered, the addition of azobisisobutyronitrile (AIBN) is also required [10]. Nevertheless, since this method can operate on both electron-rich and electron-poor aromatic systems, and moreover does not suffer from the competitive electrophilic aromatic bromination found with electron rich aromatics under normal Hunsdiecker conditions, this route to synthetically useful aryl iodides and bromides should find widespread application. 

On the bases of the results and discussion stated above, we considered the role of water for the formation of cyclohexene (Fig.5). In the reaction mixture, the catalysts are in aqueous phase, and benzene and hydrogen have to pass the thick water layer surrounding the catalysts to react with each other on the active sites. When cyclohexene is produced from benzene, it is expelled by water and benzene newly coming from organic phase. High temperatures and pressures such as 170-190 °C and 60-80 kg/cm which are the optimum conditions for the production of cyclohexene are favorable for increasing the concentration of benzene in the water layer. If the desorption rate of cyclohexene from the surface is slow, cyclohexene is naturally converted to cyclohexane. But, if cyclohexene is expelled, it will be isolated from the active sites in the catalysts because of its low solubility to water. Accordingly, it could... 

Cyclohexadiene was converted totally on a Ni catalyst when the benzene conversion was - 5-6%. From this point onwards, the concentration of cH dropped dramatically with a simultaneous increase in its specific radioactivity exceeding that of cH, when the Bz conversion reached 10% as shown in Fig. 3. The formation of radioactive cyclohexene from [ C]-benzene supplied further evidence of the existence of stepwise hydrogenation, even if it is not the exclusive route. 

Labeled benzene ring from 1,5-dlbromldes and labeled carboxylic acid esters via cyclohexanols and cyclohexenes... 

Terpolymer samples (0.6-0.7 mg) were pyrolysed at 550 °C and 600 °C. The major products of pyrolysis were found to be ethylene, propylene, butadiene, benzene, toluene, and vinyl cyclohexene from the butadiene part, and acrylonitrile and acetonitrile from the acrylonitrile part of the polymers. 

Based on the data for complexation of arenes with Ag+ ion in water, the separation of arenes from alkanes and of arene mixtures would seem an unlikely use of Ag+-Nafion membranes (see equations 1-3). As an example, the equilibrium constants for 1-nexene, cyclohexene, and benzene with Ag+ in water are 860, 79, and 2.4, respectively(2). Even though the trend in aqueous solubilities for these three components is opposite to the trend in Ken s, it is not obvious that large fluxes for solutes like benzene would be obtained. Nevertheless, for a bicomponent feed solution of benzene and methylcyclohexane (0.5 M each in isooctane), a separation factor S(benzene/methylcyclohexane) greater than 750 is obtained. An even more illustrative example is a tricomponent feed solution containing benzene, cyclohexene and cyclohexane (0.5 M each) where the observed fluxes are 3.9 x 10-, 7.3 x 10- and <0.01 x 10-9 mol cm-2 s-l, respectively. Even though the Keq s for benzene and cyclohexene differ by a factor of over 30, their fluxes through Ag+-Nafion membranes differ by less than a factor of 2. 

Phenol Vi Cyclohexene. In 1989 Mitsui Petrochemicals developed a process in which phenol was produced from cyclohexene. In this process, benzene is partially hydrogenated to cyclohexene in the presence of water and a mthenium-containing catalyst. The cyclohexene then reacts with water to form cyclohexanol or oxygen to form cyclohexanone. The cyclohexanol or cyclohexanone is then dehydrogenated to phenol. No phenol plants have been built employing this process. 

The mechanism of the reaction is unknown. The stereospecificity observed with (E)- and (Z)-l-methyl-2-phenylethylene points to a one-step reaction. The very low Hammett constant, -0.43, determined with phenylethylenes substituted in the benzene ring, excludes polar intermediates. Yields of only a few percent are obtained in the reaction of aliphatic alkenes with (52). In the reaction of cyclohexene with (52), further amination of the aziridine to aminoaziridine (99) is observed. Instead of diphenylazirine, diphenylacetonitrile (100) is formed from diphenylacetylene by NH uptake from (52) and phenyl migration. 

The reaction of an alicyclic enamine with benzyne intermediate yields simple arylation products and/or 1,2-cycloaddition products, depending upon the reaction conditions 102). This is illustrated by the reaction of l-(N-pyrrolidino)cyclohexene with benzyne (86) (obtained from fluoro-benzene and butyl lithium or o-bromofluorobenzene and lithium amalgam), which produces benzocyclobutene 87 102). 

A mixture of 100 g (0.6 mole) of 1-morpholino-l-cyclohexene, 28.8 g (0,4 mole) of /3-propiolactone, and 100 ml of chlorobenzene is placed in a 500-ml round-bottom flask fitted with a condenser (drying tube). The mixture is refluxed for 4 hours. The solvent and excess enamine are removed by distillation at aspirator pressure. (The residue may be distilled to afford the pure morpholide, bp 187-18871 rnm, 1.5090.) Basic hydrolysis may be carried out on the undistilled morpholide. To the crude amide is added 400 ml of 10% sodium hydroxide solution. The mixture is cautiously brought to reflux, and refluxing is continued for 2 hours. The cooled reaction mixture is made acidic (pH 4) and is extracted three times with ether. The combined ether extracts are washed twice with 5 % hydrochloric acid solution and twice with water. The ethereal solution is dried (sodium sulfate), then filtered, and the solvent is removed (rotary evaporator). The residue may be recrystallized from petroleum ether-benzene, mp 64°. 

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