Toluene catalytic reactions

The main by-products ia the dehydrogenation reactor are toluene and benzene. The formation of toluene accounts for the biggest yield loss, ie, approximately 2% of the styrene produced when a high selectivity catalyst is used. Toluene is formed mostly from styrene by catalytic reactions such as the foUowiag ... 

The presence of soluble Rh nanoparticles after catalysis is demonstrated by TEM. The kinetic of the catalytic reaction was found to be zero-order in respect to the substrate and first order with respect to hydrogen and catalyst. Curiously, under the same conditions (60 °C, 7 bar H2), ethylcyclohexane is not detected at the end of phenylacetylene hydrogenation and the formation of methylcyclohexane from toluene was only obtained under drastic conditions 40 bar H2 and 80 °C. 

Catalytic Reactions. The copper catalysts were pre-reduced at 270°C with H2 before the catalytic test. Citral (0.1 g) was dissolved in toluene or heptane dehydrated over zeolites (8 ml) or not and the solution transferred under N2 into a glass reaction... 

Both catalytic reactions were investigated in the gas phase under atmospheric pressure using a glass fixed bed micro-reactor Prior to the reaction given amount of the catalyst (fraction 0.5-0.71 mm) was in situ activated at 500 °C for 2 h (N2 stream 40 ml min"1) In the case of toluene disproportionation the reaction temperature was 500 °C, WHSV 2-20 h"1, concentration of toluene in a stream was 18.5 mol%. Toluene alkylation was studied at the reaction temperature 250 °C. WHSV related to toluene was 10 h"1, concentration of toluene was 18.5 mol% and toluene to isopropyl alcohol molar ratio was 9.6. 

The most fundamental reaction is the alkylation of benzene with ethene.38,38a-38c Arylation of inactivated alkenes with inactivated arenes proceeds with the aid of a binuclear Ir(m) catalyst, [Ir(/x-acac-0,0,C3)(acac-0,0)(acac-C3)]2, to afford anti-Markovnikov hydroarylation products (Equation (33)). The iridium-catalyzed reaction of benzene with ethene at 180 °G for 3 h gives ethylbenzene (TN = 455, TOF = 0.0421 s 1). The reaction of benzene with propene leads to the formation of /z-propylbenzene and isopropylbenzene in 61% and 39% selectivities (TN = 13, TOF = 0.0110s-1). The catalytic reaction of the dinuclear Ir complex is shown to proceed via the formation of a mononuclear bis-acac-0,0 phenyl-Ir(m) species.388 The interesting aspect is the lack of /3-hydride elimination from the aryliridium intermediates giving the olefinic products. The reaction of substituted arenes with olefins provides a mixture of regioisomers. For example, the reaction of toluene with ethene affords m- and />-isomers in 63% and 37% selectivity, respectively. 

Linn and Halpern later found that the active catalyst in the ketone and anthracene hydrogenation reactions of Pez was likely to be Ru( 2-H2)(H)2(PPh3)3 (Fig. 3.6) [67]. For example, cyclohexanone is converted to cyclohexanol under mild conditions in toluene (see Table 3.3). The TOF depends on the substrate concentration, and the rate law for the catalytic reaction was determined to be given by Eq. (2), with k= 1.3x 10 M-1 s-1 at 20°C. 

Treatment of a solution of 55cCu(OTf)2 complex with a stoichiometric amount of PhI=NTs in CH2C12 resulted in rapid uptake of the insoluble iodinane. This complex, when treated with styrene, provided aziridine in quantitative yield in the same selectivity (37% ee) as the catalytic reaction (in CH2C12 at 25°C, 36% ee), Eq. 59. Addition of toluene at -78°C resulted in deposition of the complex as an oil. Analysis of the supernatant liquid revealed that <5% Phi was present, suggesting that the iodobenzene was still part of the complex. Unfortunately, this material resisted repeated attempts at crystallization. Whatever its true nature, it seems that this complex is not a classical copper nitrenoid (77). 

Indeed, both phosphines were strongly thermomorphic, particularly with respect to the less polar solvent n-octane. Between 20 and 80 °C, the sol-ubiUty of 5a increased ca. 60-fold. Between 20 and 100 °C, the increase was 150-fold. More important were the low absolute concentrations at lower temperatures. Very httle 5a could be detected in n-octane at - 20 or 0 °C (0.104 and 0.308 mM). At 20 °C, milUmolar concentration levels were present (1.13 mM). The low temperature limits were similar for the more polar solvents toluene and chlorobenzene (Fig. 2). Although the solubiUties did not increase as much with temperature, note that those at 65 °C (> 6.5 mM) are sufficient for all of the catalytic reactions described below. 

Cyclopropanation is an important synthetic method, and enantioselective catalytic reactions of olefins and diazoacetates provide access to valuable products with biological activity. In general, these reactions are conducted in anhydrous solvents and in several cases water was found to diminish the rate or selectivity (or both) of a given process. Therefore it came as a surprise, that the Cyclopropanation of styrene with (+)- or (-)-menthyl diazoacetates, catalyzed by a water-soluble Ru-complex with a chiral bis(hydroxymethyldihydrooxazolyl)pyridine (hm-pybox) ligand proceeded not only faster but with much Wgher enantioselectivity (up to 97 % e.e.) than the analogous reactions in neat THF or toluene(8-28 % e.e.) (Scheme 6.34) [72]. The fine yields and enantioselectivities may be the results of an accidental favourable match of the steric and electronic properties of hm-pybox and those of the menthyl-dizaoacetates, since the hydroxyethyl or isopropyl derivatives of the ligand proved to be inferior to the hydroxymethyl compound. Nevertheless, this is the first catalytic aqueous cyclopropanation which may open the way to other similar reactions in aqueous media. 

As the data summarized in Table 7 indicate, less polar toluene is prone to promote transformation among the species 5 6 7 8, 9, i.e., from a species of a higher coordination number of triphenylphosphine to a lower number. In acetone on the other hand, the quantity of species 5-7 is more sustained even at higher ratios of 4a to Rh (i.e., more similar to the catalytic reaction). 

This agrees with the theory that resonance-nonstabilized primary carban-ions are more stable than the corresponding secondary or tertiary carb-anions, whereas tertiary carbonium ions or radicals are more stable than the corresponding secondary and primary species. If radical intermediates were involved in a chain catalytic reaction of toluene with propylene, n-butylbenzene would be the product. 

Catalytic tests were performed in a glass vessel equipped with a stirrer motor. Two monoliths (diameter 4.3 cm, length 4 cm) were mounted in plane on the stirrer axis. The total reaction volume was 2.5 1. Lipase was assayed in the acylation of vinyl acetate with butanol in toluene. Initial reaction rate was followed by GC analysis. Immobilized trypsin was used in the hydrolysis of N-benzoyl-l-arginine ethyl ester (BAEE) in a 0.01 M phosphate buffer pH 8 at 308 K. The reaction was followed by UV-VIS at 253 nm, and reaction rate was calculated in the mass transfer limited situation. 

The catalytic reaction involves reaction of the naphthalenyl bromide and the Cirignard reagent together with 6 mol % of the nickel chloride complex of the ligand in diethyl ether/toluene at... 

The [2+2+1] cycloaddition of an alkene, an alkyne and carbon monoxide is commonly known as the Pauson-Khand reaction. This transformation has been adopted many times in the synthesis of complex natural products and related compounds, which contain a cyclopentenone moiety, for example, prostaglandins. Two independent reports of this reaction appeared almost simultaneously in late 2002 by Iqbal and co-workers25 and Fisher and co-workers26, respectively. They not only used very similar substrate systems in their studies, but they also reached very similar conclusions Toluene was found to be the preferred solvent in this reaction, even though it is a very poor microwave absorber. A reaction time between 5 and 10 min, using dicob alto ctacar-bonyl or dicobalthexacarbonyl as the carbon monoxide source, and a temperature of 100-120°C resulted in high yields of the products. Fisher and co-workers used 20 mol% Co2(CO)8 and cyclohexylamine as an additive (Scheme 5.12), since this system had been used previously in order to allow a catalytic reaction. Iqbal and co-workers did not use cyclohexylamine, but instead used 1 equiv. of the carbon monoxide (Co2(CO)6) source. In both reports, the products were formed in 40-70% yield. 

These results strongly pointed toward the involvement of the acidic hydroxyl groups in the catalytic reaction as suggested by Benesi (157), since the maximum activity was obtained when the zeolite was completely deammoniated. In addition, catalysts which had been dehydroxylated by high-temperature calcination demonstrated low activity. Thus, Benesi proposed that the Brtfnsted acid sites rather than the Lewis acids were the seat of activity for toluene disproportionation. This conclusion was supported by the enhancement in toluene disproportionation activity observed when the dehydroxylated (Lewis acid) Y zeolite was exposed to small quantities of water. As discussed previously, Ward s IR studies (156) indicated a substantial increase in Brdnsted acidity upon rehydration of dehydroxylated Y sieve. 

The tungsten(II) carbonyl complex (CO)4W(/u.-Cl)3W(SnCl3)(CO)3 has been identified as a very effective catalyst for the hydroarylation of norbornene conducted in arene solution at room temperature. Norbornene adducts with benzene, toluene, p-xylene, and mesitylene have been isolated. On the basis of XH NMR monitoring of several catalytic reactions, a possible mechanism, involving coordination of norbornene to the W(II) atom and its activation, has been proposed.123... 

Catalytic Reactions. As the techniques for solid-state n.m.r. continue to improve with the simultaneous improvement in sensitivity and hence speed, there will be a growing trend to look at chemical reactions occurring on or in catalysts. There have already been a number of instances where catalytically stimulated reactions have been studied by 13C n.m.r. - the alkylation of toluene by methanol on X zeolite, for example,138 in which the influence of the cation, Na+ or Cs+, on selectivity was deduced. The adsorption binding and decomposition of various metal carbonyls on A1203 or in zeolites has been studied,139 likewise, the nature and sites of interaction of CO and C02 on X and Y zeolites.140... 

An application of the fluorous two-phase system to catalytic reactions is the hydro-formylation of terminal olefins with CO and H2 [5]. Aldehydes 1 can be isolated, together with the branched side products 2. In the Q,FiiCF3/toluene solvent mixture, the catalyst [HRh(CO) P[CH2CH2(CF2)5CF3]3 3] is obtained in situ. It acts in the hydroformylation reaction at 100 °C and can be separated afterwards in the fluorous phase. In this process, however, approximately 0.5% of the catalyst remains in the organic phase. Furthermore, the lower solubility of CO and H2 in the fluorous phase produces a lower catalyst activity. Accordingly, the hydroformylation of ethene can be conducted in a continuous process in an autoclave. 

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