Toluene, metalation

The used catalysts were washed with toluene in a Soxhlet extractor, stored in purified toluene and dried before analysis. C, H, S and N elemental analysis were performed by combustion using a Carlo Erba apparatus. The coke content is therefore defined in this work as being the carbon content of a used catalyst washed by hot toluene. Metal contents were measured by X-ray fluorescence spectroscopy. The coke hydrogen content was determined by difference between the hydrogen content measured for the used catalyst and the hydrogen content measured for the fresh NiMo catalyst (0.6 wt %). 

Optimum Conditions for Preparing Benzyllithium from Toluene. Both the TMEDA and TED complexes of benzyllithium were investigated. Toluene metalation proceeds much faster than does benzene metalation under similar conditions. The benzyllithium complexes were more soluble in hydrocarbon solvents than were the corresponding phenyllithium complexes. This method of preparation of benzyllithium is the most convenient of the few literature procedures available. Other procedures described are the cleavage of benzyl methyl ether with lithium... 

Only a brief study was made of the metalation rate of toluene by n-butyllithium because the reaction proceeded readily with TMEDA under most conditions. The runs listed in Table IV indicate just how much faster toluene metalation proceeded compared with benzene metalation. This rate was about 6.5 times faster with hexane as the solvent and at least 10 times faster when the corresponding aromatics (toluene and benzene) were used as the solvents. 

Because toluene metalation is very fast, the best preparative procedure is to slowly add TMEDA to n-butyllithium in toluene at about 60 °C because of the need to drive off butane as it forms and prevent its build-up in the reaction solution. The reaction is quite exothermic because of the initial solvation of TMEDA. In small-scale preparations (200-ml or less) this precaution is not necessary. An added benefit of adding the TMEDA at a steady rate to the warm solution is that the reaction rate is almost instantly controllable and readily followed by observing the rate of gas evolution. Concentrations of n-butyllithium in toluene to about 26 wt % could be used without having to add additional toluene to ensure product solubility. 

The toluene-metalation system in this study differs from that of Broaddus in that pure toluene was used as the solvent a RLi to TMEDA ratio of two was used. Analyses were usually run after complete reaction of the n-butyllithium unless otherwise noted. Higher reaction temperatures were used, and the final concentration of benzyllithium in solution was higher. 

In those studies that use solvents other than the hydrocarbon corresponding to the carbanion, any metalation of the solvent would change the nature of the conductive species and complicate data interpretation. For example, the pKa s of toluene (35) and diphenylmethane ca. 33) are close enough so that toluene metalation by diphenylmethyllithium could be significant at very low concentrations of the lithium compound according to the equilibrium ... 

Figure 22.1. Toluene conversion and selectivity to partial oxidation products. Reaction conditions 160°C, 0.1 MPap02, 20 ml toluene, 0.8 g of catalyst (1 wt% AuPd/C prepared by sol-immobilisation with 1 1.85 Au/Pd ratio), toluene/metal molar ratio of 3,250 and reaction time 110 h. Key o conversion, selectivity to benzyl alcohol, selectivity to benzaldehyde, selectivity to benzoic acid, selectivity to benzyl benzoate.

Studying these reactions in solution by quenching with electrophilic iodine revealed that while the weta-metalated product was the major product (73%), a small amount of ortho-metalation (6%) and para-metalation (21%) had also occurred [62]. The wefa-metalation of toluene can also be accomplished using the heteroleptic sodium magnesiate TMEDA-Na(TMP)(nBu)Mg(TMP) (Fig. 16) [63]. This base operates synergically via overall alkyl basicity to yield a discrete molecular framework containing a bridging molecule of toluene, metalated at the meta position [64]. 

Toluene-/ sulplionamide is almost insolubb in cold water, but dissolves readily in sodium hydroxide solution (as the sodium derivative) aid is immediately reprecipitated on the addition of strong acids. To show the formation of the sodium derivative, dissolve about o-2 g. of metallic sodium in about 10 ml, of ethanol, cool the solution, and then add it to a solution of 1 g. of the sulphonamide in 20 ml. of cold edianol. On shaking the mixture, fine white crystals of the sodium derivative, CH,C,HjSO,NHNa, rapidly separate, and may be obtained pure by filtering at the pump, and washing firet with a few ml. of ethanol, and then with ether. 

In the second, a trace of toluene (possibly formed by hydrolysis) is metalated by the p-tolyl-sodium to give benzyl-sodium and toluene. Since the toluene is regenerated in the reaction, a small quantity would be adequate as a sort of catalyst. 

CbHOROCARBONSANDCbHOROHYDROCARBONS - RDIG-CbHORINATED TOLUENES] (Vol 6) -in platinum-group metal complexes pLATINUM-GROUP METALS, COMPOUNDS] (Vol 19)... 

Historically, the isomerization catalysts have included amorphous siUca-aluminas, zeoHtes, and metal-loaded oxides. AH of the catalysts contain acidity, which isomerizes the xylenes and if strong enough can also crack the EB and xylenes to benzene and toluene. Dual functional catalysts additionally contain a metal that is capable of converting EB to xylenes. 

In the presence of alkah metals such as potassium and sodium, toluene is alkylated with ethylene on the methyl group to yield, successively, normal propylbenzene, 3-phenylpentane, and S-ethji-S-phenylpentane (21). 

C and 5 kg/cm pressure (see Molecularsieves). Selectivity for toluene and xylenes peaks at 550°C but continues with increasing temperature for hensene. The Cyclar process (Fig. 6) developed joindy by BP and UOP uses a spherical, proprietary seoHte catalyst with a nonnoble metallic promoter to convert C or C paraffins to aromatics. The drawback to the process economics is the production of fuel gas, alow value by-product. BP operated a... 

The low temperature limitation of homogeneous catalysis has been overcome with heterogeneous catalysts such as modified Ziegler-Natta (28) sohd-supported protonic acids (29,30) and metal oxides (31). Temperatures as high as 80°C in toluene can be employed to yield, for example, crystalline... 

Today, the air oxidation of toluene is the source of most of the world s synthetic benzaldehyde. Both vapor- and Hquid-phase air oxidation processes have been used. In the vapor-phase process, a mixture of air and toluene vapor is passed over a catalyst consisting of the oxides of uranium, molybdenum, or related metals. High temperatures and short contact times are essential to maximize yields. Small amounts of copper oxide maybe added to the catalyst mixture to reduce formation of by-product maleic anhydride. 

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